The body snatchers

By Athayde Tonhasca

Family feuds abound in history and in the tabloids, but things got really out of hand with the offspring of Egyptian gods Geb (Earth) and Nut (sky). As the first-born, Osiris was naturally chosen to be the ruler of the world. But his brother Set didn’t care one bit for this undemocratic arrangement, so he decided to despatch Osiris to the Underworld. Set set out a murderous plan worthy of an Agatha Christie story; he commissioned a beautiful casket, tailored to fit a body with Osiris’ exact measurements. Set then organised a magnificent banquet, inviting heavenly celebrities and bro Osiris. When they were all done with the eating and drinking, Set announced a surprise. The casket was brought in, and the host told his guests that whoever could fit inside, could take it home (an odd gift to us, perhaps, but who are we to judge Egyptian gods?). One by one the guests climbed into the casket, which was too small or too big – until Osiris had a go at it. He laid down inside the casket, which, to his glee, fit him perfectly. Set’s trap was set; he slammed the casket’s lid shut and locked it, killing his sibling. Later Set retrieved Osiris’ body and chopped it into small pieces.

The Mummy (1932) escaped from his sarcophagus, but no such luck for Osiris. Art by Karoly Grosz, Wikimedia Commons.

Set’s shenanigans were the perfect inspiration for naming a new species from the genus Euderus, a small group of parasitic wasps in the family Eulophidae. Most Euderus species are moth and beetle parasitoids, but the wasp discovered by Egan et al. (2017) in Florida (USA) is peculiar, to say the least. Its host, Bassettia pallida, is itself a parasitic wasp, but of a different kind: this species is one of the many gall wasps or cynipids (family Cynipidae), which lay their eggs in oaks (Quercus spp.) and less commonly in related plants (family Fagaceae). The egg-laying induces the plant to produce a gall, which is an abnormal growth resulting from increased size or number of cells (galls can also be caused by tissue feeding or infections by bacteria, viruses, fungi and nematodes). Cynipids trigger their host plants to produce nutritious tissue inside their galls, which become ideal places for a larva to grow: there’s nothing better for one’s survival than a cosy, safe and nourishing nursery.

Oak galls or oak apples, growths resulting from chemicals injected by the larva of gall wasps © Maksim, Wikimedia Commons.

In the case of B. pallida, it induces the formation of galls inside stems of sand live oak (Q. geminata) and southern live oak (Q. virginiana). Each of these galls is called a ‘crypt’. So appropriately, B. pallida is known as the crypt gall wasp. When the adult wasp completes its development, it chews an exit hole from inside its woody quarters and flies away.

(a): a crypt gall wasp; (e): adults’ exit holes © Weinersmith et al., 2020.

Life looked good for the crypt gall wasp in the southeastern United States – until we learned about the machinations of its recently discovered enemy. The Eulophidae parasitoid locates a crypt and pierces it with its ovipositor, laying an egg inside the chamber, near or into the developing crypt gall wasp. We don’t know exactly what goes on inside the chamber, but the outcome is not good at all for the crypt gall wasp. When it tries to chew its way out, it’s no longer able to create a hole big enough to fit its body: the wasp becomes entrapped inside its crypt, Osiris-like. During its failed attempt to get out, its head blocks the exit hole. All the better for the parasitoid larva that hatched inside the crypt: it can feed at leisure on the host’s weakened body. On completing its development, the adult parasitoid wasp chews through the host’s head plug and comes out to the big wide world. So there was no better name for this species than Euderus set, the crypt-keeper wasp.

(c): a crypt-keeper wasp pupa in a chamber made by a crypt gall wasp; (f): an exit hole plugged by the head capsule of a dead or dying crypt gall wasp; (g): a crypt gall wasp head capsule chewed through by an exiting crypt-keeper wasp © Weinersmith et al., 2020.

The relationships between oaks and these wasps are examples of host manipulation, which happens when a parasite influences the host’s behaviour or physiology to its (the parasite’s) advantage. The crypt gall wasp induces its host plants to produce galls for its benefit, and in turn the crypt-keeper wasp forces its host into becoming trapped and an easy meal for the parasitoid’s larva: the manipulation of a manipulator is known as a hyper-manipulation, an uncommon phenomenon.

A female crypt-keeper wasp, a hyper-manipulator © Egan et al., Wikimedia Commons.

There are many cases of host manipulation, and the zombie-ant fungus described by the co-author of the theory of evolution by natural selection Alfred Russel Wallace (1823-1913) is one of the better known. This fungus (Ophiocordyceps unilateralis) induces its host ants to climb up the vegetation and clamp their mandibles around a twig or leaf vein. An infected ant will stay put, rain or shine, while the fungus grows inside it. After 4-10 days the ant dies, the fungus grows a ‘stalk’ (stroma) from the ant’s head and releases spores that will infect ants walking about on the forest floor.

A dead Camponotus leonardi ant attached to a leaf vein. The stroma of a zombie-ant fungus emerges from the back of the ant’s head © Pontoppidan et al., 2009.

The more researchers look into it, the more they find cases of host manipulators such as the Darwin wasps Hymenoepimecis spp., which parasitize several species of orb-weaving spiders in the Neotropical region. A female wasp stings and temporarily paralyses her victim, laying an egg on its abdomen. The emerging larva bites through the spider’s cuticle and feeds on its ‘blood’ (haemolymph). The spider carries on with its life, building webs and catching prey, but the growing parasitoid takes its toll; eventually it kills its host. 

L: A H. heidyae egg attached to a Kapogea cyrtophoroides. R: Third instar H. heidyae larva feeding on a recently killed spider; the inset shows details of the dorsal hooks used by the larva to cling to its host © Barrantes et al., 2008.

But shortly before the spider’s demise, somehow – probably by hormone injection – the larva takes command of the host’s behaviour. The spider builds a cocoon web made of thickly woven silk, which doesn’t look at all like a normal web. The spider dies, the larva enters the cocoon and completes its development. Some days later, the adult wasp emerges and flies away.

a. A normal K. cyrtophoroides web; b. The web’s hub; c. A cocoon web induced by the parasitoid;
d.Central section of the cocoon web and the wasp’s cocoon © Barrantes et al., 2008.

Parasitic wasps are not deterred by the defences of hosts such as Anelosimus eximius. This is one of the few species of social spiders; they build massive tent-like nests that shelter hundreds or thousands of individuals, who hunt together in raiding packs and even cooperate in raising their young (watch their comings and goings). But in the Amazon region, A. eximius can’t evade the Darwin wasp Zatypota sp. A parasitized spider leaves the colony and builds its own cocoon-like web. It then becomes immobilised, so that the wasp larva can unhurriedly consume it. When finished with its meal, the larva enters the cocoon to complete its development. The larger the spider colony, the more chances of being parasitized; up to 2% of individuals become hosts to the parasitoid (Fernandez-Fournier et al., 2018).  

L: A group of A. eximius in a communal web © Bernard Dupont, Wikimedia Commons. R: A 5-m long, 3-m high colony of A. eximius; photo by A. Bernard © Krafft & Cookson, 2012.

A fierce looking H. neotropica and its larva feeding on an Araneus omnicolor © Sobczak et al., 2012.

Host manipulation seems to be much more common than we thought, so we shouldn’t expect pollinators to be safe from it. And they are not. The conopid fly (family Conopidae) Physocephala tibialis forces bumble bee hosts to bury themselves in the soil just before dying. The nematode worm Sphaerularia bombi, found throughout the northern hemisphere and South America, infects queens of several bumble bee species, castrating its host. And at least for the buff-tailed bumble bee (Bombus terrestris), the nematode also alters the bee’s behaviour (Kadoya & Ishii, 2015). An infected queen feeds normally, but does not breed or build a nest. Instead, she keeps flying into the early summer months, and by doing so she unintentionally helps to spread the nematode. Certainly many other cases of pollinators’ manipulation by parasites wait to be discovered because their effects can be subtle and inconspicuous.

CSI Garden: a post-mortem examination of a buff-tailed bumble bee found dying on a roadside pavement in England revealed an infestation by the host manipulator S. bombi © The Encyclopedia of Life.

Host manipulation can be seen as a form of extended phenotype (Dawkins, 1982; phenotype refers to a species’ observable characteristics resulting from the expression of its genes). By changing the host’s behaviour for its own benefit, the parasitoid – ultimately, its genes – expresses its phenotype in the world at large. In Dawkins’ own words, ‘an animal’s behaviour tends to maximize the survival of the genes “for” that behaviour, whether or not those genes happen to be in the body of the particular animal performing it’. The phenomenon would have deep consequences for natural selection, but the extent of extended phenotypes has been debated since the publication of Dawkins’ book. 

If you are smugly assuming that behavioural puppeteering is for lower animals such as insects, you’d better think again. Some studies suggest that rodents infected with the protozoan Toxoplasma gondii become more active but sluggish in reacting to alarm signals; worse, they may become attracted to the smell of cat’s urine. If so, an infected mouse has a good chance of prematurely ending its days in a moggie’s maw – which was T. gondii‘s ‘intention’ all along, since cats are its ultimate host. And the plot thickens: infected cats excrete T. gondii spores in their faeces, which can make their way into other mammals. A 26-year study with grey wolves (Canis lupus) from Yellowstone National Park, Wyoming, USA, revealed that infected individuals – probably the result of contact with pumas (Puma concolor) – are bolder, more likely to become pack leaders and have better chances of reproducing (Meyer et al., 2022). In humans, toxoplasmosis, the infection caused by T. gondii, is widespread but usually does not have any symptoms. Most people don’t even know they have it, but all sorts of behaviour and mental disorders such as heightened aggression and Parkinson’s disease have been linked to the infection. The effects of T. gondii on rodents and humans have been disputed because data often show weak, inconclusive or no effects (Johnson & Koshy, 2020). In any case, our invulnerability to the manipulative power of parasites should not be taken for granted. Rephrasing the quote misattributed to Margaret Mead, always remember that in biology, Homo sapiens is unique. Just like every other species.

Invasion of the Body Snatchers (1956). Art by Allied Artists Pictures Corporation. Wikimedia Commons.

Wake up, and smell the herbs

It is one of life’s great sensory pleasures. Running your hand through a herb and inhaling its distinctive aroma. Many of us grow herbs for that reason alone, and as many again plant herbs purely as a cooking ingredient. But there is another excellent reason to grow herbs – as pollinators’ food.

Thyme

Herbs have a few advantages over conventional flowers in your garden. This is especially so if you don’t have a lot of space. You might feel you have to compromise on garden thrills, but herbs do well in containers and window boxes and offer a fantastic, colourful alternative. They also, by and large, thrive in drier conditions, thus the often potentially arid environment of a pot or container suits them well. So what’s not to like?  Herbs guarantee heady smells, handy cooking ingredients, low maintenance, lovely textures and colours, and of course pollinator food.

You might be persuaded to go down this route but hesitating over which herbs to plant.  Well the list is fairly impressive, and there is bound to be something to suit almost every taste. Oregano, mint, chives, borage, fennel, rosemary, lavender, thyme, lemon balm … 

Thyme is a proven versatile flavour – an excellent garnish on many foods. A reliable and robust little herbthat will return year on year, it is ideal for filling in cracks in a pavement or rockery. It is often used in meat, vegetable and fish dishes.

Sage is a mainstay of many a risotto dish, and who doesn’t like a sprig of rosemary in roast potatoes. To run your hand through a rosemary plant and then inhale is one of life’s great pleasures. The blue flowers are a bee magnet.

Chives, with their vivid purple pom-pom flowers, are another summer classic. They spruce up many a salad and go particularly well with the ever reliable potato. 

Chives

The blue flowers of borage are pleasantly distinctive and those small flowers suit bees with short tongues. It is one of the best flowers for bumblebees. If yellow is your colour, then the chances are you are familiar with fennel – mining bees and honeybees are drawn to it in good numbers. You will be amazed at how popular fennel is with hoverflies.

There is more to mint than meets the eye. Spearmint and peppermint are well known and strong flavours. The smell from even the gentlest rub of this plant is a delight and a unique aroma.  It’s a favourite element in a host of summer drinks. 

Lavender is probably the most photographed herb. Vast swaying seas of this attractive blue flower are the classic picture-postcard vision many associate with Provence in the South of France. If you stumble across a lavender field, be prepared for a knock-out smell and the gentle hum of thousands of bees. These blue oasis are as much a pollinator’s dream as a nature-lover’s feast. 

Lavender in Provence

You would be right it you think that I mention the Mediterranean with some longing. As we head into summer, it has a pull of its own and herbs are a big part of the experience. If you follow the sun in Europe then the chances are you will encounter herbs on your travels. If you go a little further south, to Morocco say, you might enjoy mint tea which is part and parcel of Moroccan culture. In Greece, Tzatziki relies on mint for flavouring and may come as a dip or a sauce. Back in Provence, your food experience has a strong chance of including the ever popular blend of herbs known as Herbs de Provence.

Home or away, there is a lot to enjoy in the world of herbs. And if you plant some around your doorstep you will be helping our hard-pressed pollinators big time. Don’t, whatever you do, be persuaded by culinary experts to trim your herbs before they flower – that would not go down well with your local pollinators.

Thorny issues

By Athayde Tonhasca

Once upon a time, so Charles Perrault (1628-1703) told us, a prince was out enjoying nature by merrily killing animals in the woods, when he spotted a hidden castle deep in the forest. The prince’s myrmidons explained that the castle housed a beautiful princess who had been cursed by an evil fairy; the young lady was to lay in a comatose state until awakened by a handsome prince. His Highness, who obviously had a high opinion of his looks, decided he was the person destined to break the spell. But getting to Sleeping Beauty wouldn’t be easy; the castle was surrounded by trees and a formidable obstacle that would have stopped a less determined hobbledehoy: a wall of brambles.

Having princely clothes ruined by brambles. The Sleeping Beauty, art by Arthur Rackham (1867–1939), Wikimedia Commons.

Brambles or blackberries comprise many species that are difficult to tell apart; over 300 of them have been recognized in the UK. These related species are known as micro-species, and for practical reasons they are treated collectively as a species complex or as an aggregate group (abbreviated as agg.). So we usually refer to brambles as Rubus fruticosus agg.

Natives to much of Europe, brambles are valued fruit crops when grown as blackberry varieties, but they are also invasive in some circumstances. Their dense thickets are barriers to amorous princes and roaming livestock, and their thorns hurt animals and contaminate wool. Thanks to their vigorous growth (watch their shoots thrusting ahead), brambles can outcompete other wild plants and curtail the development of tree saplings; if left unchecked, brambles can quickly alter the species composition and physical structure of some habitats. For those reasons, they are considered invasive weeds in Australia, New Zealand and the USA.

But as we have learned from many a definitive self-help book, problems are opportunities with thorns on them: several birds and small mammals nest or take shelter in bramble scrub. And their berries are food for sundry animals such as badgers, field mice, foxes, moths and voles: watch some of them having a nutritious fruit breakfast. Bramble berries are quite handy when other sources begin to dwindle in late summer and autumn.

A bramble thicket: barrier and shelter © Richard Humphrey, Wikimedia Commons.

But brambles have much more to offer; their open, bowl-shaped flowers, typical of the Rosaceae family, are easily accessible and produce large amounts of pollen and nectar, which are available during most of the season – usually from May to September in the UK. So a range of pollinators and other insects take advantage of these abundant and reliable food sources, from the European honey bee (Apis mellifera), which is one of the most enthusiastic visitors, to scarce species such as the brown-banded carder bee (Bombus humilis) (Wignall et al., 2020).

A welcoming bramble flower © Rosser1954, Wikimedia Commons.

Brambles have a flexible approach to reproduction. They commonly propagate vegetatively (no seeds are involved) by deploying ‘runners’, shoots that take root when they are touching the ground; they can resort to apomixis, which is the production of seeds without fertilisation; or less frequently, they can use the familiar sexual mechanism of pollen deposition. This diversified strategy helps explains brambles’ complex taxonomy. Plants generated by vegetative growth or apomixis are clones, genetically identical to the parent plant. When they do occasionally outcross and produce seeds from fertilized ovules, the resulting offspring will have genetic profiles slightly different from the parent plant. Given time, these variants become species marginally different from each other, which spread out as clones and readily hybridise (Clark & Jasieniuk, 2012). Untangling these species is a job for a small tribe of patient, dogged taxonomists dedicated to batology (from the Ancient Greek báton, ‘blackberry’): the scientific study of plants in the genus Rubus.

Although infrequent, sexual reproduction is important for maintaining brambles’ genetic diversity, and here insects play their part by cross-pollinating plants. Among brambles’ many flower visitors, several bees and flies have been considered candidates for the job. But this list is biased because it leaves out insects we don’t normally see collecting pollen or nectar – the nocturnal visitors, i.e., moths. And they should not be neglected. Like many other plants, brambles produce nectar with variable concentrations of sugars during the day, and their highest output happens to be from late afternoon into the evening. Such sugary bounty wasn’t likely to go unnoticed by the night shift wanderers. Anderson et al. (2023) reported a range of visitors to brambles flowers during the day (flies and bees, mostly); but at night, moths were almost alone in dropping by for a sip of nectar. But there was more; moths visited fewer flowers per hour than diurnal visitors, but they deposited more pollen grains on stigmas. That’s an important finding. Flower visitation is often – and incorrectly – associated with pollination. In fact, some visitors avoid pollen altogether, or manage to remove the pesky yellow grains from their bodies. Pollen deposition is a well-tested method to evaluate who is pollinating what.   

A tobacco hornworm (Manduca sexta) depositing pollen on a Colorado Springs evening primrose flower (Oenothera harringtonii) © Smith et al., 2022.

So here we are. Blackberry lovers notwithstanding, brambles are generally despised components of our flora, even though they play an important part in supporting pollinators and other animals. These brambles’ customers in turn may depend on secretive moths for the sexual reproduction of their hosts. As is often the case in nature, the plot is considerably thicker than it looks.

Among the brambles, by Valentine Cameron Prinsep (1838–1904), enjoying luscious berries © Stephen Craven, Wikimedia Commons.

Pollinators Along the Tweed

Charlotte Rankin is our guest blogger today. Charlotte works as a Conservation Office for Buglife Scotland and leads on the Pollinators Along the Tweed project.

Pollinators Along the Tweed, a new Buglife Scotland partnership project enhancing and restoring 40 hectares of wildflower-rich habitat along the River Tweed, is set to create a buzz for local pollinators and communities.

Learning how to carry out FIT Counts at Traquair bioblitz

Working with Scottish Borders Council, Borders Forest Trust and other landowners in Scotland and north Northumberland, Pollinators Along the Tweed sets to create, enhance and restore 40 hectares of wildflower-rich habitat. Working across 50 sites in towns and villages along the Tweed, as well as the wider countryside, this project will help restore habitat connectivity for pollinating insects, enabling them to move across the landscape and adapt to a changing environment.

Part of the Destination Tweed source-to-sea river revitalisation project, Pollinators Along the Tweed is being made possible with funding from the National Lottery Heritage Fund, AEB Charitable Trust, Craignish Trust, Fallago Environment Fund, J & J R Wilson Trust, Milkywire, NatureScot, Northumbrian Water Group and ScottishPower Foundation.

Boosting early flower resources for pollinators at Tweedsmuir

Running from November 2022 to May 2027, the project will enable communities to learn about, protect and monitor the Tweeds’ pollinators. There will be opportunities to join in practical conservation volunteering, pollinator workshops and walks, citizen science activities and more – from meadow bug hunts to school sessions and wellbeing walks. The project also aims to provide additional support to landowners and managers through habitat management advice and workshops.

Since launching in November 2022, volunteers have been busy bee bank building at Peebles Golf Club, seeding margins of wetland scrapes at Border Forest Trust’s Corehead, and boosting early season flower availability for pollinators at Tweedsmuir and Norham. With the pollinator season getting underway, an events programme is shaping up with opportunities to get involved in pollinator surveying, identification and family activities. So far, children have got involved in crafting hoverfly lagoons and individuals have learnt how to carry out Flower-Insect Timed Counts, with more events on the way – please contact Charlotte.Rankin@buglife.org.uk if you would like to find out more about upcoming events.

Insects recorded at Traquair House bioblitz

Pollinators Along the Tweed further builds on Buglife’s B-Lines and pollinator projects both in Scotland and England. B-Lines present an opportunity to create a network of wildflower-rich areas, providing essential routes for pollinators to use. The B-Lines network includes our best habitats and identifies key areas to restore and create new wildflower-rich meadows, important grassland verges and pollinator friendly gardens. B-Lines can be adopted by farmers and landowners, local authorities and communities. Everyone who manages land can help to restore our pollinator populations.

If your farm, garden, local park or area is within the Tweed B-Line or wider B-Line network and you would like to know more to get involved, please contact Buglife Scotland at scotland@buglife.org.uk. Find out more about the Pollinators Along the Tweed project by visiting buglife.org.uk/projects/pollinators-along-the-tweed.

Building a bee sand bank at Peebles Golf Club with Peebles Golf Club’s Biodiversity and Ecology Group

All images courtesy of Charlotte Rankin

Tiny killer’s gigantic army

By Athayde Tonhasca

The bark louse Echmepteryx hageni (order Psocodea), an obscure fungus-eater from North America, is no more than 10 mm in length. Unsurprisingly, its eggs are miniscule. But these small dollops of nutrients are plenty for the egg parasite Dicopomorpha echmepterygis, a wasp in the family Mymaridae, which are known as fairyflies or fairy wasps. We have little information about this parasitic wasp, but we do know that males are blind, wingless and phoretic, that is, they need to cling to another organism to move about; in this case, females are their ride. Males also have no mouthparts, so they cannot feed.

A bark louse E. hageni; its eggs are parasitized by D. echmepterygis © Katja Schulz, Wikimedia Commons.

If you suspect that a male D. echmepterygis shouldn’t expect a long and prosperous life, you are right. He lives off the nutrients taken as a larva from one of his host’s eggs, and those reserves won’t last long. But that’s of no consequence for the male; his only purpose during his short existence is to impregnate a female, which, conveniently, is his means of transportation. He only needs to crawl to the appropriate spot on her body to do the deed. This lifestyle is by no means unusual; many other parasitic wasps have similar traits. But D. echmepterygis males have a unique claim to fame: they are the smallest adult insects on Earth, measuring 139 µm in length (Mockford, 1997). 

Male D. echmepterygis ventral view (scale line = 50 μm) and head (scale line = 20 μm) © Huber et al., Wikimedia Commons.

To have wings and be able to fly, other fairyflies have to be bigger, but not by much: the winged and marvellously named Tinkerbella nana is 250 µm long. We can have a better appreciation of these fragile fairy creatures by considering the hardships of being small – the risk of desiccation, and barriers unknown to larger animals such as surface tension and fluid viscosity. Michael LaBarbera’s The Biology of B-Movie Monsters is a highly entertaining and illuminating discussion on the physical limitations of body sizes. For a deeper exploration, D’Arcy Thompson’s underappreciated classic On Growth and Form is a tour de force of the physical properties acting on biology.

L: The fairyfly Tinkerbella nana (scale line = 100 μm) © Huber & Noyes, 2013. (CONTENT WARNING to University of Aberdeen’ students: the following refers to J.M. Barrie’s emotionally challenging Peter Pan). The genus Tinkerbella was named after Tinker Bell, while the nana epithet was inspired by the Darlings’ dog Nana – which is also a derivation from nanos, the Greek word for dwarf. R: A micrometre scale for comparing the sizes of D. echmepterygis and T. nana © Zeiss Microscopy, Wikimedia Commons.

There are many fairyflies besides D. echmepterygis and T. nana: over 1,400 of them. And these are the known species; certainly the true number is much higher. All described species are egg parasitoids (their young develop on or inside another organism, eventually killing it) of a range of insects, and they are good at finding their victims: some fairyflies parasitize eggs embedded in plant tissue, buried in the soil and even submerged in water. 

Fairyflies belong to one of the many families of Chalcid wasps or chalcidoids (superfamily Chalcidoidea). This is an enormous group of about 22,500 known species, although the total could reach over 500,000 (Noyes, 2019). Most of them are small (less than 3 mm) parasitoids of different life stages of many insects and arachnids (spiders, mites, scorpions and others).

L: A female Richteria ara justifies the fairyfly epithet. Scale line = 1000 μm (1 mm) © Huber, J.T. R: A much larger chalcidoid: Conura sp. © Judy Gallagher, Wikimedia Commons.

A great number of insects and other arthropods have to live with the high probability of bumping into a chalcidoid wasp, but that’s not the half of their problems. Around 25,000 species of Darwin wasps, or ichneumonids (family Ichneumonidae), and some 17,000 species of braconids (family Braconidae) join forces in a vast army of parasitic wasps – and again, these figures are likely to  grossly underestimate the real number of species. 

As the story goes, J.B.S. Haldane (1892-1964), British/Indian geneticist, evolutionary biologist, mathematician and more, found himself in the company of a group of theologians. On being asked what one could learn about The Creator from studying his creation, the atheist Haldane is said to have answered ‘an inordinate fondness for beetles.’ Haldane may have said something of the sort, and indeed a Celestial Big Cheese would be seen as partial to the order Coleoptera. With nearly 400,000 known species, beetles lead the biodiversity table, comprising about 25% of all animal species (excluding Bacteria and bacteria-like Archaea). But there is strong bias here: beetles are popular and relatively easy to find, while most parasitic wasps are very small, hard to identify, and tricky to handle and preserve in collections. It’s a lot of work, and there are not many specialists in the area. But the more they look for parasitic wasps, the more beetles’ predominance is challenged. Most holometabolous insects (those with four life stages: egg, larva, pupa, and adult) are attacked by one or more hymenopteran parasitoid, sometimes five or even ten, although we may not know their identities. By modelling parasitoid-to-host ratios for some groups of insects, Forbes et al. (2018) estimated that hymenopterans easily beat beetles in the biodiversity league. Some coleopterists may not like to hear that. 

Number of named species as of 2022 © Hannah Ritchie, Our World in Data. ‘To a rough approximation and setting aside vertebrate chauvinism, it can be said that essentially all organisms are insects’ (May, 1988). Parasitic wasps may be greatly responsible for that. 

Parasitic wasps are practically everywhere; just in one suburban garden in Leicester, England, Owen et al. (1991) collected 455 species of Darwin wasps, some new to the British list, in a two-year period. These wasps have an enormous sway in the structure and composition of biological communities. They limit the numbers of insects and spiders, and by keeping herbivores in check, they have an indirect but vital influence on the diversity and abundance of plants. Naturally, pollinators are not immune. It goes without saying that the nature of our flower-visiting assemblages is shaped by parasitic wasps.

Trioxys complanatus ovipositing into the body of a spotted alfalfa aphid (Therioaphis maculata) © CSIRO, Wikimedia Commons. ‘Insects…in all likelihood exert a greater impact on terrestrial ecosystems than any other type of animal. They are the glue holding an ecosystem together: in their millions they consume plants, and in their millions they are consumed by other organisms’ (LaSalle & Gauld, 1991). And in their millions they are killed by parasitoids.

We can gauge the regulatory power of parasitic wasps by their efficacy as commercial biological control agents. For example, Encarsia formosa is one of the most efficient weapons against whiteflies in glasshouses, while Anagyrus lopezi saved cassava crops from the ravages of mealybugs in Africa and Asia. 

L: Cards containing E. formosa eggs to be placed in glasshouses © Dekayem. R: A. lopezi, a scourge of mealybugs © CIAT, Wikimedia Commons.

LaSalle & Gauld (1993) estimated that at least 50% of the 150,000 or so species of Hymenoptera are parasitoids. They all have the alarming habit of eating their hosts from inside their innards while they’re still alive, which seems execrable and cruel. Darwin was dismayed by it, as he expressed in a letter to his friend Asa Gray in 1860: 

‘I am bewildered.— I had no intention to write atheistically. But I own that I cannot see, as plainly as others do, & as I sh^d wish to do, evidence of design & beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidæ with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.’ 

Despite Darwin’s misgivings, parasitic wasps are not particularly shocking, considering that approximately 40% of all known species are parasitic (Dobson et al., 2008). And these tiny, fragile agents of doom are just a fraction of many others such as viruses, fungi, protozoa and worms, who have an array of imaginative ways to cause sickness, suffering and ghastly deaths. Haldane’s god, so fond of beetles, also has a kinky sense of humour.

Relative abundance of different taxa, and the proportion of parasitic species in those taxa. The area of a circle corresponds to the natural log of the total number of species in a taxon © Dobson et al., 2008.

But such anthropomorphic considerations are misguided. Parasitoids, parasites and predators are regulators of the natural world. They prevent excessive population growth, including of agricultural pests and disease vectors, and remove the old and sick from the general population. Parasitism helps shape biodiversity and ecosystems, so it is not intrinsically bad or good. It is a characteristic of life on our planet. It is as it is. 

‘Morality is a subject for philosophers, theologians, students of the humanities, indeed for all thinking people. The answers will not be read passively from nature; they do not, and cannot, arise from the data of science. The factual state of the world does not teach us how we, with our powers for good and evil, should alter or preserve it in the most ethical manner’ (Gould, 1982).

‘We entomologists, who have no charismatic elephants to hide behind, no cuddly panda bears to hug before the public, no aesthetic whooping cranes, no passion-inducing spotted owls, no thousand-year old forest giants – we entomologists are at the forefront of the biodiversity battle with only our bugs for a shield’ (Grissell, 1999). 

Benign delinquents

By Athayde Tonhasca

Christian Konrad Sprengel (1750-1816) is not widely known nowadays, but the German teacher, naturalist and theologian was a pioneer in recognising flowers as lures to insects. Sprengel made significant contributions to our understanding of the role played by insects in plant fertilization, although his writings, published in German, were mostly ignored outside Germany (which is a common fate in the Anglo-centric scientific world). Even still, Sprengel’s discoveries were acknowledged by Darwin in his own work with plants.

A page of Sprengel’s Das entdeckte Geheimniss der Natur im Bau und in der Befruchtung der Blumen (‘The secret of nature discovered in the structure and pollination of flowers’), 1793 © Uwe Thobae, Wikimedia Commons.

Among many novel contributions, Sprengel recorded the ‘outrage against a flower’ played by some bumble bees; they perforate the base of a flower to get access to its nectar, bypassing its opening. From the plant’s perspective, this is cheating. A bee that avoids the flower’s reproductive parts may not pollinate it: the metabolically expensive nectar could be for nothing. This behaviour is known as nectar robbery, a term that reflects a sympathetic bias towards plants; after all, bees – and other insects and some birds as well – are just getting a resource that would be inaccessible otherwise. Most robbed flowers have tubular corollas or nectar spurs (hollow extensions that contains nectar-producing organs) which are out of reach for many visitors, especially bees with short tongues. You can watch them in the act here.

Nectar spurs on Aquilegia formosa; not reachable by traditional means © Daniel Schwen, Wikimedia Commons.

It has been long assumed, reasonably, that primary nectar robbers (those that perforate the flower to access nectar) and secondary nectar robbers (species that take advantage of existing perforations), are bad: ‘all plants must suffer in some degree when bees obtain their nectar in a felonious manner by biting holes through the corolla’ (Darwin, 1872). Indeed, robbers may reduce the availability of nectar to conventional flower visitors, therefore affecting plants’ reproductive success. Robbers may also destroy floral structures while in the act of breaking in.

A buff-tailed bumble bee (Bombus terrestris) pilfering nectar © Alvesgaspar, Wikimedia Commons.

In Brazil’s Atlantic Forest, the understory shrub Besleria longimucronata is pollinated by the reddish hermit (Phaethornis ruber) and violet-capped woodnymph (Thalurania glaucopis) hummingbirds – that is, if the stingless bee Trigona spinipes is not around. Despite lacking a sting, this bee is quite aggressive, pursuing and biting intruders with its sharp teeth, so that it can perforate the flowers and take their nectar at leisure. Those hummingbirds that are not driven away avoid the nectar-depleted flowers; even worse for the plant, some hummingbird individuals slip into a criminal life themselves and become secondary robbers, taking advantage of the holes created by the bees. As a consequence of the robber’s direct and indirect actions, the shrub suffers a reduction in seed production (Bergamo & Sazima, 2018). Trigona spp. are notorious nectar rustlers throughout the Neotropical region, damaging many wild plants and crops in varying degrees. 

A Besleria sp. shrub (art by Louis van Houtte), its violet-capped woodnymph pollinator (©
Dario Sanches), and the nectar robber T. spinipes (© José Reynaldo da Fonseca), Wikimedia Commons.

But as is invariably the case in biology, things are more nuanced. Bees tend to stick around patches of rewarding flowers to save energy and forage more efficiently. But if flowers are low in nectar because of robbing, bees are forced to fly longer distances to get what they need. Also, they often spend less time in a given flower and visit more flowers per unit of time to compensate for lower nectar volume. All this shuffling about has a positive outcome for plants: more flowers are visited, more pollen is deposited on stigmas, and outcrossing (mating of unrelated individuals) is more frequent: the end result is increased reproduction and fitness. 

Some of these effects were elegantly demonstrated by Mayer et al. (2014) in experiments with potted aconite or monkshood (Aconitum napellus lusitanicum). This endangered herb is pollinated by the common carder bee (Bombus pascuorum), and often robbed by the European honey bee (Apis mellifera). The researchers simulated nectar robbing by removing nectaries from some flowers and estimated pollen dispersal by dabbing anthers with fluorescent dye, a pollen surrogate, which was subsequently detected in stigmas collected from plants placed at some distance from the source. The results: bumble bees visited fewer flowers per plant and spent less time per flower. Also, fluorescent dye from patches with robbed flowers was dispersed over larger distances when compared to dye from control plants that had not been artificially robbed. 

A bumble bee making way among the petals of an aconite to get access to its nectar © Franz van Duns, Wikimedia Commons.

And robbers often do more than rob. In northwest Spain, the hairy-footed flower bee (Anthophora plumipes) is the main pollinator of kidney vetch (Anthyllis vulneraria vulgaris), but muggers interfere in this relationship: the buff-tailed (B. terrestris) and the heath (B. jonellus) bumble bees may purloin over 3/4 of all kidney vetch flowers. Despite this rampage, robbed flowers have a higher probability of setting fruit than intact flowers. It turns out that robbers are forced to trample all over the plant’s capitulum (an inflorescence of closely packed flowers), touching anthers and stigmas during the act of thievery, pollinating the flowers (Navarro, 2000).  

The heath bumble bee, a nectar robber, stomps around a kidney vetch capitulum, pollinating the flowers © Arnstein Staverløkk and Ivar Leidus, respectively. Wikimedia Commons.

Other studies have confirmed the pollination role of nectar robbers, such as the case of the fuzzy-horned (B. mixtus) and frigid (B. frigidus) bumble bees when visiting tall bluebells (Mertensia paniculata) in Alaska. These two bees pollinate flowers during their early stages of development, when pollen is plentiful, but shift to nectar robbing when nectar becomes abundant later on. But this is not only about a change of diet preferences: older flowers to be robbed of their nectar attract pollinators to young flowers nearby, which means that nectar pilfering aids the pollination of tall bluebells (Morris, 1996).

Tall bluebell flowers are pollinated then robbed, with a positive outcome for the plant © Walter Siegmund, Wikimedia Commons.

Sprengel labelled nectar robbing an ‘outrage against a flower’ and Darwin considered it ‘a felony’, but there’s more to it than meets the eye. Thorough investigations have shown that in some cases flower larceny reduces plant reproduction and fitness, but there are many instances of no ill effects on plants, or even beneficial outcomes. It all depends on flower and robber morphologies, insect behaviour, flower density, how much nectar is available, how much of it is taken away, and so on. 

‘Robbery’ sounds like a wrench thrown in the mutualistic relationship between plants and pollinators, but the phenomenon is way too common and widespread to be considered an anomaly. And like many other natural events, first impressions can be deceiving: the sight of a flower damaged by a rough visitor is not necessarily a harbinger of harm. 

Flowers with punctured corollas, indicating nectar robbing. This could be bad, neutral or good for the plant © Raju Kasambe, Wikimedia Commons.

Just the ticket

In 2018 it was reckoned that transport accounted for 25% of greenhouse gas emissions across the European Union. That’s a big environmental footprint, and explains why developments such as electrification of rail systems gather momentum. Rail travel remains one of the few areas of travel that governments seem confident in encouraging. It is, after all, the least impactful mass travel mode out with walking and cycling. 

Nicole Tyson, Sustainability Manager at ScotRail, is increasingly on track when it comes to identifying opportunities to help nature – especially pollinators – around our rail network. She oversees the roll out of a suite of projects across Scotland intended to boost nature whilst making travelling by train a more pleasant experience. 

“We have impressive projects at Gartcosh, Kilpatrick and Dalry, for example, where station adopters have developed wildflower areas adjacent to the stations,” she notes. “We also have ongoing projects, with our partners The Conservation Volunteers, at our Yoker and Shields Depots, where we have reduced mowing and introduced wildflower areas, installed bug hotels, and created heritage variety orchards.” 

We recently met with Nicole to discuss Scotland’s Pollinator Strategy and to identify areas where we could collaborate further to effectively deliver positive results for pollinators. One outcome is that we will look to enhance their work with station adopters on a practical level by providing pollinator seed packs and information signs to help transform pockets of land next to stations.  

Nicole is particularly fulsome in her praise of ScotRail’s long-term partners – The Conservation Volunteers. “It’s great to see our partnership biodiversity improvement programme continue to flourish,” she explains. “These projects help more than just the environment as by volunteering outdoors, it also enhances individual mental wellbeing through increased contact with nature and connecting with other people. There are clear social benefits through group activity, which helps people contribute something positive to their community. 

“We recognise the part we have to play meeting Scotland’s ambition to be a world leader on tackling climate change, and we’re fully committed to creating a sustainable railway and which contributes to an environmentally aware Scotland.” 

The train operator currently has more than 250 stations and over 1,000 volunteers across the country enrolled in its impressive Adopt-a-Station volunteering programme. From Dyce to Dalry volunteer groups work to improve the physical environment of their local station which includes activities such as installing planters, station gardens, and information boards.  

The successful work around the depots at Yoker and Shields has been replicated to transform Bathgate and Haymarket depots. Again a mix of tactics have been employed, from wildflower spaces, orchards, and bug hotels to increasingly popular reduced mowing regimes. These changes can have surprising impacts, such as field voles exploiting the relaxed mowing in one location by quickly inhabiting several embankments. 

Recently ScotRail has invested £40,000 annually in their biodiversity improvement programme, supporting more than 50 projects. In enhancing habitats for foraging insects and creating nine wildflower meadows they have made a telling impact for pollinators.  

It isn’t just the insects which have benefited from ScotRail’s confident approach. It has introduced almost 190 volunteers in local communities to valuable new environmental skills. Staff too increasingly relish the benefits of having improved access to wildlife-friendly spaces on their doorstep at depots.  

Nicole sums things up nicely when she says that “We believe that there is a place for nature in all our towns, cities, and local communities. This includes in and around the railway too. Our stations and depots are all key places that can support biodiversity efforts. That’s why you’ll find floral displays at stations across the country to encourage wildlife, and wildflower meadows, ponds and orchards planted across our depots.” 

We sometimes have a blind spot when it comes to considering transport corridors and their value to pollinators. Thank goodness that people like Nicole have rail network opportunities firmly in their sights. 

Further reading

NatureScot have an online leaflet detailing some of the opportunities our transport corridors offer for pollinators.

Undesirables in your garden

By Athayde Tonhasca

The Greek philosopher Theophrastus (c. 371 – c. 287 BC) dabbled expertly in sundry areas, from biology to physics, ethics, metaphysics, mineralogy, and languages. But he’s best known today for his contributions to botany: thanks to his two surviving botanical treatises, Theophrastus was titled ‘the father of botany’ by Carl Linnaeus. 

Among many observations about the plant world, Theophrastus recognised something unusual about some roses (Rosa spp.): their flowers had an anomalous number of petals. Theophrastus had no way to know that these atypical flowers are the result of mutations; cells that were supposed to become reproductive parts develop instead into extra petals. In the botanical world, these flowers with additional petals are known as double-flowered.

A wild R. rubiginosa and a double-flowered cultivar of R. chinensis © Stan Shebs and Sakurai Midori, respectively. Wikimedia Commons.

Since ancient times, the double-flowers’ showy, intricate blooms with densely packed petals have sparked the interest of plant lovers and plant breeders. They have been keeping and propagating spontaneous double-flowered forms of roses and other garden plants such as camellias (Camellia spp.) and carnation (Dianthus caryophyllus). Double-flowered varieties, which are identified by their scientific names followed by the abbreviation fl. pl. (from the Latin flore pleno, meaning ‘full flower’), have inundated the market of ornamental plants. Nowadays most cultivated rose varieties are double-flowered, and some of them have up to 40 petals. Because of their aesthetic properties, double-flowers are widely used in hanging baskets, urban flower beds and public gardens.

Cultivated roses originated from two main regions of domestication: Europe/Middle-East and China. Double-flowers were selected independently in the European and Chinese lineages © Dubois et al., 2010.

Plant breeding is a lucrative and sophisticated activity. Flower producers can attend to an array of consumers’ demands such as plant size, uniformity, flower durability, shapes, colours, and the all-time favourite, flamboyant flowers. The artificial selection of characteristics for our convenience and aesthetic preferences may please some gardeners and urban planners, but they do not please one interest group: pollinators. Because all or a large portion of their reproductive structures have been turned into petals, many double-flowered plants have little or no pollen – a favourable aspect in one regard: they don’t trigger allergies.  Carpels (the female parts of a flower) and anthers (the pollen-bearing structures) are found underneath the petals of some varieties, but they are few and hard to get at. So some double-flowered plants are fertile, but produce a small number of seeds; some can’t reproduce at all, and have to be propagated through cuttings. And there are more bad marks for double-flowers. Their extra petals prevent or obstruct access to the nectaries, which usually are at the base of the petals. So insects don’t bother with these plants, or even worse: they may bother. Many double-flowers produce scents just like their wild counterparts, attracting visitors that go away empty-handed after wasting time and energy.

A bee with full access to a wild rose © Debivort, Wikimedia Commons.

If you want to do your bit for pollinators in your garden or allotment, you don’t need to ban double-flowered varieties altogether, but do give preference to the old-fashioned single-flowered geraniums (Geranium spp.), petunias (Petunia spp.) and fuchsias (Fuchsia spp.), and other pollinators’ favourites such as snapdragons (Antirrhinum spp.), borage (Borago officinalis), crocuses (Crocus spp.) and hollyhocks (Alcea spp.). There are many options of colours, growing habits, sizes, time of flowering, etc., to make a garden beautiful, diverse and attractive to wildlife. 

You may be willing to accommodate plants that will not help you win a gardening prize, and may even provoke a raised eyebrow from a neighbour. Plants like the smooth hawk’s beard (Crepis capillaris) and wild mustard (Sinapis arvensis) are unassuming and often undesirable, but they are very good in attracting solitary bees (Nichols et al., 2019). If there’s a hedge or wall in your garden, you couldn’t have a better choice than the dog rose (Rosa canina), a climbing plant that is another excellent source of pollen for mason (Osmia spp.) and leafcutter (Megachile spp.) bees (Gresty et al., 2018).

Smooth hawk’s beard (L) and wild mustard, good sources of pollen © Michael Becker and Hectonichus, respectively. Wikimedia Commons.

And as a bonus to laidback gardeners, some plants like the lesser calamint (Clinopodium nepeta), and the autumn sneezeweed (Helenium autumnale) attract a wide range of insects and require little or no maintenance: just let them grow. A similar attitude towards unwanted species such as bramble (Rubus fruticosus) buttercups (Ranunculus spp.) and dandelion (Taraxacum officinale agg.) would be another boost to pollinators, as these plants are also outstanding providers of pollen or nectar (Lowe et al., 2022). You don’t need to let them take over, just show some tolerance to these humble garden companions.  

A dog rose (© H. Zell), a great source of pollen for the red mason bee (O. bicornis), top right (© bemma) and the patchwork leafcutter bee (M. centuncularis) (© James K. Lindsey), Wikimedia Commons. 

Close to 7% of the UK land area is classified as urban, home to about 80% of the population (Davies et al., 2009). Around 87% of UK households have access to a domestic garden (Gibbons et al., 2014). If all these city people have pollinators in their minds when designing their gardens and choosing their plants, the benefits to nature, pollinators and ultimately to ourselves would be huge. Avoiding gaudy, artificial-looking flowers would be a good start.

Beauty and food for pollinators from simple flowers © Alvesgaspar, Wikimedia Commons.

A flag and a sword

The Flag Iris is a hard plant to ignore. Tall, imposing and colourful. References to it abound in Scottish literature, one of the simplest, and perhaps my favourite, belongs to Norman Collie, the famous climber, who noted in a 1932 Cairngorm Club Journal, with more than a hint of admiration, that the ’The tall iris nods slowly in the wind’.

It’s a hard plant to overlook.  Flowering may be short-lived, and falls between late spring and early summer, but the plant structure remains visible in right through until October. The Flag Iris, Iris pseudacorus, is often found in damp, boggy locations and then frequently in clumps. It’s a popular plant with pollinators, and as the flowers are often at eye level a good choice for some pollinator watching.

The bold yellow flower is certainly distinctive. Large and flimsy it gives the plant its common ‘flag’ name. It was a staple of the Scottish clothing industry in the 18th century – used as a dye. The roots were used in the colouring of tartan and tweed, mixed with other elements to achieve dark colours, whilst the sword-shaped leaves helped create green dyes.  In days gone by in parts of Tiree the broad leaves of the Iris were often used in roof thatch.

It still helps offer a home today, to the elusive corncrake no less, which is quite happy to skulk in the deep cover it provides.

Of course you will expect this common plant to have a medicinal use too, and you wouldn’t be disappointed. The roots were dried and crushed before being used to tackle a range of ailments including toothache, headaches and colds. In some places the roots were also employed as a laxative. That is unlikely to have been any more pleasant than the anecdote a colleague shared with me about how the rhizomes were crushed and the resulting liquid poured or inhaled through each nostril as a treatment for toothache.

Delve deeper and you find that the Yellow Flag was once a heraldic symbol. The fleur-de-lis, adorned the symbols of the French monarchy and in Scotland was included in the Royal Arms of Scotland. Going further back and into the world of Greek myths Iris was revered as a messenger of the gods, and credited with steering the departed souls of women to the land of Eternal Peace. Hence Iris were, in some parts, planted near graves.

The sword-like leaves have, not surprisingly, been behind several of the ancient names for the Flag Iris.  Water Skegg, Jacob’s Sword, Swordgrass, and Daggers all reflected the shape of the leaves. Yellow Flag and Sword Flag derived their name from the fluttering of the yellow petals. Surprisingly, the bulbous green seedpods of our native Iris don’t appear to have spawned any peculiar names.

There has been a British Iris Society since 1922, devoted diligently to the cultivation of this striking plant. Indeed there are Iris societies across the globe. They will confirm that the element of the name pseudacorus literally means ‘false acorus’. The pseudo element stems from the Greek word meaning ‘false’, and acorus, indicates that the plant it isn’t is the Sweet Flag plant; all of which I suspect tells us that this plant was once labelled as an imposter.

When it comes to Flag Iris pollinators – there are many. It is easy to observe both flies and bees, especially bumblebees, visiting this flower. Most pollinators land on the lower outer petals and thereafter they quickly become dusted in pollen as they slip past the three smaller inner petals and dip into the flower head. Suitably dusted, the thorax will brush against the stigma in the next flower visitation and the job is done.

Blood, toil, tears and sweat

By Athayde Tonhasca

The Paraguayan War (1864-1870), waged by Paraguay against Argentina, Brazil and Uruguay, has a special place in mankind’s history of cruelty, carnage and devastation. Among the many horrors witnessed by combatants and observers, the episode described by Lieutenant Alfredo d’Escragnolle Taunay is particularly odd and gruesome: “Another plague persecuted them [horses, mules and asses] relentlessly, and this singular one had disastrous effects. It came from some extremely beautiful butterflies, the so-called 88, as they appear to have that number written on the outside of their brindled wings with whimsical black-and-white drawings. However, one cannot imagine the actions of those gentle Lepidoptera, in appearance quite innocent, but in fact extremely pernicious, in all that part of Paraguay. They would huddle together in the corners of the eyes and in the nostrils of the animals, seeking any bodily moisture and soon causing such irritation at the spots where they stubbornly landed, and it did not take long to produce abundant discharge, at first of mucous and soon after copious pus! A horror! What despair from our unfortunate mounts struggling to defend themselves from the immense, flagellating legions of tiny enemies, ever more numerous and ferocious! What continuous and tiresome weaving! Unable to graze, they grew thin under our eyes and soon were completely blinded! Once on the ground, surrounded by thousands of assailants, each eye socket became a hideous and disgusting source of purulent rivers, which attracted even more the terrible butterflies. We would have surely lost all our beasts of burden and mounts, if adequate measures had not been taken, by providing them with a headband of maize straw cut into fine threads, which served as a shield to the eyes without obstructing their view.” (Taunay, 1874. Recordações de guerra e de viagem).

Caught in the maelstrom: during the Paraguayan war, horses would succumb to wounds, hunger, exhaustion, cold, and butterflies. Art by Pedro Américo (1843-1905), Wikimedia Commons.

This butterfly worthy of a Stephen King novel is the Cramer’s eighty-eight (Diaethria candrena), which ranges from eastern Paraguay to southwestern Brazil, northern Argentina, and Uruguay. Adults are often seen in orchards, as they feed on rotting fruit. They also concentrate at the edge of ponds and puddles, on spots covered by ash after fires, and in bare soil soaked with livestock urine. This gathering behaviour was known by Tupi-Guarani speakers as panapaná, ‘a gang of butterflies’. For Anglophones, these butterflies are ‘mud-puddling’.

A Cramer’s eighty-eight ventral and dorsal view © Fernanda Hisi and Geoff Gallice, respectively. Wikimedia Commons.

Butterflies mud-puddle supposedly – data are scarce – to collect salts, especially sodium. This chemical element is one of the most abundant in the Earth’s crust but occurs in minute quantities in plants because they don’t need much of it. That’s a problem for plant feeders, who require sodium in concentrations 100 to 1,000 higher than what they get in their food. Herbivores rely on their metabolism to accumulate sodium, and also on any alternative sources such as mineral licks, which are natural deposits of salts and other minerals: they are found in places such as exposed, muddy areas high in clay and organic matter. Faeces and dead bodies will do as well.

A herd of Indian bison (Bos gaurus) in a salt lick, and butterflies mud-puddling © Amog, and Vinayaraj, respectively. Wikimedia Commons.

Most mud-puddling butterflies are males, so researchers have suggested – again, data are lacking – that nuptial gifts are behind this behaviour. The sodium gathered by males would be passed to females during copulation and then to the offspring, helping them to cope with a sodium-poor diet. But as females of some species mud-puddle as well, there must be more to the story.

Butterflies and other insects visit mineral licks to get their sodium fix, but these deposits may not be enough for their needs. The bodily secretion of some animals – sweat – is an attractive alternative for a bold insect willing to risk being squashed by an angry host in exchange for a lick of salt. Several species in the second largest family of bees, the Halictidae, are known as sweat bees because they use perspiring people as their salt licks. These bees are harmless, but can be quite annoying with their persistent hovering and tickling. 

Besides sweat, tears are an excellent source of salts, a fact enthusiastically exploited by the Cramer’s eighty-eight in Paraguay to the chagrin of poor horses and their minders. And a surprisingly large number of butterflies, bees, flies and other insects drink tears. In addition to horses, these insects take their salty beverage from cattle, sheep, pigs, water buffaloes, antelopes and elephants; birds, crocodiles and turtles are also suitable. In Burma, India, Sri Lanka and Thailand (and probably other countries too), human beings are also involuntary tear donors to at least six species of moths. Besides the ick factor, tear-seeking insects are to be avoided because of the risk of transmission of eye diseases such as the trachoma virus and ‘pink-eye’ (conjunctivitis) in human beings (Bänziger & Büttiker, 1969).

A Lobocraspis griseifusa moth sucking tears © Bänziger & Büttiker, 1969.

As lachryphagy – from the Latin lacrima (tear) and the Greek phagos (eating, feeding) – is fairly common, Bänziger et al., 1992 proposed that there’s more to it than just sodium taking. Insects may be after amino acids and proteins, which occur in tears in fairly high concentrations. The researchers noted that tear-dinking bees rarely visit flowers or carry pollen, which suggest they may be getting all or most protein they need to raise their young from tears. 

Alas, sweat and tears may not satisfy the mineral/protein needs of some insects. 

Many moths and butterflies feed on extra-floral nectar, sap, or decaying fruit as the Cramer’s eighty-eight does. But some moths in the subfamily Calpinae (family Erebidae) don’t have to sit around waiting for a fruit to break open: they use their stout proboscis, which is armed with hooks and barbs, to pierce the skin of a fruit to feed on its flesh and juices. Some species in the genus Calyptra in Southeast Asia found another use for their tough proboscis: to feed on the fluids exuded by cuts, sores, scratches, scabs, and other open wounds of animals. 

Distal region of the proboscis of Gonodonta bidens, a fruit-piercing moth. Lgl are legulae (rasping spines), and th are tearing hooks © Zenker et al., 2010. Journal of Insect Science 11:42 insectscience.org.

It takes a small step to go from exploring a host’s skin for an open wound to piercing it to get access to the richest bodily fluid of all – blood. Some Calyptra species have developed the ability to puncture the skin of cattle, pigs, mules, deer, antelopes, water buffaloes, elephants and rhinoceros. If these moths can pierce rhinoceros skin, they would have no difficulties with a hairless, thin-skinned primate: at least five Calyptra moths are known to feed on humans. Predictably, they are known as vampire moths.

If you want to place blood-sipping moths in the list of bizarre creatures from faraway tropical countries, think again. The vampire moth Calyptra thalictri, originally from Asia and Eastern Russia, has slowly expanded its range to northern Europe, being observed in Finland and Sweden. Watch C. thalictri having a vampirism moment, but nobody should lose sleep over it: human blood feeding by moths is harmless and extremely rare. Calyptra spp. diet comprises mostly soft-skin fruits (raspberry is a favourite), which they puncture to reach the sugar-rich juices.

Calyptra thalictri © Ilia Ustyantsev, Wikimedia Commons.

Approximately 14,000 insect species are hematophagous, that is, they feed on animal blood. Most of them are obligatory hematophagous: they need blood as a source of nutrients and cannot survive on any other food. Some butterflies and moths on the other hand are facultative hematophagous: blood is not vital for them, but increases their chances of survival. In the case of vampire moths, only males feed on blood. So just like for mud-puddling butterflies, male moths apparently are after sodium as a nuptial gift, which they would pass to females during mating.

An obligatory hematophagous specimen. From Archive of Dracula (1931), Wikimedia Commons.

The sodium-gathering hypothesis suggests that mud-puddling, sweat-licking, tear-drinking and blood-sucking are related behaviours. It is also notable that one morphological adaptation, i.e., a sturdy and barbed proboscis, allowed some moths to evolve from nectar-sipping to fruit- and skin-stabbing. Calpinae moths offer another example of insects’ spectacular capacity to adapt and make use of whatever nature has to offer.  

Incidentally, in case you are pondering whether lieutenant Taunay – later a Viscount – exaggerated or made up his butterfly story (porkies are not unheard of in war memoirs), a similar albeit less dramatic episode was witnessed about half a century later in the vicinity of Iguazu Falls, not too far from the Paraguayan killing fields. ‘Volunteer’ horses had their eyes mobbed at night by no less than eleven species of moths (Shannon, 1928. Science 68: 461-462).

So, are equines at risk from Lepidoptera attacks in central South America? They are not. All the countries involved changed beyond recognition since the war: much of their natural habitats have been converted to soybean fields, pasture and logging wasteland. Numbers of butterflies, moths and just about any other wild animal have plunged, some to the point of near extinction. In these inhospitable environments, the Cramer’s eighty-eight could never reach the Biblical numbers of the past, to the relief of local livestock. You may think of it as silver lining of sorts.

An eighty-eight butterfly, no longer pestering horses. In the background, the Iguazu Falls © Leoadec, Wikimedia Commons.