No pasarán

By Athayde Tonhasca

Between 150 and 200 million years ago, some ancestors of today’s wasps (order Hymenoptera) experienced a momentous transformation. The females’ ovipositor – the egg-laying apparatus – evolved into a stinger that produces a cocktail of chemicals capable of paralysing or killing prey and enemies; egg-laying was moved to an opening at the base of the stinger (you can learn details of this evolutionary tale here). By weaponising their ovipositors, those primitive wasps gained a tremendous boost; they could hunt, forage and defend themselves much more efficiently. The venom-injecting lineage flourished, and today comprises over 70,000 species of ants, bees, and stinging wasps known collectively as the Aculeata (derived from the Latin aculeus, meaning barb, thorn). Some of the most successful organisms on Earth are aculates; ants are the main movers and shakers in almost every terrestrial ecosystem (Hölldobler & Wilson, 1990), while bees are the most important pollinators of flowering plants.

A wasp stinger, with a droplet of venom on its tip. The oviduct that carries eggs to the outside is at the base of the stinger © Pollinator, Wikimedia Commons.

Many people’s attitude towards honey bees (Apis spp.) and social wasps such as hornets (Vespa spp.) is of wariness, if not downright hostility, because of their stingers. But these weapons, despite being unpleasantly effective and potentially dangerous to people and animals, are rarely deployed when bees and wasps are flying about. Most stings happen when these insects are handled, or unintentionally squeezed or trapped. Otherwise, they carry on with their busy lives, ignoring us. 

The venom system of the violet carpenter bee (Xylocopa violacea) © von Reumont et al., 2022. 

The mood changes, though, when they feel their homes are being threatened by a raider. The nest is their main reason for being: it harbours the reproductive queens, their young, and food stores. If its walls are breached, in no time the nest would be overcome by parasites, predators and usurpers, and that would be the colony’s demise. So bees and wasps rely on their stingers to fend off enemies, and few wannabe looters can endure the onslaught of hundreds of tiny, poisonous flying daggers.     

Animals tend to keep their distance from the honey bee’s stinger, a sharp, barbed stiletto loaded with venom. L: a beehive fence to keep elephants from farms in Kenya © Kengee8. R: some creatures put up with bees’ wrath for the nutritional rewards of their nests. Art by Ernest Howard Shepard, 1926. Wikimedia Commons.

Despite its efficacy as a defensive mechanism, the stinger is used sparingly. Animal venoms are protein-rich, complex chemical mixtures and therefore metabolically expensive. So bees, wasps and other aculeates can’t afford to go stinging willy-nilly. Some bees reduce the need to sting by making their homes hard to find. You may watch bumble bees (Bombusspp.) time after time in a garden or local park and never find their nests. Other bees use the same tactic of discreet living for protection.

Living inconspicuously for safety. L: a common entrance to several nests of the chocolate mining bee (Andrena scotica) in a busy street. R: nest of Scaura latitarsis inside a termite mound at the top of a tree, 5 m above the ground; A: diagram of the nest; B: entrance; C: detail of the entrance gallery; En – entry; Tm – termite mound; Gl – entrance gallery; Fc – brood combs; En – honey and pollen pots © Camargo, 1970.  

Possessing a stinger sounds like an essential feature for social bees, but a whole group of them do without one: the stingless bees, or meliponines (tribe Meliponini). Stingless bees comprise over 600 species spread around tropical and subtropical regions of the world, but mostly in South America. They have vestigial stingers, so are unable to sting. You may think the lack of a functional stinger makes them defenceless and vulnerable: you would be wrong. 

Some species resort to simplified but no less effective stinger substitutes. The tataíra (Oxytrigona tataira) from South America and similar species secrete large quantities of highly caustic formic acid from their cephalic glands, which is excruciatingly efficient in discouraging enemies, man or beast. The defensive power of O. tataira, named after the Tupi-Guarani tata (fire) and ire (bee), explains its alternatives epithets of cospe-fogo (fire spitter) and the charming caga-fogo(you will need to look up this one). 

An innocent-looking tataíra © Clara Matos, and the consequences to an obstinate man on a mission to destroy a tataíra nest in his small holding, only to be mobbed by angry bees. Two painful weeks later, the man was back on his feet and wiser © Morais et al., 2020.

Other stingless bees deploy less hurtful weapons (at least to us). The sugarbag bee (Tetragonula carbonaria), an endemic Australian species, defeats invading small hive beetles (Aethina tumida) by mummifying them alive. This beetle, a serious pests of the European honey bee (A. mellifera) in some countries, adopts a ‘turtle posture’ to protect itself from bites and stings once inside a bee nest. But the beetle is being too clever by half; the sugarbag bee coats and immobilises the invader with a gloopy mixture of resin, wax and mud. This pharaoh’s approach (Greco et al., 2010) is known as social encapsulation, and it’s practiced by other bees.

A sugarbag bee © James Niland, and a small hive beetle © James D. Ellis, University of Florida, Bugwood.org, Wikimedia Commons.

To survive, insects have to defend themselves against the many dangers in the big wide world. They may run or fly away, hide, or escape detection by crypsis (blending in with the surroundings). But for many bees, wasps, ants and other insects that live in colonies, there is no other option but to stand their ground and fight back – which they do superbly with chemical weapons. Even though, some social bees do very well with no stings or venom. Like The Perils of Pauline, to be continued…

The Perils of Pauline, 1914. Art by unknown author, Wikimedia Commons.

A feathery pollinator

By Athayde Tonhasca

As gardeners across the country gradually come out of hibernation to resume tending their flower pots and vegetable beds, they can count on one visitor for company: the Eurasian blue tit (Cyanistes caeruleus). This little bird is a common sight all year round in gardens across the UK, and it is definitely good company because it spends a good chunk of its time hunting leaf-munching caterpillars – although flies, aphids, beetles, wasps and spiders would also do for lunch. Outside the breeding season, they also eat seeds and buds.

The Eurasian blue tit © Francis Franklin, Wikipedia Creative Commons

This everyday bird and the related great tit (Parus major) came into the spotlight in 1921 when they were found to be behind cases of pilfering from British residences. These birds had learnt to prise open or pierce the foil tops of milk bottles left at people’s doorsteps to get at the layer of cream underneath. And they became really good at it: “The bottles are usually attacked within a few minutes of being left at the door. There are even several reports of parties of tits following the milkman’s cart down the street and removing the tops from bottles in the cart whilst the milkman is delivering milk to the houses.” (Fisher & Hinde 1949, The opening of milk bottles by birds. British Birds 42: 347-357). The technique spread quickly, and by 1947 several places across the UK were recording bottle-opening tits. The birds’ cleverness became a case study in social learning.

Tits having their breakfast © Fisher & Hinde, 1949. British Birds 42: 347-357

The blue tit is also known for its acrobatics: when searching for food, it can cling to walls, hold on to the narrowest twig and hang upside down to explore holes and crevices. The talent for gymnastics offered the blue tit a new opportunity – a boost of energy from flowers of the crown imperial fritillary (Fritillaria imperialis).

This plant from the lily family (Liliaceae) is native to Asia and valued by European and American gardeners for its clusters of bell-shaped flowers. In the UK, these flowers are visited by bumble bees, which are attracted by abundant nectar. Birds may be enticed as well, although most of them have to cut through the top of the flowers to get to the nectar. But not the blue tit: it has the right size and skill to access the flower through its opening, without damaging it.

Crown imperial fritillary or Kaiser’s crown © James Steakley, Wikipedia Creative Commons

Nectar feeding is rare among European birds: in fact, not one species is considered to be a specialised nectarivore. But the blue tit is known for dabbling in nectar now and then from plants like gooseberry (Ribes uva-crispa) and willows (Salix spp.). Different from most passerine birds, blue tits seem to be able to digest sucrose, a quirk that is likely to give them an advantage over great tits, their garden competitors. 

To the crown imperial fritillary, visits by inquisitive blue tits are most welcome. While probing a flower for nectar, the bird touches anthers and stigma, and when it hops to another flower, inevitably pollen is transferred. So, as a first for a plant growing in Europe, the crown imperial fritillary is mainly – or perhaps solely – pollinated by a bird. 

Blue tits visiting crown imperial flowers © Búrquez, 1989. Oikos 55: 335-340

In Europe, 46 or so bird species visit flowers, and it is usually assumed they are looking for insects or other invertebrates. But most of these birds are generalists, feeding on whatever comes to hand. So it’s possible that some of them occasionally go for a sip of nectar, just like the blue tit. And just like the blue tit, a few birds may contribute to pollination. Of the nearly 100 European plants visited by birds, about a third are introduced species like the crown imperial fritillary. If some of them are pollinated by native birds that take advantage of a novel food source, the ecological implications may be profound. We won’t know until the matter is investigated. Who knows, perhaps some bird besides the blue tit will join insects on the list of British pollinators.

Windswept and interesting

Speak to any National Nature Reserve manager in Scotland and one thing is for sure – they will all tell you that their reserve is, whisper it, actually the best in the country.  Now, I’ve no inclination to take sides, and each and every reserve I’ve visited has been fantastic, but I have to concede that there is something about the tremendous variety at St Cyrus NNR that grabs your attention.

Sure it can be a site of blustery winter storms, and the salty winds promise untold harm to your complexion, but when you have long expanses of beach, rolling sand-dunes and a backdrop of towering inland cliffs you know that you are somewhere special, somewhere to be savoured.

Diversity is the name of the game here. Birds, plants, sea life, scents, sights and sounds jockey for position.  If pollinators are on your wish list then a visit in summer is recommended. The place is simply awash with wildflowers and performs sterling service as a haven for insects. 

Reserve manager Therese Alampo won’t disagree. In fact she will regale you with tales of birds, butterflies, moths, sand dunes, seals and flowers until the sun dips behind you. Selling the virtues of the many paths that criss-cross the reserve comes naturally, as does the insistence that one trip is never enough.  She ought really to be selling tickets … the commission would be incredible.

The pollinator trail is well worth sampling. There are currently eight stopping points on a trail that piggy-backs on existing floral trails.  Subjects covered include the tawny mining bee, unkempt corners, the much maligned ragwort, hoverflies, leaf-cutter bees, and valuing our wasps.

There’s a buzz and a hum at St Cyrus. Pollinators feast on the nectar and pollen banquet.  And the fun starts right at the car park, for within yards of leaving you are likely to come across mining bees making good use of the exposed soil around a fence line. Then it is onto a boardwalk that lifts you over what some might call a scruffy area, but others celebrate as a natural oasis.

Before Covid struck the reserve offered a children’s quiz that added a fun sense of purpose to many school outings around the reserve. As Therese explains the information on offer at the reserve is eagerly soaked up, be it in the shape of quizzes or information panels. “Every day we see people stopping to read the information on the short trail” notes Therese, “sometimes simply capturing an audience that may just be on the way to the beach.  I love people’s reactions to the trail and the fascination, particularly to the wasp panel, ‘Really, wasps are useful? I never knew that!’ It’s lovely to provoke that sense of interest.”

Therese isn’t the only enthusiast for the reserve. Noted local photographer, Pauline Smith, has wowed people for several years now with her stunning macro shots of the insect and flower life on the reserve.  Our blog, and indeed the pollinator information panels at St Cyrus, have been lucky to tap into her amazing skills.

Photographer in residence at St Cyrus National Nature Reserve, Pauline not only takes awesome wildlife photos, but enjoys a deep understanding of the reserve’s nature. When not getting up close to insect life she is a scientific copy-editor and that eye for detail serves her extremely well as a photographer.

Wasps, butterflies, solitary bees, caterpillars and bumblebees have all fallen under Pauline’s near forensic gaze. The images she captures show not just the beauty of nature, but the complexity and detail in the structure of so many of our invertebrates. From camouflage to intricate mouth parts, she is capable of shining a light on the minutest detail. That takes well-honed field craft and a connection with nature. 

Pauline has been enjoying the reserve daily since 2017. She first came to St Cyrus NNR to walk her dog, but was immediately hooked by the huge variety of wildlife supported by the reserve. She hones in on the macro world because she is fascinated by those small details, such as the intricacies of a caterpillar’s foot or the impressive moustache of a male mining bee, that can be revealed by a macro lens. 

Her favourite pollinators are solitary bees, with leafcutters and the gold-tailed melitta being particular favourites. Pauline finds the most challenging thing about macro photography to be getting her subjects to stay still long enough to obtain both aesthetically pleasing bug’s-eye-view photographs and photographs showing enough distinguishing features to allow the species to be identified, which is no mean feat (even with detailed photographs) for solitary bees. Pauline’s commitment to never interfere in the behaviour or habitat of her subjects in pursuit of her envisaged photographs makes her exploration of the macro world an immersive experience, as she enjoys so much time simply observing and learning about her subjects while she waits for natural shots of them going about their ‘buzziness’.

St Cyrus became a National Nature Reserve in 1962. The dune grassland, well-drained and nutrient rich, supports over 300 species of plant. Vetches, speedwell, ragwort … the list of pollinator friendly flowers is expansive. Abandoned churches and fishing stations tell the tale of human association with this site and today it is a highly popular visitor destination.

The pollinator trail is designed to help you get the most out of your visit. And as for the pollinators?  Well, they are certainly well catered for and we hope that trail will help raise awareness of not only this range of insects, but what you can do to help them thrive in Scotland.

Find out more about St Cyrus National Nature Reserve

Find out more about the Pollinator Strategy for Scotland

Images 1 and 2 of St Cyrus Panels, images 3 (composite) and 4 by Pauline Smith.

Fig wasps, evolutionary marvels

By Athayde Tonhasca

When people talk about keystone and indicator species, often what they mean is ‘my favourite species’, or ‘the important species I work with’. But one group of organisms truly deserves the label of keystone species: figs. The genus Ficus comprises over 900 species spread throughout the tropical and subtropical regions as shrubs, lianas (woody vines), or trees. Strangler trees – which don’t strangle anything – are one of the best known types of fig plants.

Many fig species produce fruit asynchronously throughout the year, so many animals have a steady supply of abundant and nutritious food. This is especially important during the dry season, when most plants do not fruit. Figs are often preferred even when other fruits are available because they are rich in calcium, a mineral usually in short supply. So figs are essential for a wide range of birds and mammals such as pigeons, toucans, parrots, macaws, bats, peccaries and monkeys. Over 1,200 vertebrate species feed on figs.

The strangler fig Ficus aurea © Forest Starr and Kim Starr, Wikipedia Creative Commons, and the diversity of fig characteristics © Lomáscolo et al. 2010. PNAS 107(33):14668-72

Figs support the diversity and functioning of ecosystems around the world, but they can only do that thanks to some tiny wasps.

Chalcid wasps are an enormous group of insects, estimated to contain over 500,000 species. Most of them are parasitoids of other insects, but a small group belonging to the family Agaonidae has one purpose in life: to get into a fig to reproduce. By engaging in fruit breaking and entering, these wasps, appropriately known as fig wasps, pollinate the fig plant. 

A female fig wasp © Robertawasp, Wikipedia Creative Commons

The mission is made immensely complicated by figs’ morphology. Botanically speaking, a fig is not a fruit but a type of inflorescence known as a syconium (from the Ancient Greek sykon, meaning ‘fig’, which originated ‘sycophant’, or ‘someone who shows a fig’; a term of curious etymology). A syconium is a fleshy, hollow receptacle containing simplified flowers or florets, and each floret will produce a fruit with seeds in it. A fig harbours dozens to thousands of florets and fruits, depending of the species. The crunchy bits of the fig we eat are not seeds but fruits.

Florets need pollination, not an easy proposition when they are bunched up and locked inside a container. So the fig wasp’s first hurdle is to get inside the fig. A female wasp does it through a hole at the bottom of the fig (the ostiole), which loosens when the fig is ready for pollination. 

Longitudinal section of a syconium. The inner wall of the hollow chamber is covered with florets, and the ostiole at the bottom is the door for female wasps © Gubin Olexander, Wikipedia Creative Commons

A receptive fig does not make life much easier for the female wasp. She has to chew her way through, pushing and squeezing, often having her wings and antennae snapped off in the process. She will find a floret, insert her long ovipositor into it and lay an egg. As she’s busy doing that, pollen grains attached to her body get rubbed off onto nearby florets, assuring their pollination. With the job done, the female wasp dies.

The ovules of florets that receive eggs will form galls in which the wasp larvae develop, while pollinated ovules turn into fruit. The adults chew their way out of the galls, males first. Sometimes they help females get out from their own florets and mate with them. Males will then chew a hole through the fig wall to let the females escape. Males stay behind: they couldn’t go anywhere, as they have no eyes and no wings. After an ephemeral life spent entirely inside a fig and marked by moments of glory such as fertilising females and setting them free, males die. 

A male (L) and a female fig wasp recently emerged from their galls. The male is using his mandibles to open a gall containing a female to let her escape and be the first to mate with her © van Noort et al. 2013. African Invertebrates 54(2): 381-400

A female collects pollen grains from intact florets or picks them up by accident before braving the world outside. She will follow the trail of chemicals released by a host plant to find another fig receptive to pollination and start the cycle again. But she must be quick: she has a few hours to three days to live, depending on the species. And to complicate things, not any fig will do. Each species of fig tree is pollinated by one or a few host-specific fig wasps, which is an outstanding case of coevolution. 

The great majority of female wasps don’t make it, but a few do: they catch rides on wind currents above the canopy to find host plants over 10 km away, farther than most pollinators. This is a remarkable achievement for such small, fragile, and short-lived insects. 

You can learn much more about figs and fig wasps at Figweb from Iziko Museums of South Africa.

Perhaps nothing exemplifies better the wonders of fig pollination than the exploits of Ceratosolen arabicus in Namibia. This wasp pollinates the African fig tree (Ficus sycomorus) along the Ugab river in the North Namib desert. This is one of the most inhospitable and remote corners of the planet, famous for its Skeleton Coast, a place of shipwrecks and marooned sailors. African fig trees occur in isolated clumps along the riverbank, but that’s not a barrier for the wasp: it covers average distances of near 90 km and a maximum of 160 km over the desert at night in search of a receptive fig. As the wasp survives for 48 h or less, this quest must be quick and efficient.

Dry Ugab riverbed, Namibia © Theseus, Wikipedia Creative Commons

How do figs and fig wasps relate to us, denizens of fig-less countries? This pollination system has a profound influence on global biodiversity and ecosystem functioning, so it affects us as well, even if indirectly. The story of figs and wasps also illustrates the capabilities, drive and hardiness of minute, easily overlooked insects that are so important for us and nature.

It’s complicated

By Athayde Tonhasca

Himalayan balsam (Impatiens glandulifera) was brought to the British Isles in 1839 as an addition to Kew Gardens’ collection of ornamental plants. As usually happens with introduced species, Himalayan balsam escaped into the wild, causing consternation ever since. It has spread throughout damp woodlands and along rivers, flourishing in thick stands up to 2 metres high that overshadow the local vegetation. This plant does well in a variety of climatic conditions and soil types, and has a tremendous capacity to spread.

So nobody likes Himalayan balsam. Nobody but pollinators.

Himalayan balsam © MurielBendel, Wikipedia Creative Commons

This invasive is a nectar factory. Each flower produces about 0.5 mg of sugar per hour, a rate far higher than any European plant; flowers of most species yield less than 0.1 mg/h. And because the plant flowers late in the season, nectar it available at a time when other sources start to become scarce. So naturally, bumble bees, honey bees and wasps go for it with gusto. And there is something in store for hoverflies as well; they feed on the copious amounts of pollen produced by these flowers. Predictably, the number of bumble bees and other insects increase in areas invaded by Himalayan balsam. 

This abundance of food could have undesirable side effects. Many bees get the proteins, carbohydrates, lipids and amino acids they need from a variety of pollen sources. But thanks to the plentiful and readily available pollen from Himalayan balsam, bees stick to this easy option: in some situations, up to 90% of the pollen collected by honey bees comes from this plant, with unknown consequences to bees’ development and health. The profusion of pollen and nectar could also indirectly harm other plants: if native species receive fewer visitors, their pollination could be compromised. But the evidence for such outcomes is contradictory. Some studies suggest that Himalayan balsam reduces flower visitation and seed production of native plants; others have demonstrated no differences, or a ‘magnet effect’: Himalayan balsam attracted pollinators to itself and to plants nearby. 

A marmalade hoverfly (Episyrphus balteatus) and a common carder bee (Bombus pascuorum), two Himalayan balsam beneficiaries © Charles James Sharp (L) and André Karwath, Wikipedia Creative Commons

Alien species are a hot and controversial topic among conservationists. Some highlight the damage caused by introduced species to the native fauna and flora, habitats, the economy and even human health. But other conservationists point out that alien species may have neutral or positive impacts: that is, they are alien but not necessarily invasive. The invasiveness of Himalayan balsam has been well documented, but there are mitigating factors in its favour: in some situations, this plant had no effect on local species composition, or at worst it only replaced a few ruderal species (plants that colonise areas that have been disturbed). And its presence may check the spread of harmful alternatives such as the giant hogweed (Heracleum mantegazzianum).

Assessing the impact of alien species is important because a great deal of money and resources have been spent on controlling or eradicating them, quite often unsuccessfully. It is usually assumed that invasive plants are bad for pollinators, but there isn’t much evidence to support this assumption. Like many aspects of species’ ecology, data are scarce, results are often contradictory, and generalisations are risky. In summary: it’s complicated.

Insect inspiration

Insects and football don’t often mix. An influx of flies when England met Tunisia in Volgograd during the 2018 World Cup was a rare occasion. It wasn’t warmly welcomed by players or spectators. Two years earlier at Euro 2016, Silver Y moths were clearly visible as Portugal and France contested the final. But there are a few insects embedded in ‘the beautiful game’ in a more celebrated fashion – in club nicknames.

The recent televised FA Cup tie between Brentford and Leicester City featured several shots of the London club’s badge – which features a bee. Brentford are nicknamed ‘The Bees’ and football writers have long loved the opportunity to craft match headlines centred around that favourite old phrase about a game having a ‘sting in the tail’. A late goal at Brentford is almost sure to provoke this phrase in some guise or other.

At one time the Brentford crest resembled a shield, and featured a traditional skep hive and a couple of impressively stout bees.  A recent make-over has delivered a modern round badge featuring a single bee which is now the proud focal point.

Brentford are pushing for promotion to the top flight, about to move to a sparkling new stadium, and football headline writers may go into overdrive if there they were to meet Watford who go by the nickname of ‘The Hornets’.

We can presume Watford’s nickname is intended to denote a menacing and powerful force. The connection can seem confusing when the club badge is clearly dominated by an image of a ‘hart’ or stag. Their ‘hornets’ nickname appears to date to the 1960s and is likely based simply on their predominantly yellow and black colours; there was only a brief window when the badge on their strip actually featured a hornet.

England doesn’t have a monopoly on insect nicknames.

In Scotland championship club Alloa Athletic are well known as The Wasps and their vivid gold and black hooped jerseys make the choice of this nickname an easy one to appreciate. Their Recreation Park home enjoys lovely views of the Ochils and Alloa may have had their nature inspired nickname since around the 1880s.

Perhaps not surprisingly the current Alloa club crest prominently features a wasp. It’s not a slavish representation by any means, and indeed has a cartoon element with the wasp depicted in a ‘superman’ pose complete with bulging muscles.  But the nickname has stuck over the years, as have the club’s colours, and as a consequence Alloa have a distinctive identity.

Football is a game steeped in tradition, and the retaining of insects in these nicknames and club crests is evidence of the importance of history to many football clubs. It also shows that folk notice insects in many different ways.

It is one thing to have an insect nickname, what about when the actual club is named after an insect?

Since 1886 that’s been the case in the Swiss city of Zurich, where one of the local football clubs is called Grasshoppers. It’s a fitting note to end on as they were in fact formed by a Scotsman – albeit going by the rather Welsh sounding name of Tom Griffiths. The name Grasshoppers is said to have reflected an energetic style of play and lithe athleticism. They visited Scotland in 1958 to play a floodlit friendly match in Glasgow, but apparently it was so foggy that evening it was hard to see from one end of the pitch to the other, let alone determine if the Swiss side lived up to their ‘springy’ name.

So insects and football.  Not an obvious relationship, but there nevertheless.