Darwin wasps: The tiny killer pollinators

When it comes to pollination, we think of bees, flies and moths, writes Athayde Tonhasca. While these insects are crucial for the pollination of many of our crops and wildflowers, an enormous army of flower visitors carries on their business unnoticed by most of us: the Darwin or ichneumonid wasps (family Ichneumonidae).

The most commonly recognized wasps are social species whose females have venomous stings. In contrast, Darwin wasps have ovipositors (tube-like organs for egg-laying), and they are all solitary. They have a slender waist and noticeably longer antennae than other wasps. Most Darwin wasps are no more than a few millimetres in size, although some species are 7 cm long or more.


A Darwin wasp © Charles J Sharp, Wikipedia Creative Commons

We don’t know how many Darwin wasp species there are worldwide: some 25,000 have been described, but estimates of the true number vary from 60,000 to over 100,000. In the UK, we have approximately 2,500 known species, making up almost 10% of all British insects. In one study, 455 species were caught in a two-year period in a suburban garden in Leicester. So it is quite possible that Darwin wasps are one of the most diverse groups of animals on Earth.

Despite their diversity, Darwin wasps are largely overlooked and unknown. They are difficult to sample and identify, and details of their biology and ecology are lacking. One thing we know about them: the vast majority of species are parasitoids of other invertebrates – meaning they lay their eggs in or on a host, which the larvae feed on and eventually kill. This distinguishes them from parasites, which live off a host but don’t usually kill them, and predators, which attack and consume many individuals of the same or different species.

On hatching, Darwin wasp larvae initially absorb nutrients from the host’s body. Later they feed on non-vital organs, such as fat reserves. The host continues to feed and shows no signs of distress until the larvae are fully fed, when they finish off the host by eating its internal organs.  The parasitoids either pupate inside the carcass of their dead host, or they emerge and pupate in silk cocoons nearby. If you have seen the chest-bursting creature in the film “Alien”, you have an idea of the host’s predicament.


Darwin wasp larvae feeding on a caterpillar © Beatriz Moisset, Wikipedia Creative Commons


The apparent cruelty of these parasitoids troubled Charles Darwin, who refers to them in a letter he wrote in 1860 to the American naturalist Asa Gray:

I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of Caterpillars…”

This famous quotation is the reason why in 2019 a group of ichneumonid specialists proposed Darwin wasps as a vernacular name for this group of insects, so that they become more widely known and appreciated.

Darwin’s theological dilemma notwithstanding, “his” wasps are tremendously important as regulators of insect populations, including many pests. Several species are reared by biological control companies for use in gardens and glasshouses.

When not searching hosts, Darwin wasps can be seen feeding on the nectar and sap of flowers, shrubs and trees, although they prefer umbellifers (family Apiaceae or Umbelliferae) such as wild carrot, fennel and cow parsley. They are known to pollinate some of these species and some orchids as well, although we know very little about the extent of this ecological service. But considering the abundance of Darwin wasps, it would not be surprising if they turn out to be important pollinators in many of our habitats.


Darwin wasp Tryphon cf. rutilator © Hectonichus, Wikipedia Creative Commons

Building a meadow on the cheap

‘Building a meadow on the cheap’ is our guest blog today from Dave Pickett, Nature Reserves Manager, for Flanders Moss, Blawhorn Moss & Loch Lomond National Nature Reserves. Today he reflects on the story to create the Flanders Moss NNR car park wildflower meadow

Flanders car park meradow 2

Early 2016 and the car park at Flanders looked awful. After years of having a car park that also functioned as a wetland feature due to poor drainage the budget had finally been secured to put in a proper parking surface. But the budget didn’t go far enough to cover the costs of a planting scheme so though we had a beautifully drained parking area the surroundings looked pretty grim.


Flanders car park meadow 1The car park sits on heavy clay and some of this was used for landscaping. The dry weather that followed set the clay like concrete. None of this sounds very encouraging but on the Stirling NNR team we were keen to develop a wildflower meadow around the car park for a number of reasons:

–          It would be an appropriate welcome to a national nature reserve,

–          Any opportunity to create this type of habitat should be taken to support pollinators, especially in an area of intensively managed agriculture

–          A rich nectar source on the edge of Flanders Moss would give an opportunity to find what interesting invertebrate species might be found on the moss.

–          Flanders is very popular with photographers and an easily accessible wildflower meadow and its inhabitants would give them a different habitat to photograph.

So we had a wide expanse of clay, some willing hands (our volunteers) but only a little budget.

volunteers cutting and raking the meadow

In some ways the clay was a good starting point as being infertile means that it is easier to get wildflowers to establish as the grass growth is less vigorous. We had enough budget to buy a small number of wildflower plugs and these our team of volunteers planted.

Gradually through the first summer a vegetation covering appeared and the harsh edges of the car park softened. But we needed to fill the gaps to get a better covering of wild flowers.

One of the best plants to introduce is yellow rattle. This is semi-parasitic on grasses so restricts their growth leaving spaces for other species to come in the gaps. We were lucky because one of the farmers that owned a bit of Flanders Moss grew organic hay that had plenty of hay rattle in the meadows. So just when the hay rattle was starting to set seed on the farm we went in and sent a day pulling it, putting it into ton sacks and took it back to spread across the meadow.

yellow rattle harvesting

The next year this free seed source gave rise to a good scatterings of yellow rattle on the meadow. To add to this that autumn we collected seed from two  local wildflower species  — common knapweed and meadow vetchling.

Both these flowers have large obvious seed heads and pods so we picked a bucket full of each and took it back to the office. There I laid the seeds out on the office floor on trays to dry out so that they would keep better.  Each morning I came in to find the trays and seeds disturbed and knocked about. I was busy blaming the cleaners for not taking care until a few weeks later found mass of seed pods and seed coverings in a plug well under my desk. It would appear that the office mouse had thought Christmas had come early and had tucked in, a nice thought to have a bit of wildlife inside our hyper-corporate office in a Stirling business park!

Even with a reduced seed stock that winter we took a rake to the meadow surface to scarify the surface and the scattered the seeds across the meadow following up with a bit of stamping in in lieu of a roller.  Though I am sure that we had a low conversion rate from seeds to plants it still proved to be a low cost way of improving the meadow with meadow vetchling and common knapweed plants getting more obvious each year.

Four years in and the meadow is starting to look like a meadow.

There is still plenty of work to do. We have to cut and rake the cuttings each autumn with the help of our volunteers, there is scope of more scattering of collected seeds, the soft rush, docks and creeping thistles need to be kept in check to allow the wildflowers space and I have yet to find someone willing to take on trying to I.D. some of the pollinators using the meadow.

But we always knew this would be a project of slow development, and each spring I look forward to seeing how the meadow looks as the seasons progress. If you visit Flanders in the summer it is well worth spending a little time checking out the wildflowers in the car park before heading out for the joys of the bog.

The life and troubles of the orange-tailed mining bee

The season is picking up and the first pollinators are already out, scouting for nesting sites and food, writes Athayde Tonhasca. It’s a harsh start, as cold spells may be deadly and flowers are still scarce. The orange-tailed mining bee, also known as the early mining bee (Andrena haemorrhoa) is one of the first bees to emerge in the spring. The female bee has bright, rusty red hairs covering her thorax – hence the inspiration for the species name, which derived for the Greek haima (blood) and rheo (flow); the same roots as ‘haemorrhage’. There is a tuft of red hairs at the tip of the abdomen as well, which helps distinguish this bee from others of similar colour.


Andrena haemorrhoa © Pauline Smith.

The orange-tailed mining bee in found in a variety of habitats, and like other mining bees, it nests underground. This bee is not picky at all: it will excavate its nest in parks, playing fields, gardens lawns, paths, roadsides – any open, dry spot with light soil will do, especially on south-facing slopes and banks. A little pile of spoil around a hole in the ground is a tell-tale sign of a nest. Several bees may nest next to each other, but that’s because they are all making use of a suitable nesting site: each bee will build its own nest and ignore the others.



A mining bee nest entrance.

At this time of the year you may find orange-tailed mining bees visiting the few spring-flowering plants such as dandelions, blackthorn, willows and gorse, but its diet will expand as the season progresses. In fact, this bee is one of the most frequently recorded species on flowering crops grown in the UK. It is also one of the pollinators of the Lady’s slipper orchid (Cypripedium calceolus), which is critically endangered in many countries.

But it’s not all rosy for this pollinator: a fork-jawed nomad bee (Nomada ruficornis) may be lurking, flying close to the ground in search of an orange-tailed mining bee nest. Once a nest is found, the nomad bee uses its sense of smell to tell whether the nest is stocked with pollen and its owner is nearby. If conditions are right, the nomad bee will invade the nest, sometimes kill the host’s offspring, lay her eggs and leave. The invading bee larvae will eat the host’s larvae if their mom has not already done so, then will eat each other until only one is left alive. This larva will then feed on the pollen and nectar stored by the host bee. This type of parasitism is known as kleptoparasitism (parasitism by theft) or brood parasitism, and these parasites are known as cuckoo bees.


Nomada ruficornis © Janet Graham, Wikipedia Creative Commons.

Over 3,700 parasitic bee species have been described (at least 850 of them from the genus Nomada). Most of them are host-specific, and some are threatened. If you are wondering why we should protect a bee-killing species, think about other loved, charismatic creatures that are no less deadly to their prey such as dragonflies, owls, eagles and wildcats. Cuckoo bees are marvellous examples of natural selection and evolution, and they do no less than their hosts to be successful and survive.

Solitary success story

Most people are familiar with honey bees and bumble bees. These are social insects that live in colonies, each consisting of a queen and her many workers.  However, in Britain just under 250 species of bee are solitary, and as Athayde Tonhasca reveals, they are often closer to us than we might imagine.

As the name suggests, solitary bees live alone: there are no queens or hives. Having said that, it is the case that some nest in colonies, where sometimes a shared entrance leads to individual chambers. At this time of year you may glimpse some of their comings and goings.

Solitary bees use a variety of nesting sites.  Some nest in tree holes, others opt for cracks in dead wood or stones; but most select places in the ground.

Some chocolate mining bees (Andrena scotica), picked this wall for their homes.

Some chocolate mining bees (Andrena scotica), picked this wall for their homes.

In Perth last year there were several opportunities to watch chocolate mining bees going to and from their nests.  Behind the wall in the picture, each female bee dug out tunnels and built chambers in which she laid eggs and stocked pollen to support the larvae after hatching.

Solitary bees are excellent pollinators, but perhaps not as highly regarded as they don’t produce honey or wax, nor are they as easy to identify as bumble bees and honey bees.

Solitary succes pic

They are docile and harmless: please help protect them and their nesting sites.

The range of solitary bees is remarkable. Our colleagues at Buglife Scotland built a sandy bank at Forge Dam a couple of years ago, and last year it was by covered with bees digging their nests.  The red mason bees at SNH’s Battleby office were also very active last year; using the masonry of one of the buildings as well as the nearby bee house.

If you want more information about solitary bees, contact athayde.tonhasca@nature.scot


What’s in a name?

The naming of moths is a difficult matter

It isn’t just one of your holiday games;

You may think at first I’m mad as a hatter

When I tell you a moth must have two different names

Entomologist John W. Brown, inspired by T.S. Elliot


Some people are intrigued by scientific names, and others think of them as just academic snobbery, writes Athayde Tonhasca.  If we see a honey bee, why call it Apis mellifera? Well, there are at least seven species of honey bee around the world. In Britain we only have Apis mellifera, but in certain parts of Asia, a honey bee could be Apis cerana, Apis koschevnikovi, or Apis nigrocincta. And even though we have a single honey bee species, it has two common names: the western honey bee or the European honey bee.

Common names are imprecise and potentially confusing; the bird we call ‘robin’ in Britain is the species Erithacus rubecula; in North America, a ‘robin’ is a bird related to our blackbirds, Turdus migratorius. The name ‘badger’ refers to various animals worldwide that are superficially similar but are not closely related to each other: our badger, Meles meles, is not the same badger found in North America (Taxidea taxus), which is different from the Asian badger (Mellivora capensis), and so on.

In contrast, scientific names are used all over the world, avoiding confusion and the difficulties of translation. The second largest predatory cat in the Americas may be called a cougar, puma, mountain lion, red tiger or panther (and many other names in other languages), but to a zoologist it is always Puma concolor. It crosses all linguistic barriers, and allows no ambiguity.

But why use Latin, a dead language? For centuries, Latin was the international language of science, philosophy, religion and diplomacy. Carl Linnaeus (1707–1778), the Swedish botanist who disseminated the method of naming species in two parts (binominal nomenclature), wrote in Latin, and so did other scientists and educated people across much of the world. Also, Latin has two advantages. As it no longer evolves and changes like modern languages do, it provides a stable, reliable tool to generations of taxonomists. And it does not favour any particular national language or culture.

The first part of the scientific name identifies the genus to which the species belongs. A “genus” (plural “genera”) is a group of related species such as Apis. The second part (the epithet) identifies the species within the genus, such as mellifera. By convention, the genus is always capitalized, while the epithet is always in lower case. And the whole name should be printed in a font different from that used in normal text, usually italics. A binomial name is treated grammatically as Latin, but the two parts can each be derived from a number of sources. For a long time, well-educated people were taught Latin and ancient Greek, so names derived from these two ancient languages were, and still are, used frequently. For example, our own species, Homo sapiens are Latin words meaning “human/man” (Homo) and “wise” (sapiens). The genus Rhododendron was named by Linnaeus from a Greek word derived from rhodos, (rose) and dendron (tree). So there you have the basic rules of expressing a scientific name.

There is another important reason for naming species. It allows us to talk and think about them individually. Every time a new species is described, it is like a ‘birth certificate’ has been issued. If we don’t know the names of animals, plants and other organisms, it is difficult to draw up legal protection plans, study them or stir public interest. The number of animal species on Earth is estimated to be around 8 million, but only 12% of them have been named. We can’t properly measure life on the planet without naming more of those species.

Every name has a story, and sometimes the story is poignant. The bumble bee Bombus rubriventris is known from a single specimen collected at least 180 years ago, but we have no other record or any information about it. This specimen was probably collected in the Brazilian Atlantic Forest, which has suffered extensive habitat degradation over the centuries, and today little of it remains. So the sole creature in the world named Bombus rubriventris siting inside a dark drawer in an insect collection in Oxford is the only evidence of a bee that once buzzed from flower to flower in a tropical forest, and which has been lost forever.


Bombus rubriventris

Image copyright, Paul Williams, 2014, Journal of Natural History, http://dx.doi.org/10.1080/00222933.2014.954022. © Natural History Museum, London.

Science on your doorstep

During these unsettling times, the majority of us will be keeping safe in our homes and gardens. Adjusting to these new patterns of life can understandably be difficult – many of us will be missing our favourite green spaces or struggling to keep young children entertained. To help, Apithanny Bourne has put together a list of pollinator and botany themed citizen science projects, which can all be enjoyed from the safety of your garden, window box or computer screen!

  1.  Zooniverse

First of all, we understand that not everybody will be lucky enough to have access to a garden or area of greenspace at the moment. This is why we want to make you aware of the fantastic citizen science website Zooniverse. Whilst it’s not quite the same as experiencing nature outdoors, you can help researchers analyse data from real projects around the world. You might get involved with deciphering herbarium samples, watching nest box cameras or counting seabirds from photographs. Keep your eyes open for any pollinator themed projects which might appear.


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2. UK Pollinator Monitoring Scheme (FIT count)

If you are lucky enough to have a garden, you may well be able to perform a Flower-Insect Timed (FIT) count. This survey involves observing insects visiting flowers over a 10-minute period, beginning in April. The project specifically asks you to observe particular species of plant – including dandelions, a common plant in garden lawns UK wide! The scheme uses this data to build a picture of changing pollinator populations across the country.


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3. Garden Butterfly Survey

Butterflies are regular garden visitors and Butterfly Conservation UK would love to know which species you have spotted. This useful data allows scientists to track the population trends of some of our widespread species, which have sadly suffered drastic declines. It’s easy to submit your records via the Butterfly Conservation website, or the handy irecord Butterflies free mobile app. Both contain identification guides if you are feeling unsure about your butterfly sighting!



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4. Bee-fly Watch

Bee-flies are rather adorable flies which have a fluffy appearance and a long proboscis, which they use to feed on nectar from flowers. You can spot their distinctive hovering over flowers between the months of March and June, and Bee-fly Watch UK would love to hear about your sightings. This lovely spring insect is not to be missed and you can follow all the action using the hashtag #BeeFlyWatch on Twitter.


5. Hoverfly Lagoons

Hoverflies are often overlooked, despite many of them being attractive and important pollinators. This project is fun and especially child friendly – all you need is an empty milk bottle and some grass cuttings or leaves! You are asked to create an artificial “rot hole” which some common species of hoverfly require for egg laying. Once created and nicely rotten, you can record the number of hoverfly larvae found in your lagoon.


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6. Garden Moth Scheme

Moth trapping is a rewarding and engaging activity – great for adults and children alike. This survey requires a moth trap and so may require a little investment if you don’t have one already. You can construct a budget trap using the guidance below or order one from a supplier. This survey asks you to put out your trap once per week and submit your records.



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7.  Beewatch

Beewatch is a collaborative research project between Aberdeen University and the Bumblebee Conservation Trust. This online tool uses technology to assist participants in improving their bumblebee identification skills and provides computer generated feedback. It also uses crowd sourcing by allowing competent users to help in identifying other users bumblebee photographs.



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8. UK Ladybird Survey

The UK Ladybird Survey aims to encourage the recording of all species of ladybird found within the UK – including the invasive harlequin ladybird. On their great website you will find lots of information to help you find and identify species, and online forms so that you can record your observations.


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9. Grassland Mapping Project

This is another project you can support from the comfort of your computer screen – although it does require some prior knowledge of species rich grasslands in your local area, if you are lucky enough to have them. Unfortunately, we have lost over 97% of our meadows in Britain in less than a century, largely due to changes in land use. Scottish Natural Heritage have launched the grassland project to help locate and protect Scotland’s remaining fragments of meadow. Read more about grasslands in this interactive story map and click the button at the end to submit records of sites.



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10. Silphidae Recording Scheme

The National Silphidae Recording Scheme collates records for beetles in the family Silphidae – a very interesting group of insects, many of them associated with carrion (dead animals). The good news is that some of the more colourful species in this group are also attracted to light, so if you use a garden moth trap you are likely to end up with a few silphid visitors. The website for the scheme contains an excellent interactive PDF key to identifying the most common beetles you may encounter.


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These featured projects represent just a few of the many citizen science opportunities you can get involved with at home. We have chosen to feature insect and plant themed projects, however there is something for everybody depending on your interests. The Garden Birdwatch is a great one to do from a window, whilst the Garden BioBlitz is a fun in-depth survey covering all types of wildlife.



Stay safe and have fun enjoying the nature on your doorstep.


All pictures courtesy and copyright of Apithanny Bourne.



Natural bookshelf

For those of us who enjoy natural history books we have been living in a ‘land of plenty’ of late. It seems that barely a month passes without another exciting new title added to the list of good reads.  In amongst the blizzard of publishing activity books about bees have certainly had their moment in the sun, and in this short article we take a look at just a handful of titles you might enjoy.

IMG_0376 2

It is fair to say that Professor Dave Goulson took the literary world by storm with his unique mixture of insight and humour in ‘A Sting in the Tale’. It’s a few years since that excellent title re-ignited interest in natural history books up and down the country, and not unreasonable to say it fuelled something fresh in the publishing and nature writing circles.

By his own admission Dave grew up obsessed by insects, and wildlife in general. Now Professor of Biology at Sussex University he has published over 200 scientific papers on bumblebees and other insects, and in 2006 he founded the Bumblebee Conservation Trust, a charity which now boasts over 7,000 members.

Professor Goulson made the leap from academia to popular writing with incredible success and style. His main gift is that he is superbly able to demystify complex themes and detail, whilst retaining a dash of humour and a pleasing conversational tone.  Little wonder his work has featured on Radio Four’s Book of the Week as well as being shortlisted for the coveted Samuel Johnson Prize.

A Sting in the Tale’ introduced a whole new readership to bumblebees, and was followed by other titles all of which have featured bees in varying degrees. ‘A Buzz in the Meadow’, took the reader on an interesting journey to France where Dave used his small landholding to create and study a mini wildlife reserve. ‘Bee Quest’ was much more widely travelled and the author recounted visits to the Hebrides, Ecuador, Patagonia and Poland. Again the story was told in a fashion that was both compelling and hugely informative. And in his latest book ,‘The Garden Jungle’, Dave makes a plea that we all plant for pollinators. That seems a good point for his progression of highly enjoyable books to have reached.


Thor Hanson’s ‘Buzz’ highlights the American experience and spends a deal of time looking at California and Florida. He analysed a range of subjects from solitary bees and almond orchards to the transportation of bees across America to pollinate crops. His was an interesting read that highlighted practices that entomologists had long been aware of and held a deep interest in, but which hadn’t made it into the public domain with quite the force that might have been expected.

For those seeking fiction, then Maja Lunde’s ‘The History of Bees’ may fit the bill.  It’s a story set in three different time-frames. From China 2098 back to the United States in 2007 and England in 1851 it focuses on the role of bees, our inescapable connection with them, and how successive generations of beekeepers have faced different challenges.



Climate Change is a key theme in this fascinating novel which many have suggested could prove as thought provoking as Rachel Carson’s Silent Spring. Another strand running through this novel is culture and how place, economics and time have dictated the ways in which people interact with pollinators.

As we contemplate more time spent at home books will be increasingly important. If nature sparks your imagination, then the above might just help ease you through the weeks ahead.