Dead lions, dandelions, treacle & cesspools – the many facets of the drone fly’s life

By Athayde Tonhasca

If you take a close look at a tin of Lyle’s Golden Syrup or Black Treacle, you will notice one of the most unappetising and strange food logos: a dead lion surrounded by a swarm of bees above the slogan ‘Out of the strong came forth sweetness’. The image and text are based on the Biblical tale in which Samson kills a lion, and later finds a honeycomb inside it. This supposedly inspired Samson to write a riddle: ‘Out of the eater came forth meat and out of the strong came forth sweetness’. The meaning of the riddle is that Samson had meat and honey (sweetness) from the carcass of a lion (the eater and the strong).

The story apparently inspired the stanch Presbyterian Abram Lyle (1820-1891), businessman and founder of the sugar refinery Abram Lyle & Sons. So one of Britain’s oldest brands was born; its logo remains virtually unchanged since 1885.

Lyle’s Black Treacle. © Athayde Tonhasca.

The yarn about dead animals and bees is more than 2,000 years old: the Greeks, the Romans and other Mediterranean peoples believed honey bees originated spontaneously from animal carcasses, primarily those of oxen. The Greeks had a name for this miracle: bugonia, from bous (ox) and gon (generation). The Roman poet Virgil (70-19 BC) describes the story of a farmer, who in want of bees, slaughtered an ox and waited for a new swarm. Bugonia inspired Shakespeare as well: ‘Tis seldom when the bee doth leave her comb, in the dead carrion’ (Henry IV).

Bugonia, unknown author, 1517 © Wikipedia Creative Commons.

Corpse apiculture suffered a serious blow in 1668, when the Italian physician, naturalist, biologist and poet Francesco Redi (1626-1697) published Esperienze Intorno alla Generazione degl’Insetti (Experiments on the Generation of Insects). With simple experiments involving the covering of meat-filled glass containers and observing the presence or absence of flies and maggots, Redi put an end to the belief in spontaneous generation.

Bugonia was dead, but the recurrent reports of bees swarming around carcasses, just like in Lyle’s logo, still required explanation. Enter diplomat and entomologist Baron Karl-Robert von Osten-Sacken (1828-1906), who, despite his Teutonic-sounding name, was Russian. The Baron suggested that the ‘bees’ found around dead animals were in fact flies: not the expected carrion-seeking blow flies and bluebottles, but the drone fly, Eristalis tenax.

The drone fly is native to Europe and one of the most common British hoverflies. In some years populations are boosted dramatically by immigration from the continent. The name ‘drone fly’ comes from its resemblance, in appearance and behaviour, to honey bees. Males are territorial, chasing away other males and even bees, wasps and butterflies. The adults feed on pollen, especially from yellow flowers such as dandelions, and they are known to pollinate various crops including onion, kiwifruit, soybean, sweet pepper and carrot: they may contribute to the pollination of wild plants as well. The drone fly can be as efficient as the honey bee in transferring pollen between plants, so it is one of the few fly species being evaluated for mass production and release in greenhouses.

A male drone fly. Like many fly species, males have larger eyes that almost touch, while female eyes are spaced apart. © Wikipedia Creative Commons.

After mating, females lay eggs near dirty, contaminated water such as manure lagoons, holding pits in livestock areas, ditches and wet silage. The larva has a long ‘tail’, which is a specialized respiratory structure that works as a snorkel, allowing the insect to breathe air from the surface. This respiratory appendage gives the larva its common name: the rat-tailed maggot.

A drone fly larva, or rat-tailed maggot. © Wikipedia Creative Commons.

In his 1894 publication ‘On the oxen-born bees of the Ancients (bugonia) and their relation to Eristalis tenax, a two-winged insect’, Baron von Osten-Sacken explained the bugonia phenomenon as this:

‘The original cause of this delusion lies in the fact that a very common fly, scientifically called Eristalis tenax (popularly the drone-fly), lays its eggs upon carcasses of animals, that its larvae develop in the putrescent mass, and finally change into a swarm of flies which, in their shape, hairy clothing and colour, look exactly like bees, although they belong to a totally different order of insects.’

The Baron came close: the drone fly does not lay its eggs on carcasses, but on their liquid exudates and foul water accumulated around them. That’s why the drone fly is important in forensic investigations involving partially submerged human corpses.

Hence an entomological mystery appears to have been solved. Next time you spot a drone fly busy pollinating flowers in your garden or local park, pause to consider the long thread that links it all the way to our ancient legends and history.

The Times They Are a-Changin’

By Caroline Anderson

I don’t know about you but I feel that summer was just getting started and now there are signs of it coming to an end.  At Taynish the leaves on the cherry trees and the rowan berries are turning red – surely not already!  Maybe it’s just been such a weird year that things seem out of order, but I know I’m not quite ready to prepare for autumn.

Like the seasons the insects that perform such an important job have their peaks and troughs.    The abundant red and blue damselflies are now a rare sight but thankfully, there are still plenty of pollinators and plants in bloom around to enthral and delight.    The devil’s-bit scabious is flowering and attracting all sorts of wonderous things clamouring for a share.

There are also plenty of butterflies around just now, particularly the Scotch Argus with its figure of eight markings,

And Speckled Wood, this one looking a bit the worse for wear following some heavy rain and winds.

A never-ending source of amazement for me is that the Peacock butterflies have gone from this….

to this, fresh out the box specimen in all its colourful glory …  what a transformation!

The bees and hoverflies continue to hoover up all the pollen they can find – with the knapweed being a favourite.

As always the boardwalk at Taynish is a favourite haunt for me, as indeed the bog itself – soggy work but it always pays off.   In my last squishy wander I found Mr & Mrs Emerald Damselfly sunning themselves – the Mrs is the very green one with the Mr being the bluer of the two.

But the boardwalk didn’t stop there – it also provided the opportunity to photograph the beautiful, and very quick, Black Darter, very similar in shape to the common darter but very obviously black.  So lovely to see them back again this year.

The bog also gave up this lovely wee moth, a Brown China Mark with its very elaborate markings.  Moths are very often just as pretty as butterflies, but are much maligned.  Moths are amazing pollinators as they very often take over from the bees and butterflies as the sun goes down and work the night shift.

If you visit Taynish at the moment you will not be disappointed, lots to see at every turn, with the added bonus of an exhibition at the mill.   This year the Snapberry project had to be a bit different from normal.  The pupils from Lochgilphead High School were challenged to take photos using their phones whilst on their daily exercise or from their garden.  Their submissions were absolutely wonderful and gave an insight into their #lifeinlockdown exhibition can be viewed at the mill.

The narcissus bulb fly, a fly in bee’s clothing

By Athayde Tonhasca

By now your garden or local park must be buzzing with bees, hoverflies and butterflies, all feverishly stocking up on pollen and nectar. Bumble bees are some of the most conspicuous flower visitors, and easily recognisable by their coloration and hairy bodies. But if you take a close look at them, you may spot an impersonator: the large narcissus fly, also known as the narcissus bulb fly, Merodon equestris.

The narcissus bulb fly © Frank Vassen, Wikipedia Creative Commons

By resembling a bumble bee, this hoverfly has a better chance of being left alone by predators on the lookout for a meal but not willing to risk being stung. From this video, you may say you can easily tell a hoverfly from a bumble bee. However, perfect likeness is not necessary; all it takes is the predator’s slight hesitation. It may give the fly the opportunity to buzz away, or divert the predator’s attention towards another victim, apparently less threatening.

The selective process that leads a harmless species to resemble a dangerous one, thereby gaining protection from predators, is known as Batesian mimicry. British naturalist Henry Walter Bates (1825-1892) figured out this powerful example of natural selection while studying butterflies in the Amazon rainforest.

Hoverflies (family Syrphidae) comprise one of the largest groups of flies, with more than 5600 species described worldwide. We know more about the European fauna: of the 630 or so species, at least 138 (~22%) are mimics of bumble bees, honey bees or social wasps. Some hoverflies don’t copy just the appearance of dangerous insects, but their behaviour as well. The wing-flapping and abdomen-tapping of the fly in this video imitate the manners of a wasp. But the charade goes further: the fly extends the forelegs in front of its head to create the impression of having antennae as long as wasps’. The whole performance signals “don’t mess with me, I can sting you”. Clever, you must agree.

A narcissus bulb fly visiting a flower © Donald Hobern, Wikipedia Creative Commons

Narcissus bulb flies are not welcomed in gardens because their larvae feed on bulbous plants such as daffodils, narcissuses and bluebells, and can be quite destructive. However, as often is the case in nature, there is another side. Hoverflies in general are important predators of aphids, which cause significant damage to crops worldwide. They are also frequent visitors to a wide range of wild flowers and agricultural crops, and are considered the most important group of pollinators after bees. In some situations they are the most effective pollinators, inducing more seed production than any other group of insects.

It seems there is more to the narcissus bulb fly than being a well camouflaged garden nuisance.

 

From adorable fuzzball to menacing rascal: the two lives of the buff-tailed bumble bee

By Athayde Tonhasca

In 2005, the buff-tailed bumble bee (Bombus terrestris) came out first in a poll to elect UK’s favourite insect. This wasn’t surprising: the buff-tailed is one of the most common bumble bees in the country. It is relatively large, easily recognisable and one the first bees to be seen in spring. So you could say this species is an ambassador for all those lovable and cherished bees: “surely, everyone knows the great furry bumble bee, that gentle giant of the blossoms, that somehow awkward, slow, bumbling bear of a bee” (Brian L. Griffin). Beatrix Potter probably had the buff-tailed bumble bee in mind when creating Babbity Bumble.

Beatrix Potter’s Babbity Bumble in The Tale of Mrs Tittlemouse, 1910. Image in the public domain.

This bee is an excellent pollinator of a variety of crops and wildflowers, especially because of its ability to extract pollen that is firmly packed into the flowers of plants such as tomatoes, blueberries and aubergines. The buff-tailed is resourceful and adaptable: it forages over long distances, is not too sensitive to bad weather or picky about habitats. These characteristics help explain why their numbers remain strong and their populations seem to be expanding, while some bumble bee species have suffered declines.

Bombus terrestris. © U.S. Geological Survey Bee Inventory and Monitoring Lab.

In the 1980s, Belgian and Dutch companies developed techniques to rear bumble bee colonies on large scales, and an industry worth millions of pounds was born. Mass-produced buff-tailed and other bumble bee species replaced labour-intensive mechanical methods of pollination, and today every European tomato is pollinated by a captive-bred bumble bee. Commercial bumble bees made their way to farmers in the Americas, Japan, Australia and other countries to pollinate greenhouse crops such as tomatoes and peppers. And then trouble began.

The qualities that make the buff-tailed so well suited to its native habitat are the same that make it an invasive species elsewhere. When imported buff-tailed bees escape from greenhouses – and insects always escape – they become established and outperform native pollinators in the search for nest sites and food. They also carry novel diseases that are transmitted to the local fauna.

The impact of these man-made invasions has been demonstrated nowhere better than in South America. The buff-tailed was introduced to Chile in 1998, and thanks to a dispersal rate of up to 200 km per year, it rapidly invaded Argentina and spread out through most of the country. It is expected soon to cross into Uruguay and Brazil.

Brazilian Extension Service ‘wanted bee’ poster encouraging the public to notify sightings of buff-tailed bumble bees. Image in the public domain.

Wherever the buff-tail arrived, the native Patagonian bumble bee (Bombus dahlbomii) declined sharply or disappeared altogether, whether because of competition or infection by a parasitic protozoan brought in by the buff-tailed. Nobody knows for sure. As a result, the Patagonian bumble bee, the world’s largest, in now on the list of globally threatened species. The ecological damage caused by the buff-tailed goes further: this interloper pollinates and possibly helps the spread of invasive plant species, and reduces the volume of nectar available to hummingbirds.

A Patagonian bumble bee. © U.S. Geological Survey Bee Inventory and Monitoring Lab.

Similar scenarios have played out in the USA and Japan, so today many countries prohibit the importation of buff-tailed and other exotic bumble bees. Mass-produced bumble bees have an undeniable economical value, but they also have been identified as one of the emerging factors affecting global diversity.

The buff-tailed bumble bee is another Dr Jekyll and Mr Hyde tale of unintended consequences of species introductions. There may be compelling reasons to do it, but the possibility of harm should never be ignored.

 

The all-important tongue

By Athayde Tonhasca

The bees in our gardens and parks seem to hop aimlessly from plant to plant, without a flight plan. However, the flowers they are able to pollinate depend on one feature of the bees’ anatomy: the length of their proboscis (the insects’ tongue).

A bee’s tongue is long, flexible, hairy and grooved. It lays between mouthparts called palps and maxilla, which form a protective sheath. When the bee is flying or resting, it keeps the tongue folded under its head. When the bee wants to feed, it sticks out its tongue to lap the liquid in rapid back and forth movements.

A bumble bee tongue © Macroscopic Solutions, Wellcome Collection, Wikipedia Creative Commons.

But why would the size of bees’ tongues matter? Flowers of plants such as brambles and oilseed rape are shallow, which makes them available to most visitors. But plants such as foxglove, honeysuckle, field beans and red clover have long, deep flower tubes (corolla), thus their nectaries are inaccessible to short-tonged species. The garden bumble bee (Bombus hortorum), for example, is one of the few visitors to foxglove and honeysuckle thanks to a tongue about 14-mm long. But these plants are largely out of reach of another common garden visitor, the buff-tailed bumble bee (B. terrestris), which has a tongue of around 8.5 mm.

Charles Darwin noted this aspect of pollination ecology in the On the Origin of Species (1859):

“From experiments which I have tried, I have found that the visits of bees, if not indispensable, are at least highly beneficial to the fertilisation of our clovers; but humble-bees alone visit the common red clover (Trifolium pratense), as other bees cannot reach the nectar.”

— A long-tonged bumble bee (L) and a short-tonged mining bee (R). © U.S. Geological Survey Bee Inventory and Monitoring Lab.

Tongue length matters not only to bees: pollination by hummingbirds, bats, moths, and flies depend on correct matching with the depth of flower tubes.

We may be tempted to conclude that long-tongued species have an advantage because they can take nectar and pollen from deep and shallow flowers. However, a long tongue can be an obstacle, as explained by Professor David Goulson’s analogy: a soup ladle is great for scooping up broth from the bottom of the pot, but it doesn’t work well for eating a bowl of soup. Indeed, long-tongued bees can feed on shallow flowers, but they usually do it slowly and inefficiently.

Short-tongued bees are mostly excluded from deep flowers – “mostly” because these bees can find their way to hidden nectar: see Crime and nourishment in the heathlands. On the other hand, they can forage more quickly on shallow flowers, so they don’t expend much energy gathering nectar.

Being aware of tongue lengths will help you make your garden more attractive and useful to bees and other pollinators. The greater the variety of flowers, the better: alliums and daisies for short-tongued species; trumpet-shaped flowers such as foxgloves, bluebells, comfrey, borage, penstemons, snapdragons and lungwort for the long-tongued ones. Plants bred for double flowers are of little use, as they often produce little or no pollen and nectar, and pollinators cannot get through tightly packed petals.

From Trojan battlefields to Pooh Corner

Around 8 BC, Homer wrote The Iliad. This epic about the Trojan War features the likes of Agamemnon and Achilles; honey bees get a passing mention. Bees have been appearing in stories ever since, and today they show little sign of disappearing from our pages.

Honey bee feeding on a garden sedum. ©Lorne Gill

In The Illiad they were seen as an inspiration to warriors, so ferociously do they resist attack. Homer, however, wasn’t breaking entirely new ground with his bee observations. We see bees in hieroglyphics, which takes us back to around 3500 BC, and it is therefore perhaps no surprise that bees have subsequently featured in some of our most popular literary works.

For Pliny the Elder the admiration was altogether different. He wondered how honey bees, despite visiting a variety of flowers, made a single honey.

If Homer and Pliny focused on the fighting and feeding prowess of bees, Karl Marx, in On Capitalism, was drawn to their organisational abilities and appreciatively compared them to the most skilled of architects. Charles Dickens on the other hand was a little less flattering in Bleak House. Over breakfast, one of the book’s characters savours his honey but wonders about the bees being so easily ‘smoked out of their fortune’.

Henry V was published around 1600, and in this play Shakespeare compared a well-run  country with the collective effort of a honey bee colony. That’s been an enduring theme in literary references.

Silvia Plath, whose father was an entomologist, wrote several poems in the 1960s about honey bees in which the focus ranged from the craft of beekeeping to the fate of swarms. There is also a telling view of working with bees in Thomas Hardy’s Far from the Madding Crowd, when Bathsheba looks to gather up a swarm.

One of the most thoughtful passages on honey bees is found in War and Peace, where Leo Tolstoy fondly observes the various functions and activities carried out by bees and why people, depending on their experience of bees, formed a different view of their purpose.

A bee settling on a flower has stung a child. And the child is afraid of bees and declares that bees exist to sting people. A poet admires the bee sucking from the chalice of a flower and says it exists to suck the fragrance of flowers. A beekeeper, seeing the bee collect pollen from flowers and carry it to the hive, says that it exists to gather honey.

Tolstoy was clearly a student of bee behaviour as he also used an empty beehive as a metaphor for Moscow on the eve of Napoleon’s invasion

Roald Dahl authored many a scary story, and in Royal Jelly a beekeeper  takes royal jelly and then feeds it to his baby, with startling results. A recent thriller, Coffin Road by Peter May, also features honey bees, with the main character a scientist involved in studying the effects of neonicotinoids on bees.

We are likely to come to authors such as Homer, Marx and Tolstoy as adults, not so A.A. Milne, whose children’s classic Winnie the Pooh books are laced with references to bees.

When we are introduced to this bear we quickly learn of his love of honey. An incessant buzzing noise alerts Pooh to the presence of honey bees whom, as far as he is concerned, have but one purpose in life – to make delicious honey. Reaching a hive in a hole high in a tree poses a challenge, and gave us the famous drawing of Pooh floating beneath a balloon as he tries to reach the nest. The adventure ends badly, but later in the novel we do see the hapless bear united with jars full of honey.

Whatever your age, whatever your bookish preference, you can be sure that at some point in your reading life you will come across honey bees. And if you touch upon a few of the above, you are in for a treat.