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The greater bulb fly


by Richard Jones

In the bright heat of this week's baking sunlight, a buzz of black and orange fur announces the arrival of what I think is one our cuddliest hoverflies.


The greater bulb fly, Meredon equestisIn the bright heat of this week's baking sunlight, a buzz of black and orange fur announces the arrival of what I think is one our cuddliest hoverflies. Merodon equestis is a large (12 - 15mm long), stout, bumblebee mimic, and although not quite as tubby as the bees it resembles, it makes up for it by carrying off a diverse array of colour-ways, mimicking a variety of bumble species.

Some specimens are almost all black, or with just the tail brownish red (just like the red-tailed bumble), some have shoulders and abdomen broadly beige and with a white tail (just like the white-tailed bumble), and some are tawny orange all over (just like the carder bees). Merodon always looks dapper and well-groomed, and perhaps that's the easiest way to tell it from the slightly scruffy-looking worker bees now just starting to forage.

I must admit that I take great glee in finding it in my garden, but some horticulturalists may not be quite so enthusiastic. Its English name, the greater bulb fly, gives away its secret. It is not one of those gardener-friendly hoverflies lauded for its voracious aphid-hunting larvae. Instead, its large glutinous maggots chew away at the insides of daffodil bulbs; at best leaving a large open wound in the damaged and weakened bulb, at worst completely destroying the plant.

I haven't got any daffs in my garden, but the fly is quite welcome to the Spanish bluebells that come up in vigorous drifts every year. In the wider countryside it is quite at home using native bluebells too. My fond attachment to this striking insect is also linked to an historical association with nearby Denmark Hill, only a mile or so from my house. Let me explain.

Merodon was not known in Britain until the middle of the 19th century. The prominent entomologist George Verrall reported with cool scientific detachment the fly's arrival in the UK, in his monumental monograph on hoverflies, published in 1901:

"M. equestris was not known to be a British species until I caught a specimen in my brother's garden at Denmark Hill in the South of London on June 8th 1869. Large quantities of Dutch bulbs were annually purchased by him for that garden, and I have scarcely any doubt but that the species was imported about that time; since then it has become abundant in districts where the bulbs of narcissi and allied plants are grown and the larvae have caused serious damage."

He then went on to enthuse about breeding times, colour forms and the insect's inexorable spread through England. Nowadays he would have to get straight on to the plant health inspector to report the discovery of a noxious pest.



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Gardeners' World Web User 26/05/2010 at 20:28

I was shocked the wonderful Japanese roof garden did not get Gold this year as it was so fabulously innovative and interesting and perfect its creator was able to explain it all to us

Gardeners' World Web User 06/06/2010 at 13:24

had bumble bees nesting under a sheet of plywood for about five years. we had to throw it away at last it was sooo tatty, and thought wed upset them. they now nest under the shed. whoopee

Gardeners' World Web User 07/06/2010 at 14:35

I've seen a buzzy thing that looks like this trying to bury under the soil in my garden in the last couple of months. I'm not sure if it's the same as this though. Do they make nests underground?

Gardeners' World Web User 09/06/2010 at 07:35

Reply to raggybaggy Although they lay their eggs on the exposed bulbs at soil level, the bulb fly is not equipped for digging. You are more likely to have found a solitary bee. This large group has several hundred UK species and they vary in size from small bumble down to large ant. Most look like small honeybees. Each female makes a single burrow in the soil, divides it into separate individual cells for her eggs and provisions each with a nectar/pollen cake.

Gardeners' World Web User 15/08/2010 at 21:07

Had some bees nesting low down near the ground seemingly behind a pot/small rhododendrun. Small, rust coloured bees. After a few days, wasps started going in and out of the same place and now no sign of any bees, just wasps. Do wasps invade/destroy/takeover bees nests?

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