Beauty and the Beasts

The world of flies is truly fascinating. There are over 100,000 species world wide, with more than 7,000 recorded in the UK. The ability to identify them would require a lifetime of learning and endless patience - neither of which I have. I enjoy the challenge of identifying a new find, but I also end up throwing away dozens of pictures because I cannot spare anymore time researching them. However, I can always make time for the unusual.

The Beauty - Phasia hemiptera

Amazing colours on this fly. I spent a couple of hours trying to identify it, before I realised that I had seen it and photographed it before, but under different lighting conditions. The colours were there but not quite as obvious.


Reading up on colours in flies wings, it appears that there is another world of colour in flying insects. We do not see it but it is probably a key means of communication between flies, bees and wasps. Photograph a flies wing against a white background and it will probably appear as transparent, with no colour, as the reflected white light swamps the picture. Photograph it against a black background and with the correct lighting conditions and the colours become apparent.

I haven't yet pulled out any flies wings to try it out but there are good examples on the web. Have a look at this National Geographic article.


The picture below shows the three dimensional structure of the same flies wing, which I had not really noticed before. A quick check shows that there is a huge amount of research going on in this area. Clearly it has implications on manoeuvrability in man made flying objects.

Now for the beasts. Some of those flies that make you step back if they land close or fly near to you.


Robber flies, members of the Asilidae family and distant relative of the common housefly. These are amongst the top predators of the insect world. They feed on a wide range of prey, including other flies, beetles, butterflies, moths, various bees, dragonflies, damselflies, wasps, grasshoppers and some spiders. They wait in concealment and dart out to capture their prey using the long legs to hold them still. They then use a short, strong proboscis, to stab and inject victims with saliva containing neurotoxins and enzymes. These paralyze the victim and starts the digestion  of the victims soft tissues. The Robber Fly then sucks the prey dry.

Most are also capable of delivering a painful bite, so should be handled with care. Below is a Common Awl Robber Fly coming in at body length of about 15-17mm.


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Common Awl Robberfly - Neoitamus cyanurus

and a picture I have used before, of a Kite-tailed Robber Fly Machimus (Tolmerus) atricapillus with a body length of about 20mm.

Kite-tailed Robber Fly - Machimus (Tolmerus) atricapillus

The largest of the family in the UK is the Hornet Robber Fly - Asilus carabroniformis with a body length of about 25mm. Although the abdomen is a bright yellow colour giving it the hornet name, the robber fly is surprisingly well camouflaged, hence the difficult of obtaining a clear picture against its preferred background of cow pats.

Hornet Robberfly - Asilus carabroniformis 

Hornet Robberfly - Asilus carabroniformis

Nowhere near as big at only around 10mm but even creepier looking is this Ferruginous Bee-grabber. They are parasitic, the females will pounce on Bumblebee and Miner Bees depositing an egg into the bees abdomen where it hatches and feeds on its host. They can be found feeding on nectar, this one on bramble, although she? seemed more interested in passing bees than in the nectar.

 Ferruginous Bee-grabber - Sicus ferrugineus

And no blog on beasties of the insect world could go forward without a picture of the dreaded Clegie a member of the Tabanidae family. Robber Flies bite in self defence, bees sting in self defence but clegs bite just for the fun of it and it can be quite painful. To be fair the female needs blood in order to be able develop eggs and the male doesn't bite.

The female injects an anti-coagulant to ensure she can feed freely. You probably also get a dose of Equine infectious anaemia (EIA), also known as swamp fever, which is a viral disease that attacks a horse's immune system. There is no cure and no vaccine for this viral infection, which is caused by a retrovirus closely related to the HIV virus in humans. EIA is often fatal to horses but does not affect humans. Maybe not, but for many of us, something in a cleg bite can cause serious swelling and considerable pain for a few days.

The culprit - or at least one of the culprits.

Band-eyed Brown Horsefly - Tabanus bromius

More beasts than beauties but it's great fun finding and photographing them. Lets hope for a few more before the summer is out.