Two wings are better than four

Two weeks ago I attended the Introduction to Flies course with the British Entomological and Natural History Society (BENHS), at their headquarters at Dinton Pastures Country Park. The centre is a very friendly and encouraging place, with volunteer tutors helping entomologists to improve their microscopy skills, receive guidance and gain confidence in different invertebrate groups.

The specimens room: rows of microscopes on work stations and cabinets line the walls

'Why study flies?' is a question we are asked A LOT when out in the field (members of public initially assume we are catching butterflies). As well as being important pollinators, they perform a wide variety of ecosystem functions. They make up a big part of the foodchain for other wildlife, they help to break down rotting organic matter and contribute to nutrient cycles. Without flies, quite frankly us vertebrates would not be here.

We don't often need to catch butterflies and the other larger 'macroinverts' for identification, as many are doable in the field or with a clear photograph. Also, there is only a small handful of butterfly species to become familiar with (there are 33 at Gatwick). Identification of flies however can be subtle, as they can be very small and are a huge group of insects, with over 7,180 species in the UK vs. just 59 butterflies!

What makes a fly a fly? They are defined by their scientific name Diptera, which means two wings. They would have four, but the rear pair of wings have evolved into halteres; two stick-like organs which are essential for balance and control, arguably making flies the best fliers. 

Dipterist extraordinaires Barbara and John Ismay led the workshop, with excellent introductory presentations aimed at just the right level of detail. We then sat at the microscope stations and each attendee was given a box of specimens, each labelled only with a number. It was up to us to run through the key and attempt to get each one down to a family.

Practicing with keys reinforces familiarity with the important invertebrate charactertics, such as position of eyes, shape of antennae, veination of wings, even the bristles on the legs.

The key to families of Diptera was pretty simple and easy to use. I will share a few of the initial steps below....

Step 1. Is your body plan freaky as heck, or do you basically look like a fly?

Step 2. Are your antennae rather simple and segmented, or highly modified?

Profile shot of a fancy modified antenna

Step 3. What on earth is going on with that crack in your face?

And so on and so forth, until the key comes out at a family name.

Barbara and John run several workshops each year for the Dipterist's Forum, a group dedicated to the study and preservation of flies. They also run a busy consultancy together while volunteering their time to write papers and, of course, identify flies. Considering they are also married, I reckon this pair could have a side-line in writing couple counselling guides.

The BENHS workshops and field meetings are free and run by expert volunteers. If you do manage to get along to one of the sessions then I highly recommend that you sign up for membership to this worthy organisation.

Battling with beetles...

If the ground beetles (Carabidae) are like the European Knights of the 13th century - soldiers encased in ungainly, heavy steel plate armour...

Carabus nemoralis - Goat Meadow at Gatwick

...then the rove beetles (Staphylinidae) are the fearsome Mongolian warriors of the steppes, with overlapping scales of iron and flexible leather, allowing for furiously fast attacks on the enemy (I've been reading a lot of Conn Iggulden historical fiction of late).

Devil's Coach Horse (Ocypus olens) - Photo by W J Heeney

As mortal enemies, Carabids and Staphs will go into battle and the result comes down to the size of beast, which is highly variable. The biggest, baddest of the rove beetles is the Devil's Coach Horse pictured above, which makes Genghis Khan look like a lovable chap who'd give out free hugs.

Last Saturday was the Staphylinidae Identification Workshop with the British Entomological and Natural History Society, lead by Roger Booth and Peter Hodge. It was another excellent day of networking with beginner and expert entomologists alike, learning about the fearsome (and sometimes beautiful) variety of rove beetles.

Roger Booth lead the workshop on Saturday at Dinton Pastures

For me, it was throw back to entomology lessons at Royal Holloway University - Dr Angus was the lecturer who described invertebrate sexual strategy in such graphic detail, that his lectures became infamous (there's even a facebook page in his honour, with one lengthy thread on locust bits which is very NSFW).

A clumsy abdominal dissection

However, I'm not really sure how Dr A. would feel about this; my first attempt since uni at beetle genitalia dissection in order to determine the exact species... Needs a little more practice.

Tergites IX and X, plus one really mashed up aedeagus (male organ)

Aedeagi aside, all beetles at have the same basic body plan. Instead of iron, their exoskeleton is actually made up of a hardened material called chitin, particularly obvious in the solid wing cases (elytra). In Staphylinids, the wings are folded away and the wing case is particularly shortened, allowing for more flexibility in the body.

From Staphylinidae of Britain and Ireland

These are a few I've found about the place so far at Gatwick, usually lurking underneath reptile refugia and bits of bark...

Devil's Coach Horse (Ocypus olens) - a monsterous 30mm

This little bullet-shapped jobby is Tachinus rufipes - around 6mm in length

Drusilla canaliculata (some species names make even adult entomologists snigger), about 5mm

Mongol warriors, about 5ft 7"

Platydracus sp. Another large staph at around 20mm.

Photo by W J Heeney

There is something like 1,000 species of rove beetles in the UK, so lets just say I've got a few more to go! Thanks to Roger and Peter for a brilliant and inspiring workshop.