A blog about birds, insects, in fact any kind of wildlife. Mostly around Topsham, Devon. Photos, sketches and illustrations.

Sunday, 21 February 2010

Six Green Bottles...



Few flies have common, English names, but most people know about bluebottles and greenbottles? I’m happy to say that things are a little more interesting than that.

Anyone who takes up photographing insects soon notices the bright, metallic green flies which seem to be everywhere in the warmer months. Many of the popular books or websites will have photos, often confidently labelled Lucilia caesar. However, things aren’t necessarily what they seem. There are quite a few similar species, there are also several species of Lucilia to consider.

The photos show some of the commoner ones – or at least the species I’ve managed to photograph.









There’s a very nice key to these lookalikes in Colyer & Hammond’s Flies of the British Isles (highly recommended, by the way, though out of print). Here’s my updated version, modernising names, terminology etc. :

1.Frons and jowls metallic-green..........................Neomyia
Frons and jowls not metallic-green....................................2

2.Medial vein bowed or curved towards vein R4+5,
not sharply bent......................................................Eudasyphora
Medial vein sharply bent towards vein R4+5...................3

3.Eyes hairy; discals present on abdomen;
abdominal bristles stout..................................Gymnocheta viridis
Eyes bare; discals absent;
abdominal bristles generally weak.....................................4

4.Face and jowls yellow...............................Cynomya mortuorum
Face and jowls not yellow...........................................Lucilia spp.

Some explanations may be needed:

Frons and jowls – forehead and lower part of the cheek.

Medial vein and vein R4+5 – on these flies, the two wing veins which approach each other at the wing-tip; the medial vein is the one at the front, vein R4+5 is the one behind – the one that curves or bends forward.

Discals – bristles (often stout) in the middle of an abdominal segment.

Some of these species are actually a good deal easier in the field than it might appear from the key.

Cynomya mortuorum - quite a large blowfly (similar in size and shape to a Bluebottle Calliphora) with a deep yellowish face. Not very common in my experience.

Gymnocheta viridis – A Tachinid or parasite fly. Bristly and small headed and quite unlike the other ‘greenbottles’.

Eudasyphora spp. – the curved, not sharply bent, medial vein is a very good character and fairly easily seen.

Neomyia spp. – the green forehead is fairly easy to see if the head is seen close from the front; there is a nice clear contrast between the forehead (metallic green) and the parafacial area (whitish).

Lucilia spp. – face/forehead not metallic green or bright yellow, not particularly bristly and a sharply bent medial vein. In my experience the great majority of Greenbottles are Lucilia spp. There are seven species of Lucilia on the British list and that’s where things get a little tricky.

Ok, I know there are seven flies shown above - I added another photo and forgot to change the title.

To be continued...

Refs. Colyer & Hammond; Flies of The Brish Isles 2nd edition, 1968

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