Key to the Greenbottles (Lucilia) of Europe with some notes on Africa
The genus Lucilia is very difficult to identify from photographs (as are many other genera of blow flies). But the greenbottles are also very commonly observed, and there is a tendency to overidentify certain species (I'm looking at you sericata...). Most people I know are surprised to discover that there are eight species of greenbottle known just from the UK. There are a further three species in the rest of Europe. As a result of this perfect storm, Lucilia observations on iNaturalist are, frankly, a bit of a mess.
The presentation below should give an idea of what it is necessary to photograph in order to have the best chance of getting identifiable pictures. To spell it out:
1) The bristles on the top of the thorax
2) The base of the wing from the front (not the top)
3) The bristles on the middle tibia (the best angle is to look toward the front of the side of the thorax from just a position just back of the middle leg.
4) The space between the eyes (frons).
The key below is primed for use with photographs but, even so, identification will frequently be impossible. Hopefully it will raise awareness and increase people's confidence to tackle the huge and tangled backlog of observations on iNaturalist.
Which brings me to... Africa! As far as I can tell there is only one additional species of Lucilia in Africa: Lucilia infernalis. This species is immediately distinctive because of the extensive and dark infuscation on the leading half of the wing. I do not know much else about it except that it is widespread in the Afrotropical region, but a picture of it can be seen in Figure 5 of this paper. This is more likely to be confused with certain species of Chrysomya - particularly C laxifrons. Chrysomya can be distinguished by the black margins of the tergites, and the wing infuscation is much better defined in those species that have it. I cannot confidently give a list of which European species may also be present in Africa - I know that L cuprina and L. sericata are widespread on the continent, but others may also be present especially in the north. I believe that only those two species are present in Arabia, so there is little risk of Asian species impinging on East Africa.
The Key below covers the European species and also gives information about how to distinguish 'True greenbottles' from lookalikes. Species found in the UK are underlined. The usual caveat applies: I've made this for my own learning and hopefully for the benefit of others, I believe it to be accurate and based on sound sources carefully considered - but I am not an expert, and Calliphoridae are even outside of my normal activities, so bear that in mind.
The species covered are: Lucilia ampullacea, bufonivora, caesar, cuprina, illustris, magnicornis, pilosiventris, regalis, richardsi, sericata and silvarum.
Comentarios
@edanko, @zdanko
Ooh, this is very nice. I especially like slide 4; will be using it as a reference.
Would it be possible to make the circles on the key for slide 4 larger? I am somewhat colorblind and it is difficult for me to distinguish them.
For the Pre-key, could you add something about the color of the parafrontals and occiput? In Lucilia they are white, but in all of the similar ones you mention (except C. mortuorum), those parts are also metallic green. C. mortuorum has the parafrontals half white, half purple, and the occiput appears mostly purple.
First couplet: basicosta character is difficult to see. I would prefer the images to be rotated to be aligned identically (if it isn't too much work).
Second couplet: I think the image should be brightened a bit. A basic line-drawing might work better, at least for the other side.
Third couplet: Not sure if all of those bristle characters are necessary. L. cuprina and sericata are rather easy to distinguish from decent photos.
Other couplets: All seem good; would like drawings or pictures if you are able to, of course.
@zdanko thanks for the feedback - I've made a few changes. Increase the size of the dots on the key and add letter-labels.
The pre-key: I'd say quite a few of the similiars are easiliy interpreted as having white parafacials...
https://www.inaturalist.org/observations/120493574
https://www.inaturalist.org/observations/162988738
https://www.inaturalist.org/observations/161506277
I have already mentioned green parafacials in reference to Neomyia though. I've also added Chrysomya sp to the pre-key.
Brightened couplet 2. I don't fancy rotating the others, but I made one of the circles bigger because it was obscuring the basicosta a bit.
Problem is that surprisingly few of these species seem to have any photos anywhere really, even to base diagrams on...
sericata - cuprina seems to be thought of as a difficult pair over here, but perhaps that's because we never really see it, so the burden of proof is high.
Sorry, I didn't mean parafacials, I meant the area around the ocellar triangle; the upper frons. All of the references that you linked have green there except for the Cynomya.
Ah ok, yeah. I've added that as a negative on Lucilia to catch all, I think it's often hard to see and if people miss it in a positive statement it will send them the wrong way.
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