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Nick, I couldn't agree more. I don't collect and I have no intention of starting, but that's just a matter of time, space and my primary interest being photography. I'm glad that some people do and I'm happy to pass on any interesting specimens that come my way.

As you say, one of the problems with photo-identification (apart from the technical difficulty) is getting the right shots - you get all the angles, pin sharp, but that critical bristle on the hind femur is always hidden. Of course you'll know where to look the next time you see it. Keys are, of course priceless, but I find that they're of most use if you know approximately which genus you're dealing with. The characters used to determine family, subfamily and genus are often the trickiest to see, although often they can be recognised 'provisionally' just on their general appearance. The experts of course, recognise their own groups because they know them so well, and I assume that they're not running them through a key each time. I wonder if the situation is in any way analogous to bird identification early in the 20th Century. Field ID of many species was considered impossible, you had to have a specimen to key out. Now, with all the usual caveats, I wonder if we can't push insect identification a little in that direction. Perhaps it's not just about checking the characters in the keys, maybe there are others not mentioned that could be used.

I detect a certain disdain in some quarters from 'proper' entomologists (no-one on this site, I hasten to add) towards this approach. I think it's vital to not try to push things too far, clearly only 100% certain determinations should be submitted to recorders. But as you say, there's a lot of distributional data to be had from photographers, it may not be the same as specimens but it's better than no data. Like you, I've been thinking about this subject for a while and, rather than rambling on here, I think it's better consigned to my blog.

BTW I don't know whether you've tackled any Tachinids yet but I strongly recommend them. There's a couple of really useful keys; the RES key by Belshaw is still in print (about £20 I think) and You might ask Chris Raper for a copy of his translation of Tschorsnig and Herting's Central European Key. There's always a lot of helpful expert advice here and Tachinids are really smart flies.

Tim