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Index of Subjects James: Thanks for picking this up, interesting pics. I think he is mostly using a nice macro lens and a double gooseneck lamp shining obliquely from the top of the shot (you can see two reflections at the top of the eyes in several places), but the water droplets are something else, not 'natural'. You don't usually find the heads of live flies in nature covered in multiple fine water droplets. As mentioned recently, a way to immobilize an insect is to put it in a pill vial in the freezer for some minutes, then take it out and shoot a few pictures as warms up, alive. The penalty is that if you let it warm up in conditions of high humidity, like recent weeks, water droplets will condense on the cold surfaces from water vapour in the air, spoiling the picture (one view) or giving it a more 'artistic' appeal (perhaps another view). About 2/3 of the pictures show condensation droplets like this, but more extreme. My guess is that the photographer captures the insects and kills them in the freezer so they are then equilibrated, really cold at -15°C, then warms them up again in the open to photograph them. If instead he'd let them warm up for ~10 minutes in a new, closed pill vial, containing some crystals of dehydrated Silica Gel or Drierite or other agent that aggressively absorbs water from the air, condensation shouldn't happen. That most of the flies and the grasshopper are dead and that the inside of the eye is damaged, presumably by freeze-thawing, is suggested by the observation that a 'pseudopupil' is not visible in any of the eyes, as it normally is in most live insects under such conditions of illumination. The pseudopupil is a local dark zone where the eye faces directly to the camera. Light entering from that direction fails to come back out again to the camera because it gets absorbed by the visual pigment (xanthopsin) plus the screening pigments just to the sides of this (2 types of these); elsewhere, for most of the eye, light bounces more obliquely off surfaces and comes back out again, so it looks brighter there. If the insect is rotated, the pseudopupil follows, moving across the eye accordingly. The depth of field of the corneal lens is both very precisely located and only about 2 micrometers deep (2 x 10^-6 meters). Freezing destroys this precision by ice crystal damage, the eye doesn't recover, goes out of focus and the pseudopupil disappears. This pseudopupil summary doesn't apply at all to some flies (e.g. tabanids and dolichopodids) and perhaps to shiny hymenopterans, where powerful reflector filters actually in the cornea itself (the outermost layer) reflect too much light back out superficially, so you cannot see deeper into the eye. The deer fly pic is a case in point. Identification of flies hinges on a number of characters, with wing structure/venation and antennal structure being among the most important, also bristle patterns. Sometimes head/eye structure is suggestive, for instance for dolichpodids, but just taking photos of the head by itself is usually not useful for a positive ID even to family level, never mind to species levels. So I'd guess that (10) is probably a male syrphid, (7) might be a calliphorid/muscid/anthomyid, and (9) is probably an acaylptrate like a dryomyzid, but these guesses could be way off. Steve (Hfx) ________________________________________ From: naturens-owner@chebucto.ns.ca [naturens-owner@chebucto.ns.ca] on behalf of James Churchill [jameslchurchill@gmail.com] Sent: Thursday, August 14, 2014 1:04 PM To: naturens Subject: [NatureNS] Paul Illsley's fantastic macros of inverts In case you have not seen these amazing images (below) No doubt he is using some kind of creative techniques. He is also seeking help with some identifications: http://www.paulillsley.com/Tiny_Faces/ cheers, -- James Churchill Kentville, Nova Scotia jameslchurchill@gmail.com<mailto:jameslchurchill@gmail.com> (902) 681-2374
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