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Index of Subjects Hi Steve Thank you for this info. I take it the hexagonal facets in the lower eye are mainly useful to detect movement as in other insects? I read something about Mayflies having a dual function eye but it said nothing more so your explanation really helps. Nancy On Sat, Jul 27, 2013 at 7:43 PM, Stephen R. Shaw <srshaw@dal.ca> wrote: > Your pic is nice but not high enough magnification to see the detailed > structure of the eyes, even more alien-looking than you may think. > > At least in some male mayflies, the eye is conspicuously bi-lobed, with the > upper half optically quite different than the lower half and probably > specialized for spotting females (this has been studied in other insects, > mostly flies). > > The facets in the upper eye in some mayflies are square, not hexagonal as > they are in the lenses of the lower eye. Square facets in other arthropods > (crustaceans) have reflecting layers inside, lining their square optical > tubes, and behave like 2-Dimensional retroreflectors to focus light usefully > inside the eye into a single image. The mayfly's upper eye therefore > possibly may work similarly. The biological structures are somewhat > analogous to the retroreflectors left on the moon by astronauts. The moon > ones have been used to reflect back laser pulses aimed from earth, allowing > for instance the earth-moon distance to be monitored sensitively. > Steve > > Quoting nancy dowd <nancypdowd@gmail.com>: > >> I guess I never really looked closely enough at a mayfly to notice the >> prominent (almost alien looking) eyes: >> http://www.flickr.com/photos/92981528@N08/9367703219/ >> >> This one has its tail filaments snagged in a spider web. I freed it >> and it flew off. Any ID corrections are welcome. >> >> Nancy >> >> > >
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