Relevant to the last meeting, a few comments on insect eyes & vision.
You’ll note some interesting features in Gary Powell’s nice photo of katydid eyes.
First, the dark spots that seem to be looking at you. They are! These are the simple eyes that are pointed directly at you, forming dark patches known as pseudopupils. You’re looking straight into the light receptive photopigments, and these spots will follow you with changing position relative to the insect- just like Mona Lisa.
Second, the green color of the eyes, which in this case, varies a bit over the surface. These pigments are in the cells between the simple eyes, acting to block light transfer between the individual eye segments. An insect lacking these pigments will show reduced spatial actuity. In fruit flies, we can generate flies lacking these pigments, and yes, it is possible to do behavioral tests of spatial acuity with fruit flies.
What does the world look like to an insect? Most if not all insects have poor vision in the long wavelengths, the red part of the spectrum. Hence, bug lights that are yellow or red. So from the insect’s point of view, red parts of the visual field will look black. But they make up for this deficit with the ability to see in the ultraviolet & to detect polarization of light across the sky.
For the most amazing arthropod eyes, check out the mantis shrimp- they’re looking at prey with multiple parts of their eyes, using far more visual photopigments than we have:
http://phys.org/news/2013-09-mantis-shrimp-world-eyesbut.html
Jay Hirsh
