Ask An Entomologist: Insect Vision
May 9th, 2007 by Kelley
Dave
I’m wondering if there’s any way of knowing how many images a compound-eyed insect receives. (I’m reminded of the Far Side cartoon in which “the last thing a bug ever sees” is an entire panel of the same image, broken into tessellating diamonds: a woman holding a fly swatter.)
I’m very curious. Please answer using layman-speak, if there is an answer.
Insects’ compound eyes, in general, bulge out on either side of their head. This increases their field of vision on practically all directions. I think I read or heard somewhere that water boatman (an aquatic beetle) can see something like 245 degrees in the horizontal plane and 360 degrees in the vertical plane. The classic theory on insect vision is called the mosaic theory and it suggests that each cell (ommatidia) forms an image of the limited part of the visual field. So, in layman speak, each cell puts together a part of the picture to form the entire object.
You can see a previous post on the insect eye if you want a little more info.
Kelly,
Are you saying each ommatidia forms an “image” on the sensory cells? That would be a tall order for such a simple optical arrangement. I’m pretty sure an ommatidia can merely gather and channel light to these cells. So each ommatidia would contribute a single “pixel” of a relatively low resolution image compiled in the brain from all the pixels sensed together. There is also some sensory crosstalk among adjacent ommatidia that would help smooth out the transitions between pixels. Interestingly the modern ccd and cmos sensors in the best digital cameras use this technique to limit pixelation in the images they produce.