Compound Eyes
are COOL! Insect eyes are not like ours at all. Well, they
are like ours in that they see things, and they use pigments to help them
perceive colors, but that's about where the similarities stop. If you look
at a dragonfly or a house fly (or P.R. Mantis), it looks like it
has two eyes. But really each of those eyes is made of hundreds - sometimes
thousands - of small eyes! Each of these eyes is shaped like a
hexagon
(a six-sided shape). They each have a separate nerve which takes a picture
to the insect's brain.
The dragonfly you see here has about 2000 little eyes in each compound
eye. That means it has over 4000 different pictures going into its brain
at any one time! Imagine! And its brain is tiny.
A Demonstration You Can Do
How many pictures do we get into our brains?
To demonstrate the answer to this question, put your finger up about a foot away in front of your face. Look at the side of your finger. Now wink one eye. Then, while still looking at your finger, wink the other eye. Do this a few times and you will notice your finger "moving" in front of your face. Now do it again and just focus on your fingernail. When you look at it out of each eye, it gets bigger and smaller. In this case, you are actually seeing your fingernail from two different angles!
So, while our dragonfly friend has to figure out around 4,000 pictures with its tiny, little brain, we only have to work on two! Obviously, our brain's are much bigger than a dragonfly's. And we only get two pictures into our brain at one time. It looks to us like we only get one picture because our brains know how to put them together and make things look 3-D.
That leaves us with the question, "What does a
dragonfly see?" Who knows!!? Perhaps you've seen the Far Side
cartoon by Gary
Larson that has the caption, "The last thing a fly sees." The frame
is filled with hexagons and in each one is a fat lady with a fly swatter!
That's the way many entomologists believe bugs see. Visit the B-Eye
to see an interesting effort to demonstrate the way a bee sees. It seems
just as likely that their brains do the same thing ours do and put all
the images together into one. Scientists might figure it out one day, but
it's hard to imagine how they will do it!
1998 - Mark Berman, BUGMAN Educational Entoprises