A student in Gregg Thompson's sixth-grade social studies class at Woodland Middle School in Gurnee asked, "If humans can see perfectly fine with two eyes, then why do flies or spiders need more than two?"
"There are lots of different eye arrangements in the animal kingdom," said Doug Taron, curator of biology at the Peggy Notebaert Nature Museum in Chicago. The shape and placement of the eye is an indication of how eyes are used to elude or capture prey.
"It's not just the number of eyes that's very different in some creatures; it's where they are on the head," Taron said.
These tiny insects can see you coming. It's no wonder flies are so difficult to shoo. Most flies have as many as seven eyes, one set of compound eyes and five simple eyes. The compound eyes have multiple lenses so they see in a mosaic pattern with very high resolution, giving them the edge on seeing fast movement. Simple eyes have only one lens, like human eyes.
"Given the shape of their eyes, they have a much wider field of view," Taron said.
The buzz on spiders is that they can have any number of eyes or no eyes at all. There are two-eyed, four-eyed, six-eyed, eight-eyed and no-eyed spiders. Jumping spiders, like most spider types, fall in to the eight-eyed category. Their eyes have a four-layer retina with telephoto-lens accuracy.
"Jumping spiders sneak up and jump. They need to see at a distance and close up," Taron said.
Color is another aspect of vision. "Colorful organisms frequently have good color vision," Taron said. "Some see no color and others see colors that we can't see. Bees can see further into the ultraviolet spectrum than we can."
Want to see a spider? The "Extreme Greenhouse" exhibit at the Peggy Notebaert Nature Museum has some on display. The museum is most famous for its Judy Istock Butterfly Haven, a lush tropical respite and home to nearly 1,000 butterflies and some colorful birds. Don't miss the museum's special Monarch Butterfly exhibit in honor of the Chicago-wide "Mexico 2010" sponsored by the Mexican Consulate, through Aug. 30.
The museum is open Monday through Friday 9 a.m. to 4:30 p.m., and weekends 10 a.m. to 5 p.m. Admission is $9 for adults, $7 for students and seniors and $3 for children 3 to 12. The museum is located at 2340 N. Cannon Drive, across from Lincoln Park Zoo.
Check these out
The Grayslake Area Public Library suggests these book titles on insect eyes:
• "Eyes," by Sara Swan Miller
• "Insect," by Laurence Mound
• "Bug Faces," by Darlyne A. Murawski
• "Insects & Spiders," by David Burnie
• "Super-Size Bugs," by Andrew Davies