Spiders are incredibly diverse, with around 40,000 different species worldwide. Some spiders roam across the ground actively hunting for prey, while others construct complex webs to capture anything unfortunate enough to fly, jump or fall into them.
Researchers at the Urban Wildlife Institute often encounter spiders in the grass or on trees at Nature Boardwalk at Lincoln Park Zoo. During the recent summer months, though, we’ve noticed some of them—such as the grass spider pictured below—making homes in the metal security cases housing our motion-triggered wildlife cameras!
Grass spiders weave sheet-like webs that generally have a small funnel in a corner for them to hide. The web itself is not sticky, so when unsuspecting prey make contact with it the spider charges out and attempts to paralyze them with its venom. We actually interrupted this individual snacking on an earwig when we cracked open the camera case to check its batteries.
While many people run away in fear or roll up newspapers at the sight of spiders, we’ve recently become very interested in their biology and how important they are to ecosystems like Nature Boardwalk.
Consider, for example, the manner in which spiders breathe.
Most spiders have structures called book lungs, which act as their respiration organ. Even though they’re called lungs, they’re very different from our own. Located inside spiders’ abdomens, book lungs resemble a collection of plates and are filled with the spider’s blood (called hemolymph).
Spiders open small valves, called spiracles, on the undersides of their bodies to deliver oxygen to the book lungs. The oxygen then flows into small, copper-rich proteins present in the hemolymph located in the book lungs’ plates. Interestingly, it’s this particular protein that gives spiders’ hemolymph its characteristic bluish-green hue.
If you can get past your arachnophobia, take a look around Nature Boardwalk to see if you can spot any of these tiny predators. You may find they’ve got a leg—or two or eight—up on the competition.
Mason Fidino is coordinator of wildlife management in Lincoln Park Zoo's Urban Wildlife Institute.