OCTOBER
2011

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

10-27-11

Download the audio of On Six Legs: MP3, WMV.

Friends of Spiders
Please Stand Up


Most people don't harbor fond feelings for the creatures known as spiders. In fact, as a group, spiders are probably the least-liked of all arthropods. And that is saying something. None of the other common arthropods - insects, ticks, mites, scorpions, lobsters, crayfish and pillbugs - rank very high on the human likeability scale either.

When it comes to fondness for other animals we humans are partial to creatures that are more like us. You know, warm-blooded and hairy. We love these kinds of animals and even keep some, such as dogs, cats, and the occasional rat, as pets. We spend all kinds of money on our mammal pets, providing fancy food, veterinary care, special toys and even grooming.
 
We also like birds. Some of these fine-feathered creatures occupy favored perches as human pets. As we do with our mammal pets, we are willing to put our money where our attitude lies. Anybody purchased a birdhouse or birdseed lately?

On the other hand, arthropods are cold-blooded, have a hard exoskeleton and don't come when you call, roll over on command, or like to be petted. These joint-legged creatures are small and that makes them hard to see well. Consequently, we begin to imagine things that we can't see with our own eyes. And, worst of all, some arthropod species add human injury to insult by biting, stinging and transmitting diseases.

So for most people insects or spiders are the big number-one on their "animals I don't like" list. And in my experience spiders have the rather dubious honor of topping such a list more often than insects.

Spiders and insects share many structural characteristics. However spiders are different from insects in that they appear to have two body sections rather than three, have eight legs rather than six and lack antennae.

In the United States, some 3,000 species of spiders have been given scientific names. Spiders live in all kinds of habitats and all prey on insects. So if you don't like having insects around, you've got to love spiders. So how do spiders catch their prey? Common names of spiders sometimes will tell that story.

Most people are familiar with spider webs. All spiders have the ability to produce silk, and many species use the material to construct their namesake traps to capture insect prey. Orb weaver spiders produce what most people recognize as a spider web consisting of support lines with the connecting strands spiraling outward from the center. The large black-and-yellow garden spider that hangs upside down on the web is an orb weaver. This is one of the larger spiders in the United States, and it has the interesting habit of eating the remains of the web and building a new one each night.

Other spiders that use silk to capture prey include the funnel web weavers. These spiders produce a characteristic funnel from silk. The funnel leads to the lair of the spider. At the front of the funnel is a barrier that serves to knock flying insects onto the funnel where the waiting spider captures the prey.

The American house spider also produces webs. This spider lives in corners of houses and barns where their webs not only catch insects but also dust. These are the cobwebs that are the inspiration for the common Halloween decorations and the bane of homeowners.

The other major group of spiders is called hunting spiders. These spiders capture their prey without the use of silk, and some have names suggestive of hunters: wolf spiders, fishing spiders, lynx spiders and huntsman spiders, to name a few.

Hunting spiders include some of the largest spiders - the tarantulas. While some tarantulas have a dangerous bite, those living in the Southwest have a bite no more dangerous than a bee sting. Because of their size, these spiders sometimes feed on other small animals, including lizards. One very large tarantula is called a bird eater because it will catch and eat small birds.

All spiders have poison glands and a pair of fangs, called chelicerae, through which poison is delivered to prey. The fangs can also be used for a defensive bite. But spider bites to humans are rare - we're much too big to be a food item for an itsy bitsy spider!   

 

Writer: Tom Turpin
Editor: Olivia Maddox