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Joseph Glatz, age 11, of Grayslake, Illinois, for his question:

What do spiders eat?

All the spiders are born meat eaters, but they do not compete for our precious food supplies. Far from it. Some of their favorite foods are the pesky insects that devour our fruits and vegetables. Some species are especially fond of mosquitoes and the flies that contaminate our foods. When it comes to menus, we should rate the spiders among our most diligent allies.

We share our well populated planet with more than 700,000 different spider species. All of them are carnivorous creatures, yet none of them can chew chunks of solid meat. All their food must be reduced to liquid form. In most cases, the soft insides of their insect victims are partly digested before the juices are sucked down into the spider’s tummy.

All spiders are arthropods, distantly related to the insects and crustaceans. Unlike the insects, they walk on eight rather than six frisky legs. Unlike the insects, their bodies have two rather than three sections. One is the head thorax, the other is the abdomen. Unlike the insects, none of the spiders take to the air on gauzy wings.

However, both spiders and insects have rather elaborate mouth parts, made of paired sections. The average spider has a small round mouth opening, a couple of fierce fangs and a group of sections arranged to form a short tube for sucking. Attached to each fang is a gland that manufactures a poisonous liquid. Black widows, tarantulas and a few of the giant spiders can bite and poison people. But the fangs of most spiders cannot do much harm to human flesh.

Most insects are quicker than most spiders. No doubt this is why the spiders use such clever devices to catch their prey. Most of them spin silken threads and weave silken nets, traps or snares. Some of the threads are coated with goo and when a fly flies into a gauzy web, the more she struggles the more entangled she becomes. Meantime, the hungry spider watches and waits in her shady corner.

When she decides that the fly is safely trapped, the spider strides forth for the kill. Her eight feet step briskly over the same web that stuck to the struggling fly. This is because the spider put goo on only some of the threads—and she takes care to step on the non sticky ones.

The first thing she does when she reaches her victim is to stab in her poisonous fangs. This paralyzes the fly and perhaps puts her out of her misery. Meantime, down in the spider’s intestine, glands are producing special enzymes. These digestive juices are pumped into the fly and her internal organs are reduced to pulp. Now the hungry spider can sip her dinner.

Even young spiderings are carnivorous and sometimes they feed on each other. Some of the giant spiders have a leg span of ten inches and can attack birds and small mammals. Usually a spider liquefies and devours her prey on the spot. But sometimes the victim is wrapped in a silken cocoon and stored for later.

 

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