Spiders belong to the class Arachnida, which also includes scorpions and dust mites. Arachnids are not insects. They have four pairs of legs, unlike insects, which have three. Furthermore, their body is divided in two parts, not three. More than 400 million years ago, arachnids were among the first animals to leave the ocean and venture onto dry land.
Spiders have special glands on their abdomen that secrete silk. This allows them to make webs, which they use to capture their prey. Many spiders build spiral-shaped webs, others weave traps that look like containers, and some spin “lassos” that they throw over their prey. Besides silk glands, spiders are also equipped with venom glands. These are located in the chelicerae, which are small hooks attached to the head. A spider’s venom, which is rarely fatal to humans, helps it kill or paralyze small prey before eating it.
The bolas spider captures male moths using a technique usually associated with the most skillful cowboys! Its snare is a thread 5 centimeters (2 inches) long with a sticky ball on the end. The spider makes the ball from a substance that smells like the odor given off by female moths when they are ready to mate. By twirling this lasso with one of its legs, the spider intercepts and entangles the male moths attracted by the irresistible odor of their false lady-love.
Most spiders are solitary. Among the thousands of known species, however, there are a few dozen that live in groups. These social spiders, as they are called, combine their efforts to weave gigantic webs that can stretch the length of a football field. These social spiders form colonies that are made up of thousands of individuals. With the help of their giant webs, social spiders can capture insects 10 times their size!
Despite being ingenious weavers, clever hunters, and amazing acrobats, spiders are unfortunately disliked by most humans. And yet, they perform a valuable service by eating large quantities of pests. In fact, spiders are extremely important to the ecological balance of the planet!