By controlling insect population sizes, they keep most potential insect populations too small to be economically damaging, most of the time. For this reason, the importance of spiders to agriculture has generally been underestimated. Spiders also eat many insects that bother humans, such as mosquitoes and cockroaches. Since a single spider may eat many mosquitoes in one day, over the course of its lifetime a spider may prevent hundreds of mosquitoes from surviving to produce even more mosquito offspring. Additionally, spiders are an important food source for birds, lizards, wasps and other animals.
Many people fear spiders, but actually the majority of spiders are too small to bite humans.
Any spider smaller than about 8 mm, or one-quarter inch, in body length cannot break human skin with their tiny fangs, and most spider species are smaller than this. Of those spiders large enough to bite humans, only a few have bites which are dangerous to humans. Spider Silk Many types of spiders construct specific types of silken web to trap prey. These come in a variety of forms, from the familiar orb web and cobweb to sheets, funnels, tubes, ladders, and even a single thread. A single spider may produce more than a half-dozen different kinds of silk for different purposes, some sticky, some not.