FACT: Predating the appearance of flies by 100 million years, the spider differs from other insects in that it has a two, rather than a three segmented body and 8 legs. Its silken threads are not only used to weave dazzling webs, they have also served in the past as poultices used to impede blood flow. While some Spiders can be more toxic than others, all Spiders play a vital role in controlling insect populations. In the United States the most venomous spider is the black widow . It's venom is 15 times more lethal than that of a rattlesnake. Marked by a red hourglass shape on its belly, the female has been known to eat the male spider after mating.