All spiders have fangs. While most spiders have poison glands, only 6 kinds of North American spiders produce venom that is harmful to humans.These 6 spiders are: the black widow, the brown widow, the red-legged widow, the varied widow, the sac spider, and the brown recluse spider. Only female spiders bite.
Spiders are helpful to humans because they eat insects that are harmful to man.For example, spiders eat mosquitoes and flies that carry diseases, and they eat locusts and grasshoppers that destroy crops.
Spiders have been known to eat fish, tadpoles, and small animals.
The body of a spider has 2 main parts: the cephalothorax, which combines the head and the thorax,and the abdomen. A spider has eyes- usually 8 of them located on the frontof its head. The spider's mouth is located under its eyes. The spider has straw-like devices located in its mouth through which the spider can suck thebody fluid from its victims. The spider has a pair of chelicarae which are appendagesthe spider uses to seize its prey. Spiders have a pair of pedipalpi which resemble legs on each side of the spider's mouth. The spider has spinnerets which are fingerlike organs locatedat the rear of the abdomen which spin silk.
The spider's respiratory system consists of tracheae and block lungs.
When male spiders mature, they seek mates. Female spiders have been known to mistakemale spiders for prey and kill them (spiders also eat other spiders). Following mating,female spiders store sperm. Later, females lay more than 2,000 eggs. Most varieties of spiders enclose eggs in a silken egg sac.