Deadly Spiders

Deadly Spiders — page 1 — DEADLY SPIDERS For many of us spiders are fearsome creatures But they’re also fascinating They’ve lived on Earth for more than 300 million years and have evolved to live in almost every dryland habitat from deep caves to deserts to rain forests Many seem quite at home in our houses too There are more than fifty thousand species of all shapes and sizes found worldwide except Antarctica Spiders are not related to insects They have eight not six legs their body is in two not three parts and they don’t have antennae Like insects however spiders are arthropods They have an exoskeleton outer armor that must be molted regularly as the young spider grows to adulthood You can sometimes find the empty molts in their webs All spiders make silk a strong thread that is spun from the spinnerets tiny nozzles at the tip of the abdomen Most spider species have eight eyes but some have six four or even just two 6 A spider’s body has two main parts the cephalothorax supporting the eyes mouthparts and legs and the abdomen containing most of the internal organs Leg IV Spinners Leg III Abdomen Femur Patella Tibia Cephalothorax Metatarsus Tarsus Claw Eyes Leg II Chelicera Palp Leg I There are four pairs of legs numbered I to IV front to back

Deadly Spiders — page 2 — Spiders are predators Some catch their prey in webs some ambush it and still others chase it Spiders can’t eat solid food so most spiders use venom poison to kill or paralyze their prey and turn its insides into a kind of gut soup In some species the venom is so strong it can harm or even kill humans but the majority of spiders cannot hurt us They even help us by killing pests It’s been estimated that the prey eaten each year by all spiders weighs more than the entire human race

Deadly Spiders — page 3 — SILK ORB WEBS Like you I keep my comb handy Cribellum Wheeeeeee Some spiders have a cribellum a rack of extra spinnerets that spins a fine silk that is then combed by the legs to make woolly silk for snaring prey Silk is stretchy and strong and spiders often spin a dragline to catch their fall when they leap or drop from a perch such as a twig I’m not quite finished yet A real team effort Silk is so strong that native peoples in New Guinea once wove it over wooden hoops to make nets for fishing in rivers A textile artist in Madagascar collected gold colored silk from more than one million orb weavers to make a beautiful cape Cool there’s my runway marked out I’m coming in to land Stabilimenta are silken zigzags that some spiders weave into their webs Do these eye-catching designs help attract insect prey by reflecting ultraviolet light or do they keep birds away by making the web more visible Do they help to make the spider look bigger Experts aren’t quite sure 8

Deadly Spiders — page 4 — MAKING SILK Stored as a liquid spider silk dries into a thread after being squeezed out of a spider’s spinnerets Spiders can spin different kinds of silk sticky for trapping prey non-sticky for walking on extra strong for hanging from and so on Their most famous creation is the beautiful spiraling orb web but many spiders build more messy-looking three-dimensional tangle webs GOLDEN ORB WEB SPIDER FAMILY NEPHILIDAE Body size female up to 2 inches 50 millimeters male 0 2 0 3 inches 5 8 mm Where found North Central and South America STRONG STUFF Spider silk is five times stronger than steel of the same thickness One day spider silk may be used to make bullet-proof vests for soldiers GARDEN SPIDERS A garden spider may use up to 197 feet 60 meters of silk in a typical orb web but can usually finish the task within an hour

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