The most ancient forms of animal life on the earth are the invertebrates. They are also by far the most numerous. With more than 1.5 million known species, it is estimated that 97 percent of all the animal species are invertebrates. Invertebrates exist in a variety of habitats and forms. Some are soft-bodied animals, such as worms or jellyfish, while others, such as insects and crustaceans, have a hard external skeleton for protection. This fascinating group of creatures offers amazing examples of adaptation and habits. Mosquitoes can peirce the skin of mammals and feed on their blood. Flies can eat solid food because their digestive process begins outside their bodies. No human athlete can match the jumping prowess of the tiny wingless flea. Many invertebrates play a vital role in food chains and ecosystems so they are very important to other species. Bees and other pollinating insects are essential to the life cycle of many flowering plants that provide food for humans and other animals. Other invertebrates are useful predators and control. Did you know that there are 35,000 known species of spiders (only 30 are dangerous to people), and that without spiders as expert predators the world might overrun by insect pests?