Characteristics of Spiders

Characteristics of Spiders Spiders are the largest entirely carnivorous group of animals on the planet. Without spiders, insects would reach pest proportions throughout the entire world. A spiders looks, preferred foods, and prey-capturing skills set it apart from other arachnids. What Do Spiders Look Like? Spiders are not insects. Like insects and crustaceans, they belong to a subgroup  within the phylum arthropod, which means they are invertebrates and have an exoskeleton. Spiders belong to the  class Arachnida. Like all arachnids, spiders have just two body regions, a cephalothorax, and an abdomen. In spiders, these two body regions join at a narrow waist, called a pedicel. The abdomen is soft and unsegmented, while the cephalothorax is harder and includes the eight legs that spiders are known for. Most spiders have eight simple eyes, although some have less or even none at all. Not all arachnids are spiders. Spiders belong to the order Araneae.  Scorpions and daddy longlegs, which are usually confused for spiders, belong to different orders. Preferred Food Spiders prey on other organisms, usually insects. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing  it with sticky balls, mimicking the prey to avoid detection or running it down. Most detect prey mainly by sensing vibrations, but active hunters have acute vision. Spiders can only consume liquids, as they lack chewing mouthparts. They use chelicerae, pointed appendages, like fangs at the front of the cephalothorax, to grasp prey and inject venom. Digestive juices break down the food into liquid, which can be ingested by the spider. Web-Making Silk All spiders make silk. Usually, the spinnerets that make the silk are under the tip of the abdomen, allowing them to spin a long strand of silk behind them. Spider Habitat More than 40,000 species of spiders inhabit the earth. They are found on every continent except for Antarctica and have become established in nearly every habitat, with the exceptions of air and sea colonization. They have been found in the Arctic as well. The vast majority of spiders are terrestrial, although a few specialized species live in fresh water. Common Spiders Some of the most common spiders include: Orb weavers, known for weaving large, circular websCobweb spiders, including the venomous black widowWolf spiders,  large spiders that hunt at nightTarantulas, huge, hairy hunting spidersJumping spiders,  tiny spiders with big eyes and bigger personalities Interesting Spiders There are some spiders that have interesting features that set them apart. Female flower crab spiders, also known as Misumena vatia, change colors from white to yellow to match flowers, where they lie in wait for pollinators to eat. Spiders of the genus Celaenia resemble bird droppings, a clever camouflage that keeps them safe from most predators. The ant spiders of the family Zodariidae are so named because they mimic ants. Some use their front legs to mimic antennae. The magnificent spider, so called the Ordgarius magnificus, tricks its moth prey by setting a silk trap with a pheromone. The pheromone mimics a moths reproductive hormones, which lures male moths with the prospect of a female.   Sources: Insects: Their Natural History and Diversity, by Stephen O. Marshall