Spiders are arachnids, meaning they have eight legs and no wings. They are also carnivorous, meaning they primarily eat other insects. Spiders come in a variety of shapes and sizes, but all spider anatomy is based on the same basic body plan. This guide will teach you everything you need to know about spider anatomy, spider behavior, and how to identify common household spiders based on their anatomical features.
All spiders have three main body parts: the cephalothorax, abdomen, and pedipalps. The cephalothorax is fused together from the spider's head and thorax, and it houses the spider's eyes, fangs, and mouthparts. The abdomen is the spider's large, bulbous back end, and it contains most of the spider's internal organs. The pedipalps are small, leg-like appendages near the spider's mouth that it uses to grasp prey.
Spiders also have two main types of legs: walking legs and spinning legs. Walking legs are longer and thinner than spinning legs, and they are used for walking and jumping. Spinning legs are shorter and thicker than walking legs, and they are used for spinning webs.
Spiders spin webs by releasing a sticky silk from their spinning legs. This silk hardens when it comes into contact with air, creating a strong, flexible web that spider can use to catch prey. They create the silk by ingesting liquid silk from their spinning glands and then extruding it through small holes in their mouths.
Most spiders are nocturnal hunters, meaning they prefer to hunt at night. During the day, they hide in dark places like cracks in walls or under furniture. When a spider feels threatened, it will usually try to run away first. If it can't escape, it will defend itself by biting the threat with its venomous fangs.
Most spider bites are not dangerous to humans, but some spider species have venom that can cause serious health problems in people. The two most common poisonous spider species in the United States are the black widow spider and the brown recluse spider.
The best way to identify a spider is to look at its anatomical features. Here are some of the most common household spiders and how to identify them based on their anatomy:
Wolf spider: This spider has a gray or brown body with a large, round abdomen. It is about ½ to ⅔ inch long.
Daddy Long Legs: This spider has a small, round body with extremely long legs (hence the name). It is about ¼ inch long.
Common house spider: This spider has a brown or gray body with long, spindly legs. It is about ¼ inch long.
Black widow spider: This spider has a shiny black body with a red hourglass shape on its abdomen. It is about ½ inch long. These spiders are particularly dangerous, but fortunately, they are relatively uncommon in residential areas.
Brown recluse spider: This spider has a brown body with a dark violin shape on its back. It is about ¼ inch long. Like the black widow, these spiders are also dangerous, but uncommon in or near homes.
Now that you know all about spider anatomy and behavior, you should be able to identify any spider you come across in your home. Spiders are generally harmless to humans, but there are a few species whose venom can cause serious health problems. To learn about common spiders in Washington state, check out our article here.
If you ever see a spider that you can't identify, it's best to err on the side of caution and call a pest control professional to remove it from your home. Just remember to be careful when handling them, and always consult a doctor if you think you've been bitten by a poisonous spider. Happy hunting!
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