Araneae

Araneae is an order of arachnids that comprises the spiders. Spiders are characterized by their eight legs, chelicerae with fangs that inject venom, and the ability to spin silk. They are found worldwide on every continent except for Antarctica.

Anatomy

Spiders have two main body segments: the cephalothorax and the abdomen. The cephalothorax, also known as the prosoma, houses the eyes, mouthparts, and legs. The abdomen, or opisthosoma, contains the digestive and reproductive organs, as well as the silk-producing spinnerets.

Eyes

Most spiders have eight eyes, although some species have fewer. The arrangement and number of eyes can be used to identify different spider families.

Silk Production

Spiders produce silk from specialized glands located in their abdomen. The silk is used for various purposes, including building webs, creating egg sacs, and wrapping prey.

Behavior

Spiders exhibit a wide range of behaviors, from the solitary and sedentary to the highly social and active. Many spiders are known for their intricate webs, which they use to capture prey. Others are active hunters that do not rely on webs.

Webs

Web-building spiders create various types of webs, including orb webs, funnel webs, and sheet webs. The design of the web is often specific to the spider's family and can be used for identification.

Venom

All spiders possess venom, which they use to subdue their prey. While most spider venom is harmless to humans, a few species, such as the black widow and the brown recluse, have venom that can cause significant medical issues.

Reproduction

Spiders reproduce sexually, with males often performing elaborate courtship rituals to attract females. After mating, females lay eggs, which they often encase in silk sacs. The number of eggs and the care provided to the offspring vary widely among species.

Classification

The order Araneae is divided into two suborders: Mesothelae and Opisthothelae. The latter is further divided into the infraorders Mygalomorphae and Araneomorphae.

Mesothelae

Mesothelae spiders are considered the most primitive, with segmented abdomens and other ancestral traits.

Opisthothelae

Opisthothelae spiders include the majority of modern spiders. This suborder is divided into two infraorders:

• Mygalomorphae: Includes tarantulas and trapdoor spiders.
• Araneomorphae: The largest infraorder, containing most of the common spiders.

Ecology

Spiders play a crucial role in ecosystems as both predators and prey. They help control insect populations and serve as food for various animals, including birds and other arthropods.

Related Pages

• Arachnid
• Web (spider)
• Venom
• Silk
• Black widow spider
• Brown recluse spider