We classify spiders as arachnids, which include over 60,000 species of animals. ¹⁾

There are over 49,800 described species of spiders divided into 129 families. ²⁾

The body of spiders is made up of two segments. These are the cephalothorax and abdomen, which are joined by the styli. In front of the cephalothorax are the maxillae and behind them are the cephalothoraxes. These are followed by the crotch legs. ³⁾

The smallest is the Patu digua species native to Colombia, which has a body 0.015 inches long. ⁴⁾

The largest spiders are tarantulas, and the goliath birdeater is the biggest of them all. Its body size can reach up to about 5 inches, and if you add its leg span it measures up to 11 inches and weighs up to 6 ounces. ⁵⁾

If there are any protuberances on the abdomen of a spider, they are the preputial glands. ⁶⁾

Spider silk can be used not only to build webs but also to carry sperm, build cocoons for eggs, wrap prey and even build balloons/parachutes so they can fly. ⁷⁾

Each spider leg is made up of seven segments (starting with the body, these are the coxa, trochanter, femur, patella, tibia, metatarsus, and tarsus). ⁸⁾

In most spiders, vision is not particularly well developed. ⁹⁾

To locate prey, some spiders use environmental vibrations. This is common, especially among web-weaving spiders. Some species can also locate prey by detecting changes in air pressure. ¹⁰⁾

The eyes of spiders of the genus Deinopis have phenomenal properties by spider standards. To date, 51 species of these spiders have been described. ¹¹⁾

The blood circulatory system of spiders is open. This means they have no veins, but the hemolymph is forced through arteries into the body cavities (hemocoels) surrounding the internal organs. ¹²⁾

Spiders breathe with the help of lung tubes or tracheae. ¹³⁾

Bagheera kiplingi are spiders whose diet is 90% plant-based. ¹⁴⁾

There are spiders that do not have venom glands at all, these include spiders in the family Uloboridae. ¹⁵⁾

Work is underway to use the venom of certain spiders to create an organic pesticide. Such a toxin would be able to protect crops from harmful insects without polluting the environment. ¹⁶⁾

Spiders are not capable of biting their prey. In most, the mouth apparatus is equipped with a straw-like device that allows the spider to drink the dissolved tissues of its prey. ¹⁷⁾

Female spiders are capable of laying up to 3,000 eggs. ¹⁸⁾