There are more than 48,000 known species of spiders found in habitats all over the world.

The Goliath birdeater belongs to the tarantula family. It can have a legspan up to 30 cm (12 in), a body length of up to 11.9 cm (4.7 in) and can weigh up to 175 g (6.2 oz). Native to the upland rain forest regions of northern South America, it is part of the local cuisine and is prepared by singeing off the urticating hairs and roasting it in banana leaves. The flavor has been described as "shrimplike".

The earth contains an average of 1 million spiders per acre of land, and that number might be closer to 3 million in the tropics. It is estimated that a human is never more than 10 feet away from a spider. Ever.

According to the Guiness Book of World Records the most poisonous (or venomous) spider in the world is the Brazilian wandering spider (Phoneutria nigriventer) or banana spider. Its venom is so potent that just 0.006 mg (0.00000021 oz) can kill a mouse, making it the most active neurotoxic venom of any known spider.

In humans, oxygen is bound to hemoglobin, a molecule that contains iron and gives blood its red color. In spiders, oxygen is bound to hemocyanin, a molecule that contains copper rather than iron, making their blood blue.

Spider silk is one of the strongest protein fibres in the world. In fact, in terms of tensile strength, which is the maximum amount of stress a material can endure before breaking, spider silk is five times stronger than steel. If it was converted to human size, it would be strong enough to stop a jetliner in its flightpath.

All spiders produce silk but not all spiders spin webs. Silk is used for climbing, to create webs, to build smooth walls in burrows, build egg sacs, and wrap prey.

The Darwin's bark spider (Caerostris darwini) was discovered in Madagascar in 2009. It's hard to understand why nobody noticed these spiders before. A single web can span a river 25 meters wide and the silk is the toughest biological material ever studied, over ten times tougher than a similarly-sized piece of Kevlar.

A study in the journal Biology Letters singled out nursery web spiders Pisaura mirabilis as the species best known for giving "nuptial gifts" from males to females. Male spiders present their female partners with gifts of insects, mostly flies, wrapped up in intricate webs and mating occurs while the female consumes the gift.

Spider webs are rich in vitamin K, which can be effective in clotting blood. Before the use of gauze, some doctors used to put spider webs on wounds.