Introduction || Spiders


Class Arachnida

Roughly 30000 species of spiders were found. Spiders' head and thorax are coalesced into cephalothorax, and an abdomen has segments united without visible separation. Abdomen and cephalothorax are jointed with slender pedicle. The cephalothorax has four pairs of legs. Venom gland ducts open at the chelicera ends.

The abdomen has 1-4 pairs of spinnerules. The spider web has great importance for spider life, including those which are not spinning the trap nets. The caught prey is frequently spun by a spider with web.

All the spiders are predators. They are eating Arthropoda, mainly insects. Digestive enzymes are injected into a prey body, digesting partially food.

The fear related to spiders frequently has no reason. There is small number of very poisonous spiders. Spiders are very useful, they eliminate mosquitoes, flies, aphids, bugs, etc.

Order Araneae

Family Araneidae. All the spiders of this large family spin "classic" net, the form of which is known by everybody. These spiders are referred by the orb-web spiders because of the form of their trap net. At the Urals these spiders are the biggest (a length can reach about 20 mm).

Family Clubionidae. These are small nocturnal hunters. The spider (the photo on the left side) was found on a glazed tile of my bathroom at night (its size is about 5-7 mm).

Family Linyphiidae. The spiders of this family spin their web between leaves of various plants, and hang under the net. The spider bites a prey entangled in a web from below.

Family Lycosidae. The family name, "wolf-spiders", is related to a mistaken opinion of people who thought that these spiders attacked in a group.

Family Philodromidae. At the Urals, these spiders can be seen on the leaves of woody plants. On the left photo, Philodromus sp. is sunning itself under spring sun.

Family Pholcidae. These are warm-requiring spiders. At the Urals, they can only live inside of houses, where they can be frequently found out.

Family Salticidae. The jumping spiders are very active during the sunny days. They are very attractive with large eyes.

Family Tetragnathidae. These spiders like damp places. They spin a web similar to the orb-web.

Family Thomisidae. As to the species numbers, this is the largest family. The spiders are on flowers waiting for a prey. There is well-marked sexual dimorphism.

If you would like to have detailed information on spiders, please, refer to specialized literature. We only want to attract attention to this group, and emphasize that the spiders are NOT DANGEROUS! On the contrary, they are very useful, eating small insects and mites! Certainly, if you would come across a tarantula or a black widow spider (At the Urals it is unlikely! These spiders can be found at the border with Kazakhstan in rural area!), you should be careful.

Order Opiliones

Specimens of Opiliones are very similar to spiders of Araneae, but they have segmented abdomen and long thin legs, which are easily torn off, and they have not venom glands. There are about 2400 species, the most well-known one is on the photos.

We know these specimens of arachnida from the childhood. Many of us conduct "experiments" to tear off a leg of this creature, watching movements.

The ability to spin a web was discovered by a human being at the ancient times. In Ancient Greece the spiders were a symbol of skill and art.

The spider may be a symbol of perseverance. When a spider chose a place for its trap net, it would restore its net as many times as you tore off the web.

The textile made out of spider web threads has unique features. Unfortunately, unlike silkworm, which for the first time Chinese used for a production of silk, the commercial production of the spider web threads is impossible. Therefore, the works on synthesizing the web proteins are carrying out.

See section Spiders nets.

Spider and Prey. Preys and food of spiders are various insects (flies, bugs, beetles, etc.), and even other spiders. Frequently a prey may be larger a spider as large as 4-5 times. Female is bigger than male, and can eat the latter. Some spiders spin web around prey.

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