Spider SVG – a group of arthropods, the first in the number of known species in the class of spider-like (previously considered the second after ticks, when all the ticks were united in one group). Representatives of the group are widespread. Spiders SVG are obligate predators, feeding primarily on insects or other small animals. Only one exception is known – Bagheera kiplingi, a horse-spider that feeds on green parts of acacias. The group includes about 42 thousand modern and about 1.1 thousand fossil species.
Spider SVG Description
The body consists of two parts: the head chest and mainly the undivided abdomen, connected to each other by a thin stem (Latin petiolus s. Pediculus), usually short, less often considerably elongated (in genera Myrmecium, Formicinoides); the head of the thorax is divided into two distinct areas: head and thoracic; the first one carries two pairs of extremities: Chelicerota, chelae, mandibulae, consisting of one thick, usually short segmented segment armed with a mobile claw, near the tip of which there is a hole in the canal that excrete poisonous secretions of glands in the main segment, and palpi, consisting of 6 segments (coxa, trochanter, femur, patella, tibia and tarsus). In mature males, the tarsus pedipalp was converted into a cohabiting apparatus – cimbium.
Between the chelitzers at the top of the bump (rostrum) there is a mouth opening for sucking; this bump is bounded from below by the front process of the chest (sternum), the so-called lip (pars labialis), and on the sides by two maxillary plates (lamina maxillares).
Behind the pedipalp there are four pairs of legs attached to the head chest, each of which consists of 7 segments: basin (plough), a trochanter, femur, cup (patella), tibia, metatarsus and tarsus, armed with smooth or serrated claws from below, between which there is sometimes a shorter unpaired claw.
On the front convex frontal part of the head chest, which in some genera takes the form of a cone (Theridion, Erigone), and on top of which there are chelitzers (Eriauchenius), and on top of which there are pointed eyes, there are 8, 6 rarely 2 (genera Nops and Caponina), usually located in two straight or curved rows, sometimes as in Pholcus podophthalmus E. Sim., lateral eyes are close by three and located on corneal processes. Eyes are simple, of two genera: the middle pair of front eyes, so-called frontal or main, is provided with special device of retinoids and accommodation apparatus, the other eyes are called usually additional (middle back also – parietal) and have internal reflecting layer (tapetum lucidum).
The abdomen is mainly oval, less often round, angular, or equipped with various kinds of processes (genus Gasteracantha, Phoroncidia), and sometimes has a very elongated, worm-shaped shape (Ariamnes flagellum Dol.); from the bottom near its base there is a sexual aperture, in males it is in the form of a simple transverse slit, and in females it is surrounded by a thickened chitin plate – epigynum s. sarum with a tongue-shaped, curved process (clavus s. ovipositor).