From Big Medical Encyclopedia

ARTHROPOD (Arthropoda) — the type of backboneless animals which is characterized by geteronomny segmentation of a body and existence of an outside skeleton. Phylogenetic it is connected with annlides. Combines apprx. 1,5 million water, land and parasitic activities. Are widespread in all geographical zones h.

Distinguish 4 subtypes from Ch.: the subtype of trilobitoobrazny (Trilobito-morpha) includes the died-out class of trilobit (Trilobita); a subtype of zhabrodyshashchy (Branchiata) — a class of Crustacea (Crustacea); a subtype of he-litserovy (CheJjcerata) — classes of merostomovy (Merostomata) and arachnoid (Arachnida); the subtype tra-heynodyshashchit (Tracheata) — classes of myriapods (Myriapoda) and insects (Jnsecta. or Hexapoda).

Value Ch. for the person is diverse. Many ectoparasites of the person (see Parasites) from a class arachnoid (see) are carriers of causative agents of transmissible diseases, (see), and also causative agents of nek-ry infectious diseases, napr, itch mites — causative agents of itch (see). The class of arachnoid includes also poisonous spiders of many types (see. Poisonous animals). Big danger to the person is constituted by stings of a spider of a karakurt, the South American spider «a black vdovushka», a spider racer. Among mites (see) there are wreckers of grain — granary mites, wreckers of plants — web mites. Among a numerous class of insects insects — carriers of causative agents of transmissible diseases have the greatest medical value, nek-ry of them are causative agents of diseases, napr, mia-call (see), and also ectoparasites of the person and animals (see Fleas, Whigs, Mosquitoes blood-sicking, Mosquitoes). Mass attack of blood-sicking insects (see Midges, Mosquitoes blood-sicking, Wood lice, Mosquitoes, Midges, Gadflies) on people. working in a taiga and the tundra, deprives of them normal rest, reduces labor productivity, increases traumatism; causes huge losses to livestock production. The considerable number of species of insects is the phytowreckers causing a big loss to agriculture (see Wreckers of crops), wreckers of grain (see Wreckers of grain, grain products). Useful types — pollinators of plants occur among insects. Widely the person of a silkworm, a honey bee uses (see the Bee, Apitoxin), scale insects, insects, to-rye produce paint and other valuable products. Trade types, napr, shrimps, crabs, lobsters, spiny lobsters belong to the class of Crustacea.

Ch.'s body is covered with the dense cuticle consisting of complex polysaccharide of chitin and proteins; at some Ch. the cuticle is impregnated with carbonic salts that turns it into an armor. Mobility of somites is reached thanks to existence between firm sites of a cover of sites with the thin, collected in folds cuticle. The body consists of the head and a trunk, to-rye are divided into uniform segments (at myriapods) or into the segmented breast and an abdomen (at insects). At the majority of Crustacea, and also at arachnoid the head and a breast are merged, forming a cephalothorax, at mites — a body conjoint. Bodies of the movement — jointed extremities. Existence

of 3 pairs of legs (the highest insects have 2 pairs more of wings), for arachnoid — 4 couples is characteristic of insects, at nek-ry myriapods the number of extremities can exceed one hundred. The nervous system consists of a nadglotochny ganglion, or a brain, peripharyngeal konnek-tiv and a belly nervous chain. Ch.'s brain is differentiated that is connected with complexity of behavior and existence of advanced sense bodys — compound eyes, acoustic organs, bodies of perception of smells, organs of touch. The circulatory system which is not closed is filled with a hemolymph. The respiratory system at the majority land Ch. is presented by tracheas or lungs (at arachnoid), at living in water — gills; at many ticks who are living in conditions of high humidity and having a thin cuticle, gas exchange is made through skin. The oral bodies — gnawing, sucking or kolyushche-sucking (at the majority of parasites). The digestive channel is divided into a front, average and back gut. Eliminative organs are malpigiyeva vessels, the antenna of l ny and the cook - sebaceous glands. Motive muscles cross-striped, very strong. H razdelnopola are more often, hermaphrodites meet. Syngenesis, sometimes parthenogenetic. Ch.'s most belongs to oviparous forms; postembryonal development direct or with transformation. Growth happens in the period of a molt. The way of life is heterogeneous. The most primitive Ch. live in water, others passed to land life, at many a life cycle passes Ch. partially in water, partially on the land. High-organized Ch. (bees, ants, etc.) differ in difficult behavior and form the whole communities with division of labor between individuals.

See also Insects, Arachnoid - Crustacea.

Bibliography: Gilyarov of M. S. Zakono

of regularity of devices of arthropods to life on the land, M., 1970; Life of animals, under the editorship of JI. A. Zenkevich, t. 2 — 3, M., 1968 — 1969; Ivanov A. V. Spiders, their structure, a way of life and value for the person, JI., 1965: Determinant of the ticks living in the soil, under red, M. S. Gilyarova, p.1 — 3, D., 197-5—1978; To Oprah

a divider of the arthropods damaging health of the person under the editorship of V. N. Bsklemi-

of a shev, M., 1958; The Textbook of medical

entomology, under the editorship of V. N. Beklemishev, p.1 — 2, M., 1949; Shvanvichb. N. Kurs of the general entomology, Introduction to studying of a structure and functions of a body of insects, M. — L., 1949. A. A. Zemskaya.