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Analysis of food, positional and temporary relations between insects, ticks and terrestrial vertebrates suggests the following types of parasitism in these animals: 1 — free-living bloodsuckers; 2 — nest-burrow bloodsuckers; 3 — temporary ectoparasites with a transigtory feeding; 4 — temporary ectoparasites with a long feeding; 5 — constant ectoparasites; 6 — intracutaneous endoparasites; 7 — cavitary endoparasites; 8 — tissue endoparasites. Different forms of parasite—host relationships between arthropods and vertebrates are recurrent and independent but direct paleontological data on the origin and evolution of the most important taxons of parasitic insects and ticks are very scarce or laking.

It has been shown that during feeding the midgut epithelium of the human louse Pediculus humanus corporis consists of three types of cells: secretory, digestive, and reserve (regenerative) ones. According to the ultrastructural organization the secretory cells are subdivided into two regions — apical and basal. In the apical region of the secretory cells no microvilli are observed. The basal region contains mitochondria, ribosomes, rough endoplasmatic reticulum, microvesicular bodies and secretory granules. Three types of secretion of digestive enzymes (macroapocrine, microapocrine and merocrine ones) were found. The apical surface of the digestive cells is covered with microvilli; the cytoplasm of the digestive cells is filled with lipids and glycogen granules. Cells are lined with a homogenous basal membrane.

The occurence of an isolated population of I. persulcatus in the health resort zone of Leningrad is due to a character of vegetation, soils, relief and availability of such food sources as birds, hares and elks. The seasonal dynamics of ticks abundance depends very little on temperature but denepnds on the amount of precipitations and on the number of days ,with precipitations; long fluctuations in the ticks abundance are stimulated, in general, by temperature. Annual mechanical collections of ticks in nature and their chemical extermination on a small area do not affect sufficiently the abundance of populations.

Observations have shown that the fungus Coelomomyces iliensis can be spread with the water current by means of shallow water species Aplocheilus latipes, Pseudorasbora parva, larvae of beetles of the family Dytiscidae, flies Musca domestica and ants. The parasite has been found to be pathogenic not only for larvae but also for pupae and imago of mosquitoes of the genus Culex. The agent was first found in larvae of Anopheles maculipennis in the basin of the Cherny Irtysh river. This extends the range of hosts of the fungus and its distribution area.

The authors give the analisis of the best known systems of nematodes, parasitizing vertebrates. The classifications of Ghitwood (1933, 1937); Skrjabin et Schultz (1940) and Chabaud (1974) are discussed. A new variant of the system of the mentioned nematode groups is proposed, the classification of Chabaud being assumed as its basis. In the subclass Adenophorea the authors distinguish two orders — Trichocephalida and Dioctophymida. The subclass Secernentea includes according to Chabauds system five orders: Rhabditida, Strongylida, Oxyurida, Ascaridida and Spirurida. Two suborders — Ascaridina and Heterakina are distinguisched in the order Ascaridida, three suborders — Spirurina, Cammallanina and Filariina — in the order Spirurida. The suborders Gnathostomatina and Gucullanina are admitted to be not enough valid. Both these groups are considered as superfamilies in the new variant of classification. A conception of the close phylogenetic relationships between the orders of the subclass Secernentea is championed. The authors believe that the historical development of the representatives of this nematode group occured from the rabditiform worms towards the strictly specialized parasitic forms, which are met in the order Spirurida. The representatives of the order Rhabditida are the most closely related to the ancestral forms of the subclass Secernentea.

There are glandular elements of syntitial structure in parenchyma of scolex base of T. crassiceps larvae. They are located behind the suckers at the invaginated state of scolex. Perikaryons of gland contain dense rodshaped, spheric granules and great accumulations of electron-dence substance in vacuoles. The same types of secretary product are found in the rostellar tegument. The glandular elements are mostly developed in the period of the formation of rostellar hooks, but they are well expressed too in mature larvae thus providing morphofunctiorial specialization of rostellar tegument.

Lipids of the cestodes R. tetragona and R. echinobothrida, parasites of chickens, were studied by thin-layer and gas-liquid chromatography methods. The quantity of neutral lipids amounts to 74.4% in R. tetragona and to 73.1% in R. echinobothrida. Triglycerides amount to 35.6% and 38.4% of the neutral lipids in these species, sterols to 21.6% and 17.2%, sterol esters to 25.1% and 32.0%, diglycerides to 2.8% and 1.4% and free fatty acids to 7.8% and 6.5%, respectively. Fatty acids content of worms is similar but not identical ot that of chicken intestine lipids. Cestode infection affects the lipid content of chicken intestine resulting tn the decrease of triglycerides and oleic acid quantities and in the increase of the amount of free fatty acids and stearic acid.

Morphogenesis of the genital system of 14 species of nematodes of the superfamily Tylenchoidea was studied. The evolution of the genital system of females in the superfamily was considered. The initial type for the group is a paired gonade of the females. In different families the reduction of the hind branch of the gonade proceeds in parallel. During ontogenesis the development of the posterior part of the trophicogenital department and the gonade branch restrains. In the family Pratylenchidae this phenomenon is associated with the shortening of the body during the transition to endoparasitism; in the family Tylenchidae the phenomenon is connected with the acquiring of the streamline form suitable for living in humid biotopes. In the family Anguinidae takes place the hypertrophy of the female genital system connected with the transition to the cavitary endoparasitism. A new technique for making preparations of nematodes is suggested.

Parasitological studies of fishes from fresh waters of the Kaliningrad region have revealed 17 species of sessile peritrichids of which three species are new. A description of the new species is given.

Descriptions and size indices of Hirundinellidae species (Hirundinella ventricosa (Pallas, 1774) Baird, 1853 and Uroproctinella cochinensis Sahai et Srivastava, 1978) were compared. As a result the latter was established to be a synonym of H. ventricosa. Described under the same name both species of the genus Opisthomonorcheides (Monorchiidae) are undoubtedly valid. The name of the senior homonym, O. indicus Karyakarte et Yadav, 1976, is retained and a new name, O. jamilahmadi nom. nov., is suggested for the junior homonym.

A diagnosis of the new genus Crossonemoides is given. The genus is close to the genus Neolobocriconema but differs from it by the external cuticular membrane in adults and fringed processes on the cuticle of larvae which do not form longitudinal rows. Nothocriconemoides justus sp. n. differs from the close species N. lineolatus by having a greater number of cuticular rings on the body, their smooth edge without longitudinal striation and by the number and shape of rings on the cephalic end of the body. As compared to the close species C. amorphus Criconemoides sabulosus sp. n. has a different structure of the labial region and undulate edges of cuticular rings.

Summary is absent.