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On the basis of literary data and original investigations some phylogenetic, ecological and morphological aspects of the origin of parasitism in trombiculid mites are carefully considered for the first time. It is shown that parasitism in this group of trombidiform mites is a relatively young historical phenomenon and was formed after their ontogenesis had differentiated into active and quiescent stages. Therefore, in the life pattern of trombiculid mites the character of individual development, that defines their biotopical restriction, is much more important than the phase parasitism. Primitive organization of the digestive system and extraintestinal digestion, so characteristic of this group, are one of the main reasons of the origin of their parasitism. Under pasture conditions trombiculid mites, that initially were predators-entomophags with bite-sucking mouth parts, pass easily to parasitism on vertebrate animals and become primary lymphophags. They use the vertebrate host's organism exclusively as a source of food and by the extent of polyphagy are very close to free-living blood-sucking insects. Stylostome, that develops during feeding of trombiculid larvae and some other closely related groups of trombidiform mites, is a universal structure for achieving a large amount of food on a wide range of animals during a relatively short period of time and reflects wide host-parasite specificity of these parasitic mites. From the historical view the larvae of trombiculid mites did not pass from one group of hosts to the others, but owing to morphological preadaptation to parasitism passed in a befinite historical period, not earlier than Paleogene, to parasitism on all classes of terrestrial vertebrates, especially on mammals, their primary hosts.

Microbiocoenoses being formed in burrows of little souslik have been investigated. Microbiocoenoses of sloping burrows have most simple organization. Comparative analysis of the fauna and functional structure, conducted during the spring-summer period, has not shown the existence of any directed process in the development of microbiocoenoses of sloping burrows. On the contrary, microbiocoenoses of vertical nest burrows can be regarded as biocoenotic systems dynamic in space and time. Here in the period of robent's vital activity occurs a constant construction of underground passages and periodical change of nests. In this case the fauna of new nests is formed largely at the expense of migration of nidicols along free or obstructed with loose earth underground horizontal passages. Microbiocoenoses in burrows of different types are not connected between each other by morphoprocess and their development is of independent character.

Experiments with nymphs of Ixodes persulcatus and Dermacentor marginatus have shown that the rate and degree of engorgement, dropping off from the mouse, metamorphosis longevity and weight of emerging imagos change under plant odour influence. The influence of acetone extract vapours of pepper, poplar buds, linden and aspen was tested. Under the influence of the vapour, acting as an attractant for the adults, engorgement weight of their nymphs and the weight of imagos emerging from them increased; attractants change the nymph-imago metamorphosis duration as well. Repellentacting odours, as a rule, produce an opposite reaction. The phenomenon of the inversion of the infected D. marginatus reaction to the odour is proved in nymphs. Attractant for naive adult ticks (poplar buds) increased the time of feeding and weight of nymphs in comparison with the control. Just the opposite: nymphs infected with tick-borne encephalitis (TBE) virus produce an opposite reaction — weight decrease under influence of poplar buds as the repellent. Importance of the above phenomena for the ticks distribution and TBE epizootology is discussed.

Variability of 10 morphometric characters at all phases was investigated on laboratory cultures of R. turanicus and R. bursa. It has been shown that variability increases from phase to phase. R. turanicus nymphs of both sexes differ in the length of gnathosoma and length of the 1st tarsus. In nymphs of R. bursa sexual dimorphism manifests itself on 8 characters, in all cases sizes of organs are greater in female nymphs. Besides, engorged female nymphs are reliably greater than male ones in length and mass of the body. Mature females and males of R. bursa also reliably differ in the total body length as well as in sizes of all examined structures. Females and males of R. turanicus do not differ in body length but differ in 9 other morphometric characters. Correlation analysis of characters was carried out individually for each phase and sex. Correlation coefficient between characters are most low in larvae. In R. turanicus male and female nymphs the coefficients are close. In R. bursa female nymphs correlation coefficients are noticeably lower than in male ones. The level of independence of characters in female nymphs defines the degree of manifestation of sexual dimorphism at this phase: the closer the links between characters, the lesser the number of characters revealing sexual differences. Coefficients of correlation of characters coincide in males of both species. In females of R. turanicus they are lower than in males that determines the strengthening of sexual dimorphism at the phase of imago. In R. bursa distinct sexual dimorphism is attained as early as at the nymphal phase and a further weakening of links between characters is not necessary. Correlation coefficients of characters in R. bursa females do not differ from those of males.

The authors' own and literary data on blood parasites of the genus Haemoproteus found in Coracias garrulus have been analyzed. Morphometric characteristics, figures and micrographs of macro- and microgametocytes are given. The parasites found are described as a new species, Haemoproteus hachmasensis.

The results of studies on the frequency of distribution of the infusoria Ichthyophthirius multifiliis in a bleak population are discussed. In wild populations the relationships within the host-parasite system have been found to be regulated, in general, at the organism's level. Therefore, there is a poor correlation between the theoretical and empiric values of distribution frequencies broadly used in parasitology.

Of 8 species of bullheads and oil-fishes from Lake Baikal plerocercoids of diphyllobothriids were found in the coastal-pelagic species Cottocomephorus grewinkii and C. inermis and in one benthopelagic-deepdwelling species Limnocottus megalops. Over 90% of plerocercoids are identified as Diphyllobothrium dendriticum (Nitzsch, 1824) but their growth is retarded. Analysis has been conducted of the infection of C. inermis and C. grewinkii on the water area and at depths of the lake depending on the size and age of the fishes and season. The question whether C. inermis and C. grewinkii are additional or reservoir hosts of D. dendriticum in the Baikal ecosystem requires additional experimental studies.

Cultivation of Trichinella muscular larvae, purified by centrifugation in 20 ... 50 % saccharose density gradient, in protein — free nutrient media at a dosage of 3.5—4*103 lar./ml in the presence of insulin has made it possible to obtain a soluble antigen of Trichinella. It has been shown by means of electrophoresis in polyacrilamid gel that the soluble (secretory-excretory) antigen has three protein fractions while the somatic trichinnellous antigen has 18 fractions. It has been shown that the soluble (secretory-excretory) antigen can be used for immobilization of erythrocytes on the surface that enables the sensitivity and specificity of serological methods for diagnosis of trichinellosis to be increased.

Trematode invasion and different concentrations of lead nitrate 0.01, 0.1, 1 mg/l-1 impact on breath peculiarities of coil-flats have been investigated. Affected by invasion the length of air inhales is more durable and interim intervals shorter, single volume of inhaled air by lungs at every other inhale is 1.3 times larger than in invasion free animals. Non-intoxicated with 0.1 and intoxicated with 0.01 mg/l-1 species get acute poisoning, a depression stage. The length of intervals between every other air inhale increases 1.5 to 2 times and single inhale volume reduces on the average by 26.5%. With 1 mg/l-1 of toxicant sublethal and lethal stages of poisoning soon subsequently follow during which one can watch a progressive depression of breathing function up to its complete extinction. Clinic toxication picture in toxicated species is more patent and pathological process is completed with lethal end much earlier than in case of invasion free animals.

A new species of blackflies, Nevermannia kugitangi Yankovsky et Shinkovsky sp. n., is described. Larvae and pupae of the species were collected in small sulfur sources flowing on spurs of the Kugitangtau Mountain Range (the boundary between Southern Uzbekistan and Southern Turkmenia). The new species differs from the related species Nevermannia vitilis (Rubzov, 1955) by wider ventral plate (the length of the body is no more than 0.5 of the width while in N. vitilis this ratio is no less than 0.75), by short medial rib of ventral plate (in N. vitilis it significantly extends beyond the posterior edge of the plate), by more narrow median sclerite (its length is 20 times more than width, in N. vitilis this ratio is no more than 8:1) in males; by absence of conical posteromedial projections on the arms of genital fork, by narrow sickle-formed anal sclerites in females; by smaller postgenal cleft and by 4 lateral setae per side of hypostoma (not 2—3 as in N. vitilis) in larvae; by presence of median projection and absence of large lateral openings of cocoon in pupae. Type-material of the species is preserved in the collection of Zoological Institute, Academy of Sciences, St. Petersburg.

Multisetosa acerbus sp. n. is described from mountains of Southern Daghestan, the Caucasus. The new species is similar to M. persicus Vercammen-Grandjean, Rohde et Mesghali, 1970, but differs in a greater value of most measurments, including Index Pedis, greater number of dorsal, ventral and postposterolateral setae and absence of short basalcilia on sensillae. All type specimens are preserved in the Zoological Institute, Academy of Sciences, St. Petersburg.

Haller's organ of Anomalohimalaya lotozkyi female has a capsular opening in the shape of a cleft with lobed margins (Fig. 1, 1; 2, 1, 2), in larva this organ has also a cleft-like irregular opening with a great number of lobes (Fig. 1, 2; 2, 3, 4). The number of sensory elements corresponds to that of other genera of the subfamily Amblyomminae, excluding Haemaphysalis and Hyalomma. Specific characters of sensillae are as follows: large size of the porous hair of the anterior group and remoteness of postcapsular group from the cleft.

A new species, Blastocystis anseri, was found in domestic goose. Sizes of blastocyst in culture are 7.5—46.2X7.5—46.2 m. Method of cultivation of Blastocystis anseri on biphase egg medium was worked out. Liquid phase can be made of Henks solution or 199 medium with an addition of 30—40% hen or bovine serun. Optimum temperature for cultivation is 39±0.5°, ph 7.0—7.2.

In the subtegument of scolex and neck of mature cestodes Sobolevicanthus spasskii and Diorchis stefanskii there were found processes of nerve cells, which by the composition and situation of organelles in them can be regarded as forming receptors. The role of different organelles and inclusions in the morphogenesis of the latter is discussed. Since some sensitive endings in the scolex and neck are not formed yet a conclusion is drawn on the necessity of a more careful approach to the separation of new receptors and on the necessity of a critical view on the known ones. It was found out that nerve processes, containing structural elements of a sensitive ending, get into close contact with the processes of the cytons of the tegument. In this connection an idea is suggested on the correlated development of the nervous-tegumental zone during the formation of the receptors.

A new species of blackflies, Montisimulium danijari sp. n., from northern Tien-Shan is described. Morphological characteristics of all developmental phases are given; photomap of polytene chromosomes is drawn up.

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