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The microsporidia Plistophora schubergi is represented by several subspecies. Despite their complete morphological identity they are characterized by host specificity but infect the brown-tail moth Euproctis chrysorrhoea L., a probable initial host of the species. A single passage of the subspecies P. schubergi noctuidae, normally peculiar to owlet moths, through Euproctis chrysorrhoea does not change its specificity. P. schubergi schubergi and P. schubergi noctuidae differ also in their temperature optima. This suggests a divergence of biochemical and physiological characters of the subspecies. Further divergence of the subspecies resulting from their parasitism in different insects can cause a new speciation.

The paper presents a review of the literature dealing with studies of the cycle of development of Toxoplasma gondii Nicolle et Manceaux, 1909. Recently obtained data concerning the presence of sexual stages and oocystformation in the life cycle of the parasite are discussed. These are very essential for further investigations of epizootology and epidemiology of toxoplasmosis as well as for further elucidation of the taxonomic status of T. gondii and other similar Protozoa.

Studies of cattle, zebu and buffaloes for the presence of Coccidia carried out in Azerbaijan have shown considerable morphological differences between Eimeriasmithi and E. bovis and between E. zurnabadensis and E. canadensis, which are treated by some authors as synonyms. On the basis of peculiarities of the structure and literary data the authors accord E. smithi and E. zurnabadensis distinct specific status.

11 strains of leptomonad cultures obtained from various species of lizards and snakes in Turkmenia (1963 to 1967) were studied on white mice, golden hamsters and red-tailed gerbils. The maximum observation period was four months. The development of leishmaniosis was observed in no case. Microscopical and histological studies of the skin and parenchymatous organs done at various periods from the moment of infection have not established the adaptation of parasites of reptiles to mammals.

The curve of change of anchor's length and their point on ages of hosts coincides with that of growth of thickness of secondary gill filaments. This is a direct adaptation of parasites to dimensions of gills which secures their life by preserving young fishes. The size of copulatory complex changes with increasing host's age most only in species with large cirrus. Dispersion of monogeneans on skin of young fishes with great intensity and penetrating of larvae on those not via mouth but by the setting on skin — are also adaptations to preservations of young fishes and worms. The most constant characters of species are the shape and sice of point (blade) of hooks in Dactylogyrus and Tetraonchus and anchors in Diplozoon (the most "ancient" organs). Development's cycle of dactylogyrens can include one or many generations in dependance from age of hosts on which the larvae are setting. In the second case development goes as if with "intermediate" hosts.

Metacercariae of Eurytrema pancreaticum penetrate the pancreas by passing through the stomach into the duodenum and then into the main excretory pancreatic duct. Marita becomes mature in 45 days. The development of eggs in the uterus from the moment of fertilization till the formation of miracidium takes 30 to 35 days.

Among trematodes of the family Cyclocoelidae there were found twin-species which being almost absolutely identical morphologically differ in the presence or absence of pigmentary ocelli in embryos. However, the biology and phases of the life cycle of these suckers are entirely different.

In the intestine of Cheolodacthylus bergi Normann from the Pathagonian Shelf there was found a new species of the trematode, Pycnadena cheilodacthyli sp. n. (fam. Fellodistomatidae Nicoll, 1913). It differs from all known species by smaller sizes of the body, structure, shape and location of the genital apparatus.

It was found out by the histochemical method that in some nervous and muscular structures of Eustrongylides excisus Jägerskiöld (1909) takes place hydrolysis of acetyl-butyrylthiocholine. Colour of the tissue is most intensive with acetylthiocholine as compared to butyrylthiocholine. Eserine (10~5) decreases reaction to substrates. These data suggest that cholinesterase is present in the nervous and muscular tissues of E. excisus.

Hitherto only one species of the genus Angiocaulus Schulz, 1951, A. gubernaculurri (Dougherty, 1946), was known. The species occurs in North America and is known to be a parasite of martens. The new species differs from it in sizes of the body, length of spicules, structure of gubernaculum and in quite a different structure of the dorsal rib of the bursa. The paper gives an enlarged diagnosis of the genus with regard for peculiarities of the structure of the new species.

The review presents new data concerning the nature of interrlations between agents of transmissive rickettsioses of man and their biological vectors, bloodsucking arthropods. Ticks and insects are initial hosts of these microorganisms. Intensive multiplication of rickettsiae proceeds in vectors and some species can even accomplish a definite cycle of development in them. Arthropods and rickettsiae are characterized by a parasitic type of relationships. The agent's pathogenicity can vary from 100 per cent lethality (e. g. lice infected with Rickettsia prowazekii) to life preservation (e. g. ixodid ticks and trombiculid mites). A close interadaptation of ticks and rickettsiae is manifested also in the ability of the agent to transovarial transmission throughout many generations. The specificity of interrelations between arthropods and rickettsiae is reflected in the connection of subgeneric groups of these microorganisms with definite groups vectors or, at the specific level, in quantitative differences in the threshold of infection, speed and frequency of generalization of infection, frequency of transovarial transmission and other peculiarities common to definite species of agents and vectors.

It was established the repellent activity of carboxyde, cusol A, DETA (prepared from oil metaxylene), dibutylamid of valerianic acid, (RC—28), RP-1, butylacetanilide, isoamylacetanilide, dibutyl ester of succinic acid, R-228, R-203 and other preparations and their mixtures in different combinations in relation to ticks Rhipicephalus turanicus B. Pom., Hyalomma detritum P. Sch., H. asiaticum P. Sch. et E. Schl., and H. dromedarii Koch.

Investigations carried out from 1968 yo 1970 have shown that in winter period in many basements proceeds an intensive hatching of Culex pipiens molestus. The water acidity in basements where larvae of mosquitoes were found was from 7.5 to 8.5°, oxidability — from 25 to 100 mg/l O₂. The temperature of water in one third of all examined basements varied from 5 to 10°. Under experimental conditions females of C. p. molestus can stand freezing to—10, —12° during two hours and after warming lay eggs normally. Eggs remain viability on wet substratum to 11 days and can stand freezing at the temperature of —12° during three hours. The resistance to freezing increases from generation to generation. Larvae and pupae withstand short-term freezing and after warming develop normally.

Experimental studies were carried out of the metamorphosis of Ctenophthalmus dolichus Ioff, 1953 that parasitize the great gerbil during the cold season of the year. It was established that the whole life cycle of these insects occurs at a temperature of 8 to 26° and relative humidity of 89 to 100%. Temperature of 25 to 26° and humidity of 95 to 100% were found to be the optimal conditions for the development of fleas (hatching of adults in 19.2 to 36.7% of eggs). A small number of individuals completing the whole metamorphosis indicates that fleas of Ch. dolichus are insects of low viability. The development rate of preimaginal phases depends on the temperature. The developmental period of fleas decreases from 338 to 22 days with temperature increasing from 8 to 26°.

Analysis of the structure of the aedeagal hook, horizontal branch of the 9^ht male sternite and their articulation confirms the validity of separation from the family Ceratophyllidae sensu Ioff et Scalon, 1954 and belonging to the family Leptopsyllidae Roths, 1915 sensu Hopkins et Traub, 1955 of the following genera: Leptopsylla (with subgenera Leptopsylla and Pectinoctenus), Sigmactenus, Peromyscopsylla, Paractenopsyllus, Cratynius, Amphipsylla, Paradoxopsyllus, Brachyctenonotus, Frontopsylla, Ophthalmopsylla, Geusibia, Phaenopsylla, Hopkinsipsylla, Ctenophyllus, Odontopsyllus, Mesopsylla, Acropsylla, Caenopsylla, Ornithophaga, Dolichopsyllus.

The ability of fleas Ctenophthalmus congeneroides Wagn. to perceive and transmit tick-borne encephalitis virus during feeding on adult white mice has been studied experimentally. During feeding of hungry females of C. congeneroides on white mice infected with tick-borne encephalitis virus the former were infected with this virus. In 24 hours during new bloodsucking these fleas transmitted the virus to healthy white mice. On these white mice a new series of fleas, was infected with the virus.

The paper contains data of seasonal investigation of ectoparasites of the common red-backed vole (Clethrionomys glareolus Schr.) and inhabitants of its nests in middle taiga of the Komi ASSR. The material obtained enabled the author to study interrelations between the host, ectoparasites and inhabitants of its nests based on close topic and trophic links. According to topic relations all collected arthropods were arranged into three biological groups (host, host-nest and nest inhabitants). According to their type of feeding all inhabitants are grouped in the following way: parasites predators, saprophages and phytophages.

Materials are given on the biology and ectoparasites of Myotis mistacinus Kohl. and M. oxygnathus Mont. from the delta of the Cherny Irtysh and foothills of Monrak (the southeastern part of Zaisan hollow).