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Summary is absent.

To carry out mass sanitation measures it is necessary to study thoroughly the parasitological situation over a given territory: quantitative and qualitative composition of the fauna of parasites, their vectors, intermediate and reservoir hosts, their spread in biocoenoses, biocoenotic links, their dynamics in space and time, concrete peculiarities of the environment (both natural and social) effecting in this or that way the number, distribution and development of pathogenic agents, the mechanism of their transmission from infested hosts. A comprehensive ecological-parasitological study of biocoenoses, the investigation of the circulation ways of parasites in nature and mechanisms of their transmission to animals and man is the most important. On looking into a parasitological situation, apart from biological means of investigation, physical and mathematical methods must be used to study the state and dynamics of the number of populations of parasites and bloodsucking arthropods and their dependence on the environmental factors.

The activity of fasting adults Dermacentor marginatus Sulz. and its dependence on the photoperiods and temperature was investigated experimentally. The investigation comprised an observation on tick behaviour in a special device and a registration of their distribution between plants (dry grass stalks) and litter (paper strips). Ticks at the top of stalks (in "waiting pose") were considered for "active", those at the bottom or in the litter — for "passive". The distribution of ticks — young and mature adults — within 2—3 months has shown that their activity was controlled by the photoperiodic reaction of short-day type. Moderate temperature and short day promote the active state of ticks, on the contrary, high temperature and long day cause the rapid inactivation and their fall into the passive state. Photoperiodic dependence of the imaginal activity supports a consideration of the summer quiescence of fasting females of Dermacentor marginatus as an example of behavioural diapause which is independent of morphogenetic diapause.

The effect of photoperiodic regime upon the larval development and the appearance of diapausing eggs in Aedes triseriatus Say has been studied. The larval development is checked by the day length: while 20 light hours per day favour the pupation of all larvae, 10 light hours result in a long delay of development at IV^th stage and the subsequent mortality of larvae, connected with the temperature unfavourable for normal hibernation. Photoperiodic effect becomes appearent at the low temperature (15° C) and weakens at the high temperature. The appearance of diapausing eggs is also connected with photoperiodism. If females and eggs laid by them are under the effect of 10 light hours, the hatching not observed; under the effect of long day 60% of larvae hatched. The cooling of diapausing eggs and the subsequent long day effect stimulate the hatching of larvae, however the number of such larvae does not show the direct proportional dependence on the cooling duration. The change of short-day illumination for long-day one at T 20—23° С terminates the diapause causing the hatching of the first larvae after 15 days. Photoperiodic conditions within the life of female do not influence upon the induction of egg diapause.

Echidnophaga oshanini Wagn., distributed in North-Western Mongolia and in the Tuva ASSR, parasitizes the mongolian pika (Ochotona pricei Thomas). The spread of these fleas within their range is limited by the vertical zone 1400—1500 m above the sea level and is associated with semi-deserts and mountain steppes. The number of adults is largest in June—July, whereas in cold season the fleas nearly utterly disappear. The fleas hibernate in the cocoons. By the nature of interrelations with the host the females of E. oshanini are to be referred to the category of stationary parasites. Upon finding a suitable place on a warm-blooded animal the fleas attach themselves to the host by piercing their long proboscis' into the animal's skin. The fleas do not leave the host, even do not change the place of attachement. Just after attaching the fleas start feeding. Since this time blood goes into their intestine without pause, only its insignificant portion being accumulated. The greater portion of the blood is excreted from the organism being little affected by digestion. On the first day of fleas' stay on the host the copulation takes place. By the end of the second day the female lay eggs. In the cause of feeding the number of eggs increases. Mature females are capable of laying more than 19 eggs a day. The eggs are smooth and easily roll down without sticking to the rodent's hair. The fleas are capable to delay the oviposition of mature eggs under the influence of daylight. As a result of this adaptation the oviposition may take place only when the host is in the nest. Taking into consideration the maximal time of fleas stay on the warm-blooded animal and the dynamics of oviposition each female is supposed to be able to lay up to 500 eggs within its life span.

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15 species of fleas (tab. 2) were found on 7 species of small mammals examined (tab. 1) and in their nests. The data are given on the distribution of fleas on the hosts, on the seasonal changes of their number on animals and in their nests.

Observations have been made in the territory of the Pechora-Ilytch state reserve in the summer of 1964. The following 13 species of the genus Culicoides have been recorded: C. chiopterus Mg., C. obsoletus Mg., C. pulicaris L., C. impunctatus Goet, C. fagineus Edw., C. grisescens Edw., C. stigma Mg., C. fascipennis Staeg., C. subfascippennis Kieff., C. pallidicornis Kieff., C. cubitalis Edw., C. carjalaensis Gluch., C. truncorum Edw. Breeding sites of 9 species have been found out. The flight and biting activity of midges were observed from the beginning of June in the beginning of October. Two peaks of the midges number have been recorded at the end of June and in the middle and end of August. C. chiopterus, C. obsoletus, C. pulicaris and C. grisescens are the most common species. All these species excluding C. grisescens have two generations. C. carjalaensis and C. truncorum have not been reported as attacking men and animals.

Triaenophorus nodulosus and Tr. crassus are widely distributed parasites of fishes in the greater part of Holarctic. The borders of the distribution of the both species depends first of all on the availability of their definitive host, pike. The southern border of the spread of these parasites in the USSR sometimes does not reach the border of their host area (the Kura basin, the Upper and Middle Amu-Darya and Syr-Darya). 59 species of fishes belonging to 7 orders and 11 families are recorded as the second intermediate hosts of Tr. nodulosus and 24 species — as hosts of Tr. crassus. In the European-Siberian part of the USSR Tr. nodulosus was recorded as a parasite of numerous fishes, but cyprinids, whereas in the Amur basin Tr. nodulosus was registered only in cyprinids. In northern water bodies of Europe and Siberia salmonids were found to be the second intermediate host of Tr. crassus, in southern water bodies of the European part of the USSR — Gobiidae and pike, and in the Amur basin — Eleotridae and pike. Apart from the differences in the life cycle there are observed significant morphological distinctions between Tr. nodulosus from the Amur basin, Tr. crassus from the Amur and southern water bodies of the USSR and northern forms of these parasites. So morphological difference and adaptation to certain hosts, proved experimentally, serve as evidence of species independence of Tr. nodulosus and Tr. crassus from the Amur basin.

Through investigations have shown that the taxonomy of Dactylogyridae, particularly Gyrodactylidae and Dyplozooninae, is elaborated rather insufficiently. Additional characters such as certain details of the shape and structure of chitinoid elements, which formerly were attached no importance, have been revealed. Basing upon these characters there were distinguished some new species by subdividing Dactylogyrus nanus, D. cornu, D. similis, D. chondrostomi, Gyrodactylus medius, G. nemachili, Diplozoon paradaxum etc. into several ones. A greater consideration should be given to the details of the shape of marginal hooks [according to Ergens (1965) they are also very stable in the limits of species in Gyrodactylus], to their points and the basal portion of the hook itself, to the shape of anterior-lateral angles of the dorsal bar of Gyrodactylus, to the ratio between the sizes and to the structure of the clamp, cuticle, gut and the posterior end of the body in Diplozoon. The shape of the bent (angles) of the anchors, their massivness, correlation of parts must be taken into consideration as well. A good quality of slides, accuracy and a large scale of figures or microphotos are also necessary conditions. In Dactylogyrinae all anchors may be arranged into 4 main groups, marginal hooks — into 5 groups, dorsal bar — into 4 groups, ventral bar — into 7 groups, copulatory organs — into 10 groups, vaginal armature into 4 groups. Correspondingly all chitinoid structures in Gyrodactylidae are grouped into several morphological types (marginal hooks, anchors and bars). The Kulwiec's (Kulwiec, 1927) numeration of marginal hooks is accepted by us. The "8th pair of marginal hooks" found in Dactylogyrus by Mizelle and Price (1963) is an additional tendon of the 6th pair of hooks mentioned by us in our earlier publications (Gussev, 1955, 1962).

The paper is the first attempt to study the circulation processes of helminths in biocoenosis over the investigated territory. The data are adduced dealing with the fauna of helminths of some predatory mammals, Muridae, reptiles, amphibians collected within 1964—1966. In all, 101 predators, 451 rodents, 218 amphibians and 18 reptiles were examined. A scheme of parasitic and food links of predators and rodents with various animals on the shore is given.

Summary is absent.

The present paper deals with the anatomy and systematic position of Mosesia pavlovskii sp. nov. found in the intestines of the following birds: Phylloscopus trochilus, Sylvia atricapilla, Hippolais icterina, Dendrocopos major, Larus ridibundus. The paper contains a detailed description of the species M. pavlovskii (fig. 1—3), its differential diagnosis and a key to the species of the genus Mosesia.

Ferment of acetylcholine esterase, hydrolysing mediator of nerve excitation of acetylcholines, is topographically connected with the nervous system. This has enabled the author to study the structure of the nervous system in some parasitic platyhelminthes by means of the method of hystochemical revealing of choline esterases. The paper contains a description of this method and certain details of the structure of the nervous system in two species of cestodes and trematodes.

Balanus balanoides, В. balanus and В. crenatus from the intertidial and sublitoral areas of Barents Sea, Murman, were examined for commensal Protozoa; 7 species of ciliates belonging to 6 genera of 4 orders are described. Hypostomatida are represented by the family Hartmannulidae (Trochilioides bathybius sp. n., Т. littoralis sp. n., Sigmocineta nordica gen. et sp. n.) and Dysteriidae (Dysteria balani sp. n.). Apostomatida are represented by Askoellidae fam. nov. with the genus Askoella (A. heliostoma sp. n.), considered as neotenic apostome tomite with a secondary mouth, its ciliature has derived from thigmotactic kineties. Rhynchodida are represented by Сrateristomatidae fam. nov. with Crateristoma kindi sp. nov., — a unique rhynchodid with constant swimming, wide opened mouth and very wide cytopharynx, modified thigmotactic ciliature; unlike all other rhynchodids, it is incapable for suction and ingests free-swimming ciliates like prostomes. Peritrichida-Sessilidea are represented by Epistylidae (Epistylis horizontalis Chatton, 1936). The feeding interrelations between commensals and their morphological adaptations are discussed.

Entomophthorous fungi are widely distributed in black-flies and are recorded all over the world. In the Luga region of the Leningrad district two species of entomophthorous fungi were found on adults Boophthora erythrocephala De Geer: Entomophthora curvispora Nowakowski and Entomophthora ovispora Nowakowski. Species of parasites well differ in their shape, size and the structure of conidium. The first species does not infest mature eggs and does not form mycellium on wings, rhe second species infest all internal tissues and wings. Females infested with entomophthorous fungi fly to the places of collective egg-clutches and perish on clutches laid by sound females. Perished insects fixed with rhizoids of fungi remain here till the development of parasite is accomplished. The description of various stages of the parasite's development and the process of formation of primary and secondary conidiums is given. The formation of spores was not observed.

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Summary is absent.