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The evaluation of the biomass of eggs and cercarians of some species of trematodes is done. It was shown that the summary mass of eggs entering biocoenosis exceeds considerably the biomass of adult trematodes; so the biomass of cercarians can amount to 50% of biomass of the infected part of mollusk population. The most part of eggs and cercarians is eliminated in biocoenosis by biotic and abiotic environmental factors and is included into biocoenotic trophic chains through eliminators or saprophags. When the main producers of useful production perform as eliminators, the organic substance contained in eggs and cercarians transforms into economically useful production. Such eliminators are the most perspective agents of biological control of pathogen helminths.

The detailed description of Botulus alepidosauri Guiart, 1938 from Thunnus obesus, Alepisauris ferox, A. brevirostris in tropical East Atlantic is presented. The described species is compared with literary data. Some changes were introduced into the taxonomic position of the genus Botulus, considered as a representative of the subfamily Botulinae in the family Hirudinellidae.

The cercomere of the larvae of Trichocephaloides megalocephala is formed exclusively by tegumentary tissues. The cytons of the tegument contain a great number of ribosomes, developed Golgi complex and numerous mitochondria that is indicative of the intensive synthesis, protein substances first of all. A distinct secretion of multivesicular membranes into subtegumentary space and further secretion of vesicles through the distal portion of the tegument into the external cyst cavity was observed. The main function of the cercomere is a production of the ground substance which apparently fulfils a protective function as it is suggested for glycocalix.

Studies were carried out of the nervous apparatus of Eubothrium salvelini, E. rugosumr E. crassum, E. vittevitellatus, Diphyllobothrium latum and D. dendriticum (Cestoda, Pseudophyllidea) at different stages of their life cycle. Scolexes of adult cestodes are innervated with 5 pairs of longitudinal nerve trunks, the number of which in the strobile gradually increases up to 17 pairs in species of Eubothrium and up to 60 pairs (in the widest parts of the strobile) in species of Diphyllobothrium. There were noted differences in of longitudinal trunks in different species and in the specimens of the same species but from different hosts, the width of the strobile being the same. The main lateral trunks are situated in the medullar parenchima. In species of Eubothrium they are wide apart while in Diphyllobothrium they are drawn closer to one another. The description of the rough and inner nerve plexuses is given. Judging by the larval developmental phases the well developed orthogon with 3 pairs of longitudinal nerve trunks can be taken for the initial state of the nervous apparatus in Pseudophyllidea. This means that the initial forms belonged to advanced turbellarians rather than to primitive ones.

In the northern part of the Amur district the life cycle of I. persulcatus and H. concinna lasts three, four and five years while that of D. silvarum — one year. The distribution of I. persulcatus and H. concinna further to the north is limited by an unsufficient heat for the development of eggs while for D. silvarum heat is not enough to complete its life cycle within a year.

The results of investigations of the activity of common species of the genus Aedes in south-western Bohemia in connection with meteorological factors, diurnal rhythm and specificity of investigated species are given.

18 species of black flies were registered from the north of the Amur district. It was found that the eternal frost affects considerably the species composition, abundance and phenology of black flies in this region. Prosimulium isio, Gnus cholodkovskii, G. rostratum and Schonbaueria subpusilla are bloodsucking species; of them G. cholodkovskii is most abundant. Data are given on the breeding places of bloodsuckers and seasonal dynamics of their flight.

On the basis of literary and the author's own data an opinion is suggested that the genus Leptoconops should be considered, as before, as the subfamily Leptoconopinae of the family Ceratopogonidae. The structure of the grooming organ of the hind tibia of Leptoconops is in general the same as in Culicoides.

Phenological observations on sand flies of the genus Sergentomyia inhabiting the burrows of Rhombomys opimus from the Karshinskaya steppe were carried out for many years. The emergence of two mass generations of S. arpaklensis and S. grekovi was noted for the spring-summer period. In S. arpaklensis from oasis the appearance of the first individuals was noted mostly often in the II—III decade of May, the first peak of abundance — in the II—III decade of June and the second peak of abundance — early in August. In S. grekovi the appearance of the first individuals was observed at the end of April—the very beginning of May, the first peak of abundance—in the second half of May and the second peak—in the first half of September. During July—August the abundance of S. grekovi is rather low. Throughout the desert areas southward from oasis all phenological phenomena take place in both species ten days earlier than in oasis. S. arpaklensis is characterised by its very high abundance in oasis and in foothill loes plain, sharp fluctuations in the abundance both in seasons and years and by the prevalence of females over males during the active flight.

On the basis of studies of age changes in the ovaries of Ct. orientalis, Ct. teres, C. laeviceps and X. conformis by means of luminiscent microscopy a scale was plotted for identification of physiological age of females of fleas. Depending on the presence or absence of yellow bodies and on the stage of development of oocytes in the ovary the fleas are arranged into two main groups: breeding and non-breeding females. According to the total combination of characters, size and colour of yellow bodies, presence and character of luminiscence in the germarium and adjoining areas of vitellarium, the presence of "starvation bodies", "degeneration bodies" and resorpting oocytes, the state of seminal receptacle, each group is divided into subgroups that enables us to make a detail description of age composition of the population under study.

A study was conducted on the fleas of P. scorodumovi and five local strains of the plague microbe, one of which is typical of the strains of the Altai subspecies and four are non-typical of this nidus. The fleas of this species are capable to transmit not only the plague agent of the strains typical of this nidus but also non-typical ones which differ in some biological properties and are avirulent for most carriers but Pallas's pika. Biological peculiarities of fleas of P. scorodumovi in addition to their high efficiency as vectors of the plague microbe enable us to associate the more active autumn epizooty with fleas of this species.

The RNA fraction and the intensity of their turnover in chick liver during experimental coccidiosis was studied. A marked (about 60%) increase of intensity of mRNA turnover with no changes in its amount was found. It was shown that pre-rRNA biosynthesis was significantly enhansed and, due to it, the amount of both pre-rRNA and mature 18S rRNA was increased while the level of 28S rRNA was unchanged. The relations between the observed changes of RNA biosynthesis and protein biosynthesis in liver in coccidiosis as well as the role of these changes in pathological process studied are discussed.

8 species of fishes from fishf arms of central and north—western regions of the USSR were examined. Chilodonella cyprini Moroff, 1902 and Ch. hexastichus Kiernik, 1909 were found. The reproductive process of infusoria was investigated. The data on the susceptibility of hosts of different species and age are given. The variability of Chilodonella depending on localisation and water temperature is shown.

14087 specimens of 26 species of gamasid mites were found in 52 nests of Apodemus sylvaticus collected in the vicinity of Odessa. The annual index of abundance of all species of gamasids is 270. The most abundant were Haemolaelaps glasgowi (53.9%), Eulaelaps stabularis (10.1%), Haemogamasus nidi (8.6%) and Hirstionyssus latiscutatus (7.2%).

14 species of mosquitoes belonging to four genera were recorded from the Kalmyk ASSR over the period of investigations from 1975 to 1976.

5 species of lice, Hoplopleura acanthopus Burm., H. longula Neum., Hoplopleura sp., Polyplax hannswrangeli Eich., Polyplax sp., were recorded from 15 species of small mammals of the Charskaya hollow, Kalarsky region, Chita district. H. acanthopus is most abundant and occurs on almost all species of small mammals.

Summary is absent.

Summary is absent.