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The present state of parasite population biology is reviewed with special reference to parasites of fish. Mathematical models have provided a coherent body of theory which is supported by many laboratory investigations. There is nevertheless some disagreement between predictions based on this theory and data obtained from investigations of natural parasite populations. It is suggested that this is partly due to the oversimplifications and limitations of the models, and partly to the unsystematic approach of many field investigations and the resulting shortage of data of the right sort. In freshwater habitats disagreement may also be due to the rapid and extensive changes that are taking place in the habitats themselves as a direct consequence of human activities. Future developments should involve models becoming more realistic, and field investigations being conducted in a more systematic and analytical manner in order to obtain quantitative measurements of the essential population parameters.

Analysis of the fauna and distribution of haemosporidia of the genera Leucocytozoon and Plasmodium found in blood of 2605 examined birds of 86 species is given. The fauna of parasites belonging to the genus Leucocytozoon is represented by 7 species. In passerine birds the species L. fringillinarum is dominant. Most malarial plasmodia found in blood of examined birds belong to the subgenus Haemamoeba. Difficulties arising during species differentiation of investigated groups of Protozoa are discussed.

Electron microscope observations were conducted to study changes in the cellular structure of IIId type alveoli of feeding females of I. persulcatus. Within the first 1—2 days of feeding granulosecreting glandular cells "d" and "e" get free of secretory inclusions. After that cells "d" degenerate completely and cells «e» undergo morphological transformations and start to fulfil osmoregulatory functions. From the third day of feeding cytoplasm of cells "e" and basal intersticial cells form a complex labyrinth from a system of branching processes limiting intercellular space from the basal to apical surfaces of alveolar wall. Cells "e" of I. persulcatus in their structure and functional activity closely resemble the earlier described cells "f" in alveoli III of the tick Rhipicephalus appendiculatus.

Only one species of ixodid ticks Ixodes persulcatus occurs in the forest-park zone. Conditions of foliage forests with high grass, where occur hosts of all developmental phases of ticks (elks, hares, rodents, insectivores), are most favourable for I. persulcatus. Preimaginal phases of I. persulcatus feed, in general, on dominant species (common shrew, redbacked and narrow-skulled voles, field mouse and northern birch mouse).

Seasonal distribution of C. tesquorum imagos in burrows of mountain souslik is regular in its nature. Their attachment to the host's body and to some elements of its living quarters in definite phenological periods is characterized by sufficient stability in different years. The above regularity can be used for improving the control of fleas in settlements of mountain souslik.

Two species of the subgenus Edwardsaedes, Ae. (Edw.) pingpaensis Chang and Ae. (Edw.) bekkui Mogi, are spread in the Palaearctic region, the first one being known from China only and the second one from Japan and South Primorye, USSR. The name Ae. (Edw.) antuensis Su, Wang et Li, 1965 should be considered as a synonym of Ae. (Edw.) pingpaensis Chang, 1965; the larva of Ae. (Ochlerotatus) sticticus Mg. has been erroneously described by Su et al. (1978) as larva of Ae. antuensis. The differential diagnosis of the females, male genitalia, and larvae of mosquitoes Ae. pingpaensis and Ae. bekkui, is given. The description of the fourth stage larva of Ae. bekkui from the South Primorye is presented for the first time in the home literature.

The specific composition and number of midges in nest biotopes of birds of forest formations of Western Sikhote-Alin are given. 17 species of the genus Culicoides were found to attack 17 species of birds during the nesting period. The number of midges in nests depends both on the biotopical distribution of nests and mode of living of birds and on the total number of midges in nature. The most high percentage of females engorged with blood at nests was recorded in the obsoletus group, which is most abundant on man and at nests of birds of anthropogenic complex.

Oncomiracidium of diplozoids has several large germinative cells which are homologous to those in miracidia of trematodes and oncospheres of cestodes. In diplozoid larva settled on the gills the trace of these cells is lost. Young diporpa has a ventral sucker, dorsal tubercle and hermaphroditic common genital anlage from which the anlage of uterine canal goes to the above sucker. Later on it disappears and anlage of testicle forms from the common genital anlage. In concreted diporps at the stage of separation from the genital anlage of ovary the uterine duct is formed anew. Vitelline duct and vitelline follicles are laid in the anterior part of the body independently of the common genital anlage. Spermathecal vaginalike duct is the latest anlage in the species in question.

Asymphylotrema macracetabulum (Belous, 1953) c. n. is described and diagnosis of the new genus Asymphylotrema in the subfamily Asymphylodorinae (the fam. Monorchidae) is given. The life cycle is studied and morphological characteristics of larval stages of this trematode in intermediate (freshwater molluscs Valvata sibirica and V. amurensis) and additional (Planaria sp.) hosts is given.

Peculiarities of the surface architectonics of the egg shell in 18 species of capillariids (Nematoda, Capillariidae) were studied. Capillariids were found in mammals of 5 orders: Insectivora, Chiroptera, Muridae, Carnivora and Arctiodactyla. A correlation between the structure of the external surface of egg shell of these nematodes on one hand, and localization in the organism of the definitive host and its biology on the other, was established. On the basis of these characters capillariids of the genera Capillaria, Eucoleus, Calodium, Liniscus, Thominx and Scrjabinocapillaria were arranged into 6 groups: 1 — the genus Capillaria (luman of the stomach and gut), 2 — the genus Eucoleus (mucous membrane of oesophagus and stomach), 3 — the genus Calodium (parenchima of the liver), 4 — the genus Liniscus (urinary bladder), 5 — the genus Thominx (lungs), 6 — the genera Thominx and Scrjabinocapillaria (lumen of the stomach). The classification suggested makes more precise and supplements the known systems of nematodes of the fam. Capillariidae.

The sensory system of two species of cercariae of the genus Cryptocotyle, C. concavum and C. lingua, is described and differences are indicated in the location of sensillae of both species which make possible the clear differentiation of both species.

The paper presents results of experimental studies of the effect of Allantonematidae on the reproduction of fleas. It has been established that the pairing of non-infected females with males infected with nematodes reduces the fecundity rate while the pairing of non-infected males with females infected with nematodes causes a complete stopping of reproduction of laboratory population. The conclusion was drawn on the role of allantonematides in the regulation of abundance of fleas of rodents in nature.

Summary is absent.

Summary is absent.