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Malariological situation analysis in the USSR and world over testifies to increasing malaria incidence particulary in the countries where earlier it was almost fully eradicated. Malaria epidemics in these countries (posteradication epidemics) is a new phenomenon in malariology. Temporary success of the global campaign of malaria eradication has led to a deadlock in malariology which during the past 10 years is being successfully overcome. Achievements of modern malariology are reviewed in the article on three levels of the host-parasite relationships: a cell, organism and population. Particular significance of the research in malaria vaccines is emphasized.

1591 specimen of small mammals, 467 nests of those, 250 birds and 38 nests had been investigated in 1972—1977. 19 182 specimens of gamasoid mites of 41 taxon had been found. Morphological and ecological adaptations of two mass species, Haemogamasus ambulans and Hinstionyssus isabellinus had been studied.

Haller's organ in A. tridentatus consists of a capsule and an anterior group of sensilla. The capsule is the hollow in the cuticle on the dorsal surface of the first tarsus, where 4 pored hairs of olfactory sensilla are situated under the cover of the roof, formed by an anostomosis of the upper brunches of pleomorphs (capsule's bottom non-sensory cuticular outgrowths). The canal of the accessory ampullaceous sensillum opens in a capsule near the bottom. The anterior group of sensilla consists of two parts : proximal part, containing pored grooved and thin hairs, is homologous to the anterior grouf of ixodid ticks, and distal one which has no homologues in ixodids. Fine structure of all the sensilla in the mentioned parts of Haller's organ is described in detail.

New species of chiggers from Tadzhikistan are described: Leptotrombidium tamanta sp. n. differs from all other species in having pubescent dorsal and lateral setae on the tibia of palps; L. derlatkoi sp. n. and L. apertum sp. n. are similar with L. smirnovi Kudryashova et Ribin, 1974, from which the former differs in having in the first dorsal row 8 setae instead of 10 and in certain sizes and the latter — in having a smaller number of setae on the body, short barbs on the dorsal setae and sizes. L. solum sp. n. differs from the close species L. europaeum (Daniel et Brelih, 1959) in the number of dorsal setae (43 instead of 34), their location and smaller sizes of the scutum. L. wolandi sp. n. differs from the preceding species by a greater number of NDV and shorter PL. L. multiplex sp. n. is characterized by a great number of setae on the body (104—120). L. smirnovi is first reported from Tadzhikistan.

It has been established experimentally that the fecundity of females of Xenopsylla gerbilli minax is wavy in its character from the beginning to end of their reproduction (peaks are replaced by falls). In spring and summer the egg laying proceeds on the 2nd—3rd day after the first bloodsucking of fleas and lasts to the end of their life. In autumn the first eggs develop on the 4th—6th day and do not develop at all at the end of the life. In winter months the egg production is somewhat slowed down but with the coming of spring become more intensive. Progeny obtained from one female during the experiment varied, depending on the conditions of the maintenance, from 20 to 130 individuals.

In infected fleas the agent of intestinal yersiniosis underwents a complex cycle of quantitative changes after each feeding. A species belonging of blood consumed greatly affected the dynamics of the agent abundance. The general peculiarity of the development of microbes in insects, which fed on various animals (white mice, Sirian hamsters, white rats and guinea pigs), is characterized by the decrease in the abundance of the agent during the first hours after feeding. This was followed by an active multiplication of microbes replaced by a new fall after which the abundance maintained on the level close to the initial one. A comparison of obtained results with the data on the digestion in fleas has shown that the phases of the primary dying off and depression of the agent falls within the intensive-decay of the food clot. The active multiplication proceeds at the end of digestion that may be promoted by the decrease in the fermentative activity and abundance of products of blood decay easily assimilated by microbes. The next fall in the agent's abundance and the absence of multiplication are associated with the exhaustion of the nutrient medium in the process of absorbtion and vital activity of microbes.

Seasonal changes in the female age composition of micropopulations of X. skrjabini are described. The descriptions are based on observations conducted within a period of 1971—1976. The comparison of females' age with the time of mass egg laying and the data on the developmental cycle rate (from egg to imago) suggests that in Mangyshlak fleas of X. skrjabini have four generations a year. The second, third and fourth generations parasitise at the end of summer or early in autumn. The third and fourth generations hibernate in the quiescence state, begin reproducing in the spring of the next year and in June give start of the first summer generation.

A new species of monogeneans, Euzetrema caucasica sp. n., from the urinary bladder of Mertensiella caucasica (Waga, 1876) is described. The new species differs from E. knoepffleri Combes, 1965 by greater sizes of the disc, median and marginal hooks and anterior suckers. Certain suggestions are made on the biology and life cycle of Euzetrema.

The fat-acidic composition of E. crassum and D. dendriticum was investigated. Lipids of E. crassum differ in greater unsaturation as compared to these of D. dendriticum as well as in greater amount of acids of type ω3, whereas acids of type ω6 and stearic acid were found in extracts of E. crassum in less quantity than in D. dendriticum. This phenomenon is characteristic of organisms living under conditions of low temperatures.

The organogenesis of Acanthocephalus lucii was followed and its developmental periods established. In the organism of the intermediate host Asellus aquaticus the larva of A. lucii has three developmental stages: acantor, preacantella and acantella. At the average daily temperature of 25° the developmental period from the egg to acantella completes within 19 days, at 22° — in 32 days, at 19° — in 51 days, at 18° — in 60 days, at 15 — 16° — in 72 days and at 15° — in 89 days. In the intestine of fishes the worms become mature in three weeks after the infection. The excretion of eggs by females into the environment begins in 36—39 days after the worms have reached sexual maturity. The whole development of the worm in the definitive host lasts 57 to 60 days.

For the first time the description of the IInd and IIIrd stage larvae of C. cirratus from the submucous membrane of cod fish is given and the possibilities of the direct life cycle of C. cirratus are discussed. The scheme of the life cycle of C. cirratus is as follows. Eggs come out into water with faeces of the host at the stage of 2—4 blastomeres. 10— 14 days after this the 1st stage larva hatches. After 4—5 days the Ist stage larva converts into the IInd stage by undergoing the first moulting. With food the IInd stage larva enters the stomach of cod fish. There it penetrates the submucous membrane of the stomach and converts into the IIIrd stage larva. After that the IIIrd stage larva migrates into the intestine where it undergoes the IIIrd and IVth moultings and reaches the adult stage.

The territory of Karelia was investigated from 62° to 66° N. In the nests of Riparia riparia the tick Ixodes lividus at all active phases of its development was first found. On the northern border of its distribution area the species shows a tendency to hibernate at the phases of nymph, female and male. This ability has favoured to a considerable extent the advancement of the species into the northern latitudes up t° 66° N.

In Burjatia and Mongolia the infection of horses with rhinoestrosis and gastrophilosis accounts for 97.8—99.2% and 98.9—99.5%, respectively at the infection intensity 34 to 721 and 55 to 1473 larvae. The sheep botfly is represented by one and the horse botfly by six species; they have one generation a year. The flight of the horse botfly begins from the second decade of June and ends in the second decade of September; the flight of the sheep botfly begins in the third decade of June and ends in the first decade of September. The pupal stage lasts 20 to 61 days.

A new cestode species Amphicotyle ceratias sp. nov. (Amphicotylidae) is described. It was obtained from the intestine of marine fish, Ceratias holboelli, in the Antarctic region.

A new trematode of the genus Paranematobothrium triplovitellatum gen. et sp. n. from the body cavity of Scomber scombrus from the Indian ocean is described. The individuals of the new genus are not incysted. Testes paired, ovary twisted, unbranched, vitelline gland bifurcates, uterus forming three turns.

Acanthobdella peledina was first found in the basin of Lake Baikal on the fluvial form of the Baikal grayling Thymallus arcticus baicalensis and Coregonus lavaretus pidschian from the Upper Angara. Cystobranchus mammillatus, a parasite of burbot, is widely distributed in the tributaries of Baikal. The absence of these subarctic leeches from Baikal itself is explained by their rheophily.

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