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The phenomenon of autogenity has been examined by means of different criterions both in nature and in laboratory in 25 blood-sucking species of the genus Culicoides, which were collected in Russia, Uzbekistan, Azerbaijan, Armenia, Georgia and Kazakhstan during 1979 — 1990 years. An autogenetic maturation of eggs has been observed in 6 species, and the absence of this phenomenon has been observed in 19 species. It is suggested, that autogenity or non-autogenity is a species characteristic of blood-sucking midges. The processus of autogenetic vitellogenesis takes the time from later pupa (more than 2 days of this stage) to earlier imago (lesser than 2-3 days of this stage).

The study of the vector-agent model (Anopheles sacharovi — Plasmodium gallinaceum) has shown that the development of ovaries of the vector stimulates its receptivity to the malaria agent. In the case of braking of follicule development the mosquitos were nearly not infected. The capability of mosquitos to be infected without previous carbohydrate feed is confirmed. The influences of the age of mosquitos and the quantity of blood soaked up on the egg development and on the receptivity to malaria agent are demonstrated.

Two new species of the genus Neotrombicula Hirst, 1925 are described from Western Caucasus. Neotrombicula alexandrae sp n. is similar to N. autumnalis (Shaw, 1790) but differs from it by several measurable characters and by sensillae barbed only in distal half. N. abagoensis sp. n. slightly resembles N. autumnalis and differs from it by significantly greater value of the majority of standard measurements, NDV and by more thick barbs of D. Specimens of new species were collected on rodents near the towns Maikop, Anapa, and in the area of the Caucasian reserve. All holotypes and paratypes of new species are deposited in the Zoological Institute, Russian Academy of Sciences (Saint-Petersburg).

Free-living in stars of three trypanosomatid species, namely Crithidia fasciculata, Blastocrithidia gerridis and Leptomonas jaculum, have been examined by means of light and electron microscope. The time of surviving in the water has been discovered for these instars in experiment. Times of surviving were as follows: B. gerridis — 72 hours, L. jaculum —96 and C. fasciculata — 168 hours. Similarities of free-living disseminating instars of tripanosomatids to cyst-like amastigotes and endomastigotes and also differences from these ones have been demonstrated.

It has been shown that an increase of virulence of Leishmania major, L. tropica, L. braziliensis as a result of passing through animals and its decrease during the cultivation are accompanied by certain changes of biochemical characteristics of these promastigotes. In the former case the activity of NADP-H-diaphorase and peroxidase of promastigotes and their ability to be transformed into final (invasional) metacyclic forms increase and in the latter case these characteristics decrease. The level and duration of virulence in culture depend not only on absolute value of the above-mentioned characteristics but also on the graduality of their change. Metacyclogenesis and activity of oxidative enzymes are suggested to be the correlates of virulence of various Leishmania species.

Suckling rats were used as a model host for our previous EM studies of the endogenous development of Cryptosporidium parvum isolated from spontaneously infected calves (Beyer e. a., 1990; Beyer, Sidorenko, 1990). In the course of repeated infections it was noticed that the oocysts discharged by the recipient host (rat) were obviously larger than those in the donor's (calf's) isolates. Keeping in mind the presumable taxonomic significance of coccidian oocysts as a constant and rather reliable tool for species discrimination we made a comparative quantitative and statistical analysis of the mean values of oocysts of C. parvum, originating from several sources (table 2): a random human isolate (N1), several random isolates from spontaneously infected calves (N 2—5), isolates from calves (N 6—8) used as the infecting material for suckling rats, and fecal samples from the experimentally infected rats (N 9—15). The results obtained have shown that the oocysts discharged by rats (N 9—15) were larger that those of calf origin (N 6—8), with the differences being statistically significant with 95% confidence. Besides, within the same host (rat) at least two oocyst groups were distinguished (N 9—11 and 12—15, resp.) whose differences in mean values also appeared statistically significant. The larger oocysts displayed differences in morphology bearing distinct walls which were never observed either in the donor isolates or in the smaller population of the recipient oocysts. The established differences in oocyst dimensions lay presumably within the frames of the normal reaction of C. parvum and other Cryptosporidium species, due to biological peculiarities of unusual life cycles of these unique coccidia: their homoxenous (i. e. confined to one host body only) development is combined with polyxeny (i. e. a wide host specificity that involves the number of host species representing different environmental conditions). The parasite's ability to change its functional morphology and size may appear some kind of preadaptation to the number of varying conditions met by these polyxenous coccidia. This and other relevant assumptions are discussed in the paper.

The new species of myxosporidia, Zschokkella admiranda sp. n., is described from Mugil cephalus (Mugilidae). Also, 4 species of myxosporidinns are recorded as a new for the fauna of Black Sea. New hosts are recorded for 6 species of parasites. Original figures provide 9 species of myxoporidians.

During the study larvae of insects living in the river Ucha several species of parasitic protozoans have been found as follows: three species of gregarines — Asterophora elegans Leger from Phryganea grandis L. (Trichoptera), Asterophora sp. from Hydropsiche pellucida Curt. (Trichoptera), Botriopsides ovalis sp. n. from Rhantus sp. (Coleoptera); six species of microsporids — Amblyospora sp. from Procladus culiciformis L. (Diptera), Parathelohania sp. from Anopheles maculipennis Mg., Vavraoa sp. and Thelohania sp. from Simulium sp. (Diptera), Amblyospora sp. from Anabolia sp. (Trichoptera), Nosema sp. from Cloen dipterum L. (Ephemeroptera); and also flagellata Leptomonas sp. from Gerris lacustris L. (Hemiptera).

Changes of lactatedehydrogenase (KF 1.1.1.27) activity have been studied in the liver of the bream been infected with plerocercoids of the cestode Digramma interrupta. It is showed, that an increase of enzyme activity depends upon a slowly migrating form LDH-6. Problems of interaction at the level of substrate within a system parasite — host is considered.

This report provides the data on diploid and haploid chromosome number and structure of karyotypes of 230 species of trematods. Also, it presents here original author's materials on peculiarityes of chromosome sets of 88 trematode species, most of which have been studied for the first time.

A modified trap for quantitative estimations of blood-sucking insects is described. It is shown, that this trap has a number of advantages. Technical description, recommendations on constructing and exploitation are provided.

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