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The data on interactions between pathogens of human diseases with natural focality in ixodid ticks (Ixodidae) with mixed infection are reviewed. Different variants of mixed infection revealed in nature and accompanied by predominantly extracellular, or both extra- and intracellular location of the agents in tick organism are considered. Natural mixed infection of ticks by different pathogens is a normal and commonly occurring phenomenon; moreover, there is no experimental evidence for the existence of any antagonistic relationships between spirochetes, rickettsias, and piroplasms in such ticks. The absence of antagonism between different agents in vectors largely provides a relative autonomy of corresponding parasitic systems and creates conditions for coexistence of different parasitic systems in mixed natural foci.

The horseflies of the genus Hybomitra flew out of artificial startpoints disposed on the lake surface with size about 1 km². At favorable weather conditions for a flight (17—22°, wind 0—1 m/sec, clouds 0—5%) the horseflies flew in the majority of cases to nearer shore lines. At lesser favorable conditions (16— 17°, wind 3—5 m/sec, clouds 60—100%) decreased the number of insects flying to far points of the lakeshore. Unfavorable conditions (16—17°, wind 5— 8 m/sec, clouds 80—100%) almost completely supressed the flight activity on the start points disposed over 100 m from the lakeshore. When the flight trajectories from start points to lakeshore were over 50 m in length the horseflies usually flew at 0.2—1.5 m above the water surface. These peculiarities of flight trajectories are probably caused by special functional mechanism, which ensure the optimal height the flight trajectories.

One of the possible functions of mosquito swarms is the intrasexual competition between males. It means that reproductive success of males with different phenotypes can differ. We compared the body size of males that emerged from two reservoirs situated near swarming site with that of swarming and coupled males. It was shown that mating in swarms lasted only 35—45 min in the middle of daily swarming period (fig. 1). The body size of males from different reservoirs differed significantly (fig. 2, a, б). The males of all size groups were found in swarms and pairs (fig. 2, в, г) though there were also present the males of larger and smaller size. The results indicate that male reproductive success in C. pipiens pipiens does not depend on male body size.

The argentophilic structures of metacercaries of four Microphallidae species of the "pygmaeus" group were investigated by the method of AgNO₃ impregnation. The argentophilic structures patterns in all four species investigated are similar. There are about 300—400 argentophilic structures at the surface of body of metacercaries. The classification of all argentophilic structures using the schemes by Richard or Bayssade-Dufour was impossible because of the large number of argentophilic structures and abscence of regular order in their arrangement. We could well identify the argentophilic structures of stylet, cephalic area and both suckers only. In spite of the similarity of the argentophilic structures patterns the interspecific differences were revealed. Both the arrangement and number of argentophilic structure were different. It was shown that argentophilic structures pattern may be used as species-specific feature. A comparison of argentophilic structures patterns in metacercaries and cer-caries of the "pygmaeus" group of some other Microphallus species was provided. The significant differences between these patterns were shown. Probably these differences may be supposed as ontogenetic differences between different stages of the life cycle.

Age changes of the parasite fauna in young daces was examined taking into consideration a host development and host drift. It was found out that the development of young dice parasite fauna under river conditions had some peculiarities. The first parasites of young daces are peritrichous ciliates; monogeneans and trematodes appear later. A portion in the parasite fauna represented by Gyrodactylus species is relatively high and that one of trematodes is low. With age the infection of daces at first increases and then it decreases, the infection peak is at the F stage of the host development. Unequal spatial distribution of the young dace parasite fauna is caused by the young fish drift and croocked form of the river bed.

The influence of the Ligula intestinalis plerocercoids onto the activity of digestive enzymes in the intestine of two different age groups (4+ and 8+) of the bream (Abramis brama) was carried out. The reliable descrease of proteinase and carbohydrase activities was observed in fishes of elder group and in cases of plerocercoid infection.

The influence of different concentrations of the natrium and potassium chlorides (0.001, 0.01, 0.1, 1, 10, 100, 1000, 10 000 mg/l) during 48 hours onto the fast behavioral and physiological reactions of the Lymnaea stagnatilis in a control and in case of the trematode infection was examined. Pathological reactions in infected individuals (with middle and heavy infection rate) are better expressed and appear earlier, protective ones are obliterated and appear later, than these form of reactions in noninfected molluscs.

The nature of potato population responses to the infection with the golden potato nematode Globodera rostochiensis was studied. The variability of host-plant parameters and the distribution of nematodes in dependence upon the initial infection rate have been shown.

The paper deals with the results of examination of 22 cultures of trypanosomatids from insects by the multilocus enzyme electrophoresis (MLEE). 10 isoenzyme systems were studied. Dendrogram derived from genetic distances is obtained. The results allow to confirm that the insects trypanosomatids have very low level of host specificity and do not demonstrate the dependence upon the place of culture isolation. The reality of genus Wallaceina was demonstrated. The genera Crithidia, Herpetomonas and Leptomonas were shown to be an artificial group. There is a good correspondance between the results obtained by MLEE, genome studying obtained by polymerase chain reaction with universal primers and kinetoplast DNA examination. The number of Trypanosomatid genera is not enough to reflect adequately the biodiversity of the group. The coincidence of data obtained by different methods as well as the presence of obvious clusters on the dendrograms allow to apply the classic taxonomic cathegories for classification of insects Trypanosomatids.

A new myobiid mite species Radfordia (Microtimyobia) cricetuliphila sp. n. (Acari: Myobiidae) from the striped hamster Cricetulus barabensis (Rodentia: Cricetidae) from Buryatia is described. The new species is closely related to R. (M.) triton Fain et Lukoschus, 1977 ex Tscherskia triton (Cricetidae). These two species are distinguished by characters as follows. R. (M.) cricetuliphila sp. n.: female — the setae sci, sce and l1 are 70—81, 63—67 and 51—60 long in 3 specimens respectively; male — the setae cxI1—2 are lancelate, 4 width, the setae ra are hair-like, the setae sci are 38—40 long in 3 specimens. R. (M.) triton: female — the setae sci, sce and l1 are 134, 90 and 11 78 long respectively; male — the setae cxI1—2 are hair-like, the setae ra are membraneous, the setae sci are 80 long. The new species group triton including 3 species — R. (M.) triton, R. (M.) abramovi Bochkov et Mironov, 1998 ex Phodopus spp. and R. (M.) cricetuliphila — is established within the subgenus Microtimyobia. All species of this group are ectoparasites of hamsters (Cricetinae). In females of this group the setae cxII1 are short, the setae d3, d4 are lanceolate; in males — the setae cxII1 are short, the genital shield with long apex. The species R. (M.) triton and R. (M.) cricetuliphila are closely related and represent typical species of the group, while R. (M.) abramovi differs well from both these species. The host genera (Tsherskia and Cricetulus) of these two myobiid species are also more phylogeneticaly related than either to the genus Phodopus. The fourth Radfordia species known from hamsters, R. (M.) cricetulus Fain, 1973 (the parasite of Cricetulus migratorius), is quite similar by the structure of male genital shield to Radfordia species commonly associated with voles (Arvicolinae). It is possible to suggest that R. (M.) cricetulus or its ancestor had an origin on voles and then migrated on hosts of the genus Cricetulus, namely on C. migratorius.

Summary is absent.