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Plague foci cover significant territories of all the continents, excluding Australia and Antarctica. They are distributed in eleven subregions of five zoogeographical provinces. Plague pathogen vectors include representatives of 346 out of 5937 species (about 6 %), 144 out of 1258 genera, 33 out of 156 families (about 20 %), and 9 out of 28 of orders (about 30 %) of mammals. Representatives of three rodent families (Cricetidae, Muridae, and Sciuridae) manifest the largest fraction of plague vector species (34 %).

The article summarizes, analyzes, and clarifies available information on horseflies of the south of the Middle Russian forest-steppe and related steppe territories located in the administrative borders of Belgorod and Voronezh Provinces of the Russian Federation and Kharkiv Province of Ukraine. In the region, 46 species and 1 subspecies of horseflies are noted. 15 species are limited in their distribution to the forest-steppe zone, 10 are steppe species, 22 species are widespread or penetrate into adjacent zones, finding suitable conditions there for development and habitat. The landscape-zonal structure of the faunal complexes of horseflies in the three regions is identical. The largest proportion is represented by forest and forest-steppe species (more than 60 %). The fraction of taiga-forest species in Voronezh and Kharkov Provinces is similar - 16 % each, in Belgorod Province, their fraction constitutes only 6 %. The fraction of steppe and semidesert species constitutes 25 % and 19% in Belgorod and Voronezh Provinces, respectively; in Kharkov Province, the fraction of steppe species constitutes only 12 %.

260 nymphs and the same number of adult of the taiga ticks Ixodes persulcatus collected from small forest mammals and vegetation in the southern taiga forests of the low mountains of the Middle Urals (Chusovskaya district of the Perm region) were investigated. Ticks (2 individuals in each pool) were studied by real time PCR (RT PCR) for the presence of Francisella DNA. 16S rRNA fragment gene (amplicon size 218-226) was detected in 70 of 130 nymph pools (53.8 %) and 50 of 130 adults (38.5 %). All positive samples were checked using species-specific primers and probes complementary to a fragment of the lpnA gene and the ISFtu2-element. The overwhelming majority of samples identified as F. tularensis: 60 of 70 nymph pools (85.7 %) and 49 of 50 adults (98 %). The obtained data indicate the possibility of the involvement of the tick I. persulcatus in the circulation of tularemia causative agent in natural foci of the forest type. There is a small probability of human infection by sucking adult of this taiga tick.

The infestation of bivalve mollusks with water mites of the genus Unionicola in the south of Western Siberia (Tyumen and Sverdlovsk Provinces) was studied. In Anodonta anatina, a single parasite species Unionicola aculeata was recorded. Indicators of extensiveness and intensity of invasion of this species was very high in lakes, however, parasites were not noted in rivers. In the mollusk Unio pictorum, recently settled into the water bodies of Western Siberia, no specific parasitic mites are currently recorded.

New data on the ability of volatile metabolites of entomopathogens Lecanicillium muscarium and Beauveria bassiana to change olfactory reactions and to participate in the regulation an amount of western flower thrips Frankliniella occidentalis are presented. The volatile compounds of the mycelium of two strains of L. muscarium showed a distinct repellency for larvae and adults with different preference indexes. The mycelium of B. bassiana strains under investigation caused a negative or neutral reaction of herbivore larvae. Repellent impact of L. muscarium mycelium on thrips females resulted in the decrease of the number of larvae of the next generation by 54 %, and the impact of the ethanol extract, by 78 %. Mycelial extracts of only 2 out 6 tested strains of L. muscarium demonstrated insecticidal activity against thrips larvae. The chloroform-methanolic extract obtaining from mycelium of strain Vl 21 was the most active - 74.7 % in 0.5 % concentration. The studied features of entomopathogenic fungi together with their toxic activity are theoretically and practically importance for the estimation of the potential of entomopathogenic fungi and their metabolites.

This work is the part of studies of the mercury bioaccumulation in helminths and fish conducted in 2006-2017. The high differences in the prevalence of plerocercoids of Ligula intestinalis in the different body length groups of cyprinids fish (bream Abramis brama and sichel Pelecus cultratus) were registered. The comparative analysis of the infected and non-infected fish resulted in the varied concentration of Hg both in plerocercoids of Ligula intestinalis and in muscles of intermediate hosts specimens - fish. On the other hand, there are the similarities of the mercury accumulation process between parasitised specimens of Abramis brama and Pelecus cultratus, caught at the different parts of the Rybinsk Reservoir (the Volga river basin). Mean value of mercury concentration in the plerocercoids Ligula intestinalis was 0.013 ± 0.005 mg Hg/kg fresh wet weight (0.001-0.043, with variation coefficient values Cv = 109.8 %). The levels of mercury was lower in muscles of non-infected breams in comparison with infected specimens: 0.073 ± 0.006 mg /kg (Cv = 39.0 %) and 0.094 ± 0.013 mg/kg (Cv = 40.5 %), respectively. On the contrary, in the sichel (Pelecus cultratus) - L. intestinalis cases mean concentrations of Hg were higher in muscles of non-infected fish (0.133 ± 0.008 mg Hg/kg, Cv = 36.4 %) than in infected by L. intestinalis specimens (0.092 ± 0.006 mg Hg/kg fresh wet weight, Cv = 16.4 %).

The paper contains new data about distribution of mosquitoes (Diptera: Culicidae) to biotopes on the plain (Yaksha) site of the Pechora-Ilych Reserve. The species composition of Culicidae in the reserve (23 species) and in the neighboring areas (11 species) was comparatively studied in 2016-2018. We identified two complexes of mosquito species as the Yaksha site of the reserve and the adjacent territories. The study sites demonstrated permanent links between the Culicidae species complexes and typical phytocenoses of the Pechora Rivver floodplain and valley.