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Two stocks of the European pilchard (Sardina pilchardus Walb.) from the Atlantic coast of Northwestern Africa were discriminated with the use of parasites as biological tags. A total of 646 fishes (TL = 15—25 cm; modal age 1—3) were examined for parasites in the area between 30—18 °N during 2005—2010 winter and summer seasons. Fourteen species of parasites were found. Mean prevalence constituted 62 %. The most abundant species (with prevalence 5 % in at least one of the samples) included Goussia clupearum, Ceratomyxa truncata, Cocomyxa morovi, Aphanurus stossichi, Lecitaster confusus, Bacciger bacciger, Hysterothylacium sp., and Anilocra capensis. All fishes were grouped into one-degree latitudinal groups. Analysis of parasite component communities in latitudinal groups allowed combining parasite component communities into northern (30—28 °N) and southern (24—18 °N) groups only in winter spawning season. These two groups correspond with two sardine stocks — "A + B" and "C" that were separated by FAO working group on the base of ecological and fishery data. Parasite component community of the stock "A + B" was characterized as balanced with dominant species B. bacciger. The parasite component community of the stock "C" was characterized as an unbalanced stock with Hysterothylacium sp. as the dominant species. Significant values of prevalence for G. clupearum A. stossichi, B. bacciger, Hysterothylacium sp., and A. capensis were revealed in fishes from stocks "A + B" and "C". These parasites may be used as biological tags that characterize specific of host-parasite complexes of northern and southern subareas examined.

Behavioral responses of Diplostomum chromatophora cercariae to light were studied in laboratory experiments. Cercariae demonstrated positive phototaxis that was especially pronounced during the first hour of cercarial free life in the environment. After 6 h, the photoreaction is weakened but it retains the character of positive phototaxis. The photo-orientation helps cercariae to localize themselves in the areas of the water body ("host-space") where contact with the second intermediate host (fish fry) is most likely. It is assumed that the increase of the locomotory activity in D. chromatophora cercariae under sudden shading or lighting should be considered as a case of manifestation of the "fixed behaviuor" trigged by abrupt changes in illumination.

The authors analyze different names of thoracic skeletal structures in mosquitoes (Dip-tera: Culicidae), used by various authors (Kirkpatrick, 1925; Edwards, 1932; Stackelberg, 1937; Sazonova, 1958; Belkin, 1962a, b; Maslov, 1967; Gutsevich et al., 1970; Knight, Laffoon, 1970; McAlpine, 1981; Becker et al., 2010). In the abovementioned publications, a small number of skeletal structures, morphologically very important for the identification of species and genera of the family Culicidae, are denoted by multiple synonymic names, while certain completely different skeletal structures are represented under a single homonymous name. Duplicated synonymic names for thoracic sclerites, setae, and scales on sclerites considerably hamper the work of specialists determining species of the family Culicidae. In some cases, this fact results in erroneous diagnostics of species. We provide a detailed description of the thoracic morphology of mosquitoes, pointing to existing synonymic Russian and English names for each skeletal structure and also recommend the use of a single Russian term for each structure.

The data on the distribution of 34 species of bloodsucking mosquitoes and on 42 horsefly species of the fauna of the northeastern Russian Plain are given. The analysis of the landscape and zonal changes in species diversity and their abundance was performed. Species diversity of these families increased northwards. Two borders of the fauna's depletion were discovered: at the border between the middle and northern taiga subzones (mosquitoes and horseflies) and at the border between the northernmost taiga subzone and the forest-tundra zone (horseflies only). The northern and southern boundaries of species ranges in the region are identified.

The fauna of ectoparasites of the particoloured bat (Vespertilio murinus Linnaeus, 1758), the most common synanthropic bat in the Urals, is examined. The core of the ectoparasite fauna consists of temporary ectoparasites — gamasid mites belonging to the genus Steatonyssus. New findings of the poorly known species Steatonyssus superans are described.

A new trematode species, Gonocerca pectorali sp. n. was revealed in the collection of fish trematodes from the Pacific Ocean (Kuril Islands region). A brief review of publications on the species composition of the genus Gonocerca is given and points of view of some researchers on the genus structure were analyzed. The description of G. pectorali is given together with the differential diagnosis of the new species and the discussion on its position in the structure of the genus.