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The evolution of animal parasitism in mites of the infraorder Eleutherengona (Prostigmata) is discussed. Parasitism has arisen independently in numerous phyletic lineages or superfamilies of this infraorder. Mites of the family Pterygosomatidae are parasites of terrestrial arthropods and lizards, and species of Myobiidae are exclusively associated with placental and marsupial mammals. Most families of the superfamily Cheyletoidea comprise permanent parasites of vertebrates, and mites of the sister families Cloacaridae and Epimyodicidae, whose phylogenetic relationships with other eleutherengones are unknown, are endoparasites of turtles and small mammals, respectively. Moreover, some families of the diverse cohort Heterostigmata include insect parasitoids or true parasites of insects. Some phylogenetic lineages, such as Heterostigmata and Cheyletoidea, present a series of life forms transitioning between free-living predators, nidicolous predators, fungivorous mites, and, finally, highly-specialized ecto- and endoparasites. The representatives of some phylogenetically distant eleutherengone lineages developed similar adaptations to predation and parasitism. However, in spite of some similarities in these adaptations, the evolutionary trends and pathways for switching to a parasitic mode of life are quite different in particular eleutherengone lineages. With a few exceptions, each eleutherengone lineage is associated with a particular host group. Temporary parasitism by the larval stage only, a life-history pattern characteristic of the Parasitengona, does not occur in these mites, and all active stages are parasitic and live on host, except for the cheyletid tribe Chelonotini where only adult females are parasites. Species in most eleutherengone lineages that parasitize hosts of particular groups are mono- or oligoxenous parasites, and, therefore, good potential models for co-phylogenetic studies. Mites of the family Pterygosomatidae are permanent parasites of lizards and various arthropods that typically live in concealed habitats. This family represents the only example of mites belonging to one exclusively parasitic eleutherengone group occurring on both invertebrate and vertebrate hosts. The most probable explanation of the occurrence of this family on such varied host groups is host switching. It is hypothesized that Pimeliaphilus-like mites parasitized different arthropods living in concealed spaces and switched to parasitism on lizards that sought refuge in similar spaces. This host switch would have been ancient to account for the diversity of lizard parasites seen today. Mites of the family Myobiidae are ectoparasites of small marsupial and placental mammals. The development of effective structures for attaching to mammalian hair, primarily involving the first pair of legs, has increased in complexity during myobiid evolution. The subfamily Xenomyobiinae includes a single species Xenomyobia hirsuta parasitizing the Peruan marsupial Lestoros inca. Legs I of this species are only slightly modified. Mites of the subfamily Archemyobiinae, tribe Archemyobiini parasitize other South American marsupials. In these mites, the genua of the female legs I bear paired ventral clasping organs. Mites of the tribe Australomyobiinae parasitize Australian marsupials. The last tribe and all other myobiids belonging to the subfamilies Protomyobiinae and Myobiinae have an unpaired attachment organ on genu I. The subfamily Protomyobiinae is separated onto 3 tribes. In more derivative members of the tribes Acanthophthiriini (parasites of bats), Protomyobiini (parasites of "insectivores"), and in all Elephantulobiini (parasites of elephant shrews), the tibia and tarsus of legs I are fused apically. Mites of the subfamily Myobiinae parasitize rodents and are the most morphologically specialized, with 3 apical segments of legs I fused. Basing on the wide distribution of myobiid mites on mammalian taxa, it could be concluded that the origin of parasitism occurred in these mites not later than in the Lower Cretaceous, the assumed time of divergence of marsupial and placental mammals (Carroll, 1993). The host associations of the superfamily Cloacaroidea is still unresolved problem. Mites of this superfamily show a high level of host specificity; however, cloacaroid families and subfamilies are associated with phylogenetically distant lineages of vertebrates, turtles (Cloacarinae), birds (Pneumophaginae), and mammals (Epimyodicidae). The common ancestor of cloacarines may have become associated with turtles before the late Triassic. We believe that parasitism of Pneumophagus bubonis, the single species of Pneumophaginae, in the lungs of Bubo virginianus (Aves: Strigiformes) is a result of an ancient host shift following predation by some birds on live or dead turtles. All 4 currently known species of the Epimyodicidae are endoparasites in the subcutaneous tissues of voles (Rodentida: Cricetidae), moles, and shrews (Soricomorpha: Talpidae and Soricidae). The sister relationship between Cloacaridae and Epimyodicidae could reflect parasitism by their common ancestor on archaic amniotes before the divergence of the Synapsida (ancestors of mammals) and Diapsida (ancestors of turtles and birds). On the other hand, the ancestors of epimyodicids, retaining some features of their free-living ancestors, could have switched from diapsids onto synapsids considerably later.

Critical analysis of the taxonomy problems in the mosquito family Culicidae has been carried out. Different conceptions on the family classification are considered in historical aspect. Debatable points of the systematics of tribe Aedini are expounded. Recommendations on the use of names of mosquito taxa and annotated checklist of the Culicidae species from the fauna of Russia are given.

Nine mosquito species from the genera Culex, Culiseta, and Coquillettidia are found in the Novgorod Region as a result of eight-year investigation (1997—2004). The species Culex torrentium is for the first time recorded in the Novgorod Region.

Internal anatomy of the female Syringophilopsis fringilla (Fritsch, 1958) was investigated by light microscope using electron microscope to control the results for some body regions. The digestive tract is open. The anterior midgut includes the stomach and two pairs of caeca. The posterior midgut is represented by a long tubular excretory organ being connected to the stomach via a small opening. The opening is provided by a muscular sphincter. The short hind gut ends in the anal opening at the terminal side of the body. The unpaired tubular gland occupies medial region of the body between the brain and the mouth parts. Paired coxal glands lack typical sacculi. Each of them, in addition to long filtering tubules, contains two glandular regions producing different secretory products. The cuticul-lined excretory duct of each coxal gland opens into the podocephalic canal, running from the base of leg coxae I to the front side of the rostrum The female reproductive system of S. fringilla is composed of the unpaired ovary, large oviduct, and cuticular vaginal cavity with extensively folded walls. Vagina leads to the separate opening, situated in the deep body invagination ventrally to the anus. The oviduct consists of highly folded proximal portion and enlarged distal one. The distal portion of the oviduct is characterized by the glandular epithelial lining producing special secretory product into the lumen of the organ. All females examined contain numerous long spermia inside the large receptaculum seminis. The latter runs into the oviduct at the junction of its two parts. Large granulocytes were observed in the body cavity of the mites. Neither nephrocytes nor typical fat body cells were found.

Monogeneans parasitize 31 gudgeon species of 130, and 13 gudgeon genera of 30 known. Monogenea from gudgeon comprise 48 species of the genus Dactylogyrus, 1 Bivaginogyrus (Dactylogyridae), 18 Ancyrocephalus s. l. (Ancyrocephalidae), 6 Gyrodactylus (Gyrodactylidae), 3 Paradiplozoon, and 1 species of the genus Sindiplozoon (Diplozoidae). The following characters were used in the morphological analysis: 1) structure of the copulatory organ, 2) morphology of the anchors, marginal hooks and bars, 3) characteristic of attachment on gills. Among the Dactylogyrus species parasitizing gudgeon, 30 monophyletic species groups and 13 levels of morphological organization were established. The first level comprises dactylogyrids without the additional ventral bar of haptor. It includes species with the copulatory organ of pro-cryptomeres type. This type is ancestral for dactylogyrids of the Amur/China fauna. Levels II—IV; VI, etc. are derivates of level I. Levels VII—VIII can be characterized by the jamming type of attachment characteristic for Dactylogyrus sphyrna or D. anchoratus, when marginal hooks penetrate gill filaments towards the anchors. Levels IX—XII include species with the attachment by clasping, when the anchors directed towards each other. Some species groups of Dactylogyrus (V, XIII) switched onto gudgeons from other fishes (Cultrinae, Xenocyprininae, Hypophthalmichthinae). Species of the genus Ancyrocephalus s. l. form two levels of morphological organization and 8 monophyletic groups. Repeated switches of ancyrocephalids from freshwater gobies to gudgeons and their switches from gudgeons to other fishes were shown. Species of the genus Hemibarbus serve as hosts for morphologically peculiar species groups of Dactylogyrus and Ancyrocephalus s. l. We can conclude that gyrodactylids from gudgeons do not form a natural monophyletic group. This parasite fauna originated as a result of multiple switches from phylogenetically distant but ecologically similar hosts, for example sticklebacks, bitterlings, chars, spined loaches, etc. Species of the family Diplozoidae parasitizing gudgeons may invade also many species from other fish taxa.

Three nematodes species for the family Trichodoridae, Trichodorus similis, T. primitivus, and Paratrichodorus teres, vectors of Tobacco Rattle virus (TRV), have been found in the vicinity of Moscow. Frequency of the joint occurrence of the above species and TRV infection was 73%. Trichodorids occurred more often in agrocenoses, where their frequency of occurrence in some years was 50% in potato fields and 25% in barley fields. The effects of the environmental factors (soil type, pH, and soil texture) on the distribution of trichodorids and seasonal dynamics of P. teres are established. A high level of the infection with TRV, against the background of complex viral infections, in plantings of different potato breeds in revealed.

Fauna of blackflies from the Altai Republic was investigated, four species were recorded. One new species, Sulcicnephia stekolnikovi sp. n., is described. Two species are for the first time reported from Western Siberia.