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The analysis of available data on the structure of mouthparts, salivary glands, and behavior in two main groups of hard ticks (Prostriata and Metastriata), and also of molecular-genetic data revising the origin of hard ticks from new point of view, allowed the author to propose a hypothesis of the secondary character of male aphagia in representatives of the subfamily Ixodinae (genus Ixodes). Positive aspects of this phenomenon that had stipulated the evolutionary success of this subfamily, comparable with that in other representatives of othe hard tick genera (group Metastriata).

Fleas, temporary ectoparasites of mammals and birds, are important objects of epidemiology and zoogeography. Being associated with the host body only during certain period of their life cycle, they are influenced by temperature and humidity conditions of the environment. In this regard, the distribution of many species does not coincide with that of their hosts and requires special research. Our goal was to characterize the fauna of fleas of mammals and birds in the Steppe Podonye (Don Basin valley), the Lower Volga region, the Northwestern Caspian Region, the Pre-Caucasus and on the northern slope of the Greater Caucasus. Fleas of most species parasitize there on a wide range of hosts, including representatives of different genera, subfamilies or families. Parasites of 57 species are distributed in the corresponding biotopes throughout the territory of Southern Russia. Several species live in plain and are not found in the Greater Caucasus; others, on the contrary, live only in mountains.

The article presents the results of a faunistic assessment of the population of blood-sucking mosquitoes in the regions of Azerbaijan located in the south-eastern part of the country. Mosquitoes were caught in five settlements of the Lankaran District (Lankaran, Shirinsu, Urga, Goyshaban, and Kanarmesha), in five settlements of the Masally District (Masally, Mahmudavar, Eminli, Akivan, Miyanku) and in 5 different sites of the Gizil-Agaj Nature Reserve. 155 mosquito samples were collected during the entire work, with the total number of collected mosquitoes constituting 5422. 26 species were identified, among which C. pipiens was the most abundant. Three species (Aedes cataphylla, Aedes dorsalis, and Orthopodomyia pulchripalpis) were not previously recorded in the fauna of the studied region, and also 3 species (Aedes aegypti, Aedes albopictus, and Culex apicalis) were identified for the fauna of the South and North Caucasus for the first time. The revealed widespread distribution of mosquitoes necessitates a more advanced study of its causes, being necessary to control their possible participation in the transmission of arboviruses.

Ixodid ticks communities in Primorsky Territory are characterized by a significant diversity of species. The species richness of the family is more completely manifested in the islands of Primorye than in the mainland. Bi- and polydominant ixodid communities are observed only in islands. Monodominant tick community was, however observed only in Putyatin Island of the eight islands surveyed in 1982-1983; the goal of the present work is to describe contemporary structure of hemi-populations of adult ixodid ticks in Putyatin Island. Ticks were collected from vegetation by flagging in May 17-21, 2021 at different locations in the island. The following species have been recorded in the island (in descending order of abundance): Dermacentor silvarum Olenev, 1932, Haemaphysalis concinna Koch, 1844, Ixodes persulcatus Schulze, 1930, H. japonica douglasi Nuttall et Warburton, 1915, I. pavlovskyi pavlovskyi Pomerantzev, 1946. In total, 354 individuals of ixodid ticks were collected. A low index of tick abundance was revealed. As a result of survey work in Putyatin Island in 2021, H. longicornis Neumann, 1901 was not found, I. pavlovskyi was registered for the first time, the abundance of D. silvarum increased significantly, and the abundance of I. persulcatus increased to a lesser extent. Possible causes of changes in the structure of ixodid tick communities are discussed. It has been established that bidominant complex of ixodid tick species is currently observed on Putyatin Island (D. silvarum 45.8% и H. concinna 33.3%), as well as in other islands of Primorsky Territory.

The ultrastructure of the tegument of encapsulated tetrathyridia of the genus Mesocestoides Vaillant, 1863 (Cestoda, Cyclophyllidea, Mesocestoididae) from the liver of root voles Microtus oeconomus (Pallas, 1776) and the structure of the three-layered capsule surrounding them were studied for the first time. Several types of extracellular structures were noted on the surface of the tetrathyridia tegument: vesicles, fine granular material, and vacuoles. Besides, the phenomenon of microtrichia shedding, which have expanded parts, was found. Host cells being in contact with extracellular material show signs of destruction. A characteristic feature of the capsules surrounding the tetrathyridia is the mesh structure of the fibrous layer containing both native and degenerating inflammatory cells.

The gamasid mites Gaeolaelaps debilis (Ma, 1996) (Acari: Mesostigmata: Gamasina) were found in the probe with bloodsucking diptera (Diptera: Ceratopogonidae, Culicidae, Simuliidae) from man in the Pskov region (Russia). The mites were known from beetles, soil and anthills before.

Parasitological examination of 597 small mammals caught by different means in Southern part of Baikal region, have been held. 4056 ectoparasites have been gathered from the mammals (fleas, lice, hard ticks and mites), species being identified for 1077 of them with two Ixodid species, three lice and 20 flea species. The estimation of ectoparasites infesting was held using traditional indices - parasite load and parasite occurrence. The arthropods have been found on 55.2% of the mammals, with 6.8 ectoparasites per one individual in average. Infesting with the mites was the most intensive, followed by fleas and lice. Ixodid ticks were found only on the animals trapped from May to September. There have been age and sex differences in infesting of specific groups of small mammals and parasites. Positive correlation has been found between animals weight and parasite load in Clethrionomys (Cl. rufocanus and Cl. rutilus) and negative correlation - in Apodemus speciosus.