Larval identification of species and subspecies of the genus Hyalomma (Acari: Ixodidae) from Russia and neighbouring territories

The following species and subspecies of Hyalomma Koch, 1844 are recorded from Russia and neighbouring territories, including those involved in natural foci of tick-borne diseases: H. (Hyalomma) aegyptium (Linnaeus, 1758), H. (Euhyalomma) dromedarii Koch, 1844, H. (Euh.) asiaticum asiaticum Schulze et Schlottke, 1930, H. (Euh.) asiaticum caucasicum Pomerantzev, 1940, H. (Euh.) asiaticum kozlovi Olenev, 1931, H. (Euh.) anatolicum Koch, 1844, H. (Euh.) excavatum Koch, 1844, H. scupense Schulze, 1918, H. (Euh.) marginatum marginatum Koch, 1844, H. (Euh.) marginatum turanicum Pomerantzev, 1946, and H. (Euh.) marginatum rufipes Koch, 1844. The geographic distribution and host-parasite relationships of each taxon are discussed. Species characters of the larval stage, that can be distinguished using light microscopy, are found to be very few. These characters include shape of scutum, shape and rate of hypostome denticulation, shape and rate of the development of spurs on coxae I to III. Measurements of some morphological structure and their rations show statistically significant differences between some closely related species, even if qualitative discriminating characters are unknown. Only measurements and their ratios can be used for the discrimination of larval H. anatolicum from larval H. excavatum, because qualitative discriminating features have not been found for these species. The complex structure of the subspecific morhological differentiation of all parasitic stages in the polymorphic species H. asiaticum and H. marginatum is revealed. This structure probably reflects some peculiarities of the microevolutionary processes. Identification key for the larval stage of seven Hyalomma species is provided.