Revision of the family Dolichocybidae ( Acari : Heterostigmata ) from the collection of V . D . Sevastianov

The dolichocybid mites in the collection of V.D. Sevastianov, namely Pavania riparia Sevastianov, 1980, P. tadjikistanica Sevastianov, 1980, P. protracta Sevastianov, 1980, P. tahanae Sevastianov and Abo-Korah, 1985 and Dolichocybe firjusae Sevastianov and Chydyrov, 1994, are revised and redescribed based on both the type and additional materials. An updated key to species of the genus Pavania is provided. The taxonomic position of Pavania protracta and P. tahanae is discussed.

The main aim of this article is to provide redescriptions of dolichocybid mites described by V.D. Sevastianov and co-authors based on type and additional material.

Materials and methods
The type materials of dolichocybid mites were loaned from the collection of the Odessa I. I. Mechnikov National University Museum of Zoology, Odessa, Ukraine. Additional material of Pavania riparia was collected by junior author on the dung beetle Copris lunaris and mounted in Hoyer's medium. One non type material slide of P. riparia from the collection of the junior author was remounted and several specimens were removed, dusted with gold and scanned with aid of a JEOL-JSM-6510LV SEM microscope.
Mite morphology was studied using a Carl Zeiss AxioImager A2 compound microscope with phase contrast and DIC objectives. Photomicrographs were taken with an AxioCam ICc5 digital camera. The terminology of the idiosoma and legs follows Lindquist (1986); the nomenclature of subcapitular setae follows Grandjean (1944). All measurements are given in micrometers (μm). For leg chaetotaxy the number of solenidia is given in parentheses.

Remarks
The holotype and paratypes available for study are in poor condition and redescription is based on additional material collected by the junior author.

Female (Figs 5-7)
The holotype and two paratypes available for this study are in rather bad condition (Fig. 7) and some tiny structures like cupules, dimples of dorsal plates and weak barbs on setae are not discernible. Length of idiosoma 120, width 80.

Discussion
The main differences between the genera Dolichocybe and Pavania according to Cross (1965) are the shape of cheliceral stylets (falcate and well developed in Pavania and small, indistinct in Dolichocybe) and position of palps (palps arising ventrolaterally in Pavania and laterally in Dolichocybe). In fact, the position of palps is rather uniform in all dolichocybid mites and can not be used as a generic-level character. The shape and size of stylets are also highly variable. In typical Pavania (like most species associated with dung beetles), stylets are really large and falcate. In typical Dolichocybe (D. keiferi, D. subcorticalis Khaustov, 2006, D. sibiriensis Khaustov, 2017 stylets are small and indistinct. However, at least in Pavania protracta and P. tahanae, size of the cheliceral stylets is intermediate between typical for Pavania and for Dolichocybe. Therefore, the shape of cheliceral stylets is a vague character, difficult to use in separation of the genera Dolichocybe and Pavania. Rahiminejad et al. (2011) redefined the genus Dolichocybe and used the following characters to separate Dolichocybe from Pavania: "gnathosoma apparently longer than wide; chelicerae small and indistinct; tarsus I with 10 or 11 setae; tibiae III and IV with one minute solenidion each; with deep constriction between propodosoma and hysterosoma separated by soft and transversely striated cuticle" (in Dolichocybe); "gnathosoma almost as long as wide; chelicerae large and distinct; tarsus I with 11 setae; tibiae III and IV with no solenidia; without deep constriction between propodosoma and hysterosoma" (in Pavania). Based on our study, the number of setae on tarsus I is the same in Pavania and Dolichocybe and can not be used in separation of these genera. The presence of solenidia on tibiae III and IV in Dolichocybe is also problematic character. In fact, solenidia on tibiae III and IV are apparently absent in D. keiferi (type species) (Cross 1965), D. hippocastani Rack, 1967, D. picea Rack, 1967(Rack 1967, and absent in D. subcorticalis, D. sibiriensis (Khaustov 2006(Khaustov , 2017 and D. firjusae (present study). Potentially solenidia on tibiae III and IV are present in Pavania brasiliensis Mahunka, 1970, at least Mahunka (1970 depicted a tiny solenidion on the tibia III. Therefore, the presence of solenidia on tibiae III and IV also can not be used for separation of these genera. It is also difficult to understand the extent of constriction between propodosomal and hysterosoma. Two redescribed herein species, Pavania protracta and P. tahanae, have intermediate characters between Dolichocybe and Pavania: body shape is similar to that in Pavania (not strongly elongate), gnathosoma is rather small (as in Dolichocybe), cheliceral stylets are of medium size (intermediate), constriction between propodosomal and hysterosoma is not deep (as in Pavania). In addition, both of these species have unusually short -considerably shorter than tarsal claws -empodia on tarsi II-IV. Pavania tahanae also has solenidia on tibiae III and IV (like some "Dolichocybe"). Both species were collected in soil (not phoretic on insects) and potentially could represent a non-phoretic form of Pavania/Dolichocybe complex. At present female dimorphism has been evident only in the genus Formicomotes Sevastianov, 1980. Non-phoretic form of F. heteromorphus Magowski, 1988 has much shorter empodia than phoretic form (Magowski 1988). In this paper, we retain all species in the genera in which they were originally described. The redefinitions of the genera Dolichocybe and Pavania are necessary based on redescription of their type species and more discoveries of new species in these two close genera (particularly Dolichocybe) are required (phoretic or in soil) to see what characters are more variable.