470 MR. B. p. UVAE.OV ON THE CJEOGEAPHICAL DISTRIBUTION 



Manytch (which joined the Black Sea to the Aralo-Caspian basin), 

 it is necessary to conchide that the process of populating these 

 plains began after the drying xip of the above-named strait, and 

 the whole fauna of the Caspian Ciscaucasia should be regarded 

 as being of quite recent origin, which explains the absence of 

 some characteristic Kirghizian forms, as, for example, Armene 

 alata, Oxi/thesjns ttircomanice, Pyrgodera annata, etc. All above 

 considerations support the idea that the deserts of the Caspian 

 Ciscaucasia form a distinct zoogeographical district of the 

 Turanian province. 



As for the boundaries of this district, they are all well marked 

 except the southern one. This district occupies the clay and 

 sand}^ deserts adjacent to the lower currents of the rivers Kuma 

 and Terek, as well as the whole valley of the Manytch. I con- 

 sider the latter valley as the northern limit of this district, 

 while the western and south-western are determined by the 

 corresponding boundaries of the South-Russian and the Kuban- 

 Terek districts. The southern boundary, delimitating this 

 district fi-om the Caspian Transcaucasia, is yet unknown, and I 

 suppose it is not very sharply defined. 



14. The district of Western Caucasus (C.Oc). 



The Orthopteran fauna of the subalpine and alpine zones of 

 the western part of the main Caucasian chain includes 40 species 

 (24 A 4- 13L -|- 3 G). Amongst them a very striking group is 

 formed by 20 species of evident boreal origin, as follows : 



Tettix bipuiictata. Stenobothrus apricarius. 



„ subulata. *Gonipliocercus sibiricus caucasicus. 

 Parapleurus alliaceus. Arcyptera fusca. 



Chiysochraon dispar. *Mecostetbus grossus. 



„ brachypterus. *Psopbus stridulus. 



Stenobothrus nigromaculatus. *Podisma pedestris. 



* „ viridulus. *Locusta caudata caudata. 

 „ hsemorrboidalis. *Platycleis roeseli. 



* „ ventralis. *Decticus verrucivorus verrucivorus. 



* „ scalaris. *01ynthoscelis griseoaptera. 



The presence of these boreal species as well as the total absence 

 of representatives of Mantodea,, the small number of Gryllodea, 

 the poverty of QildipodidsB and Decticidte — this all gives to this 

 fauna a rather northern character. This character is further 

 strengthened by the remarkable fact that eleven, i. e. more than 

 half of the above-named boreal species (marked by an asterisk), 

 show a discontinuous range of distribution, their main (northern) 

 area being separated from the Caucasian one by a large space of 

 South-Russian steppes from which these species are totally 

 absent. As regards the way by which these boreal elements 

 came to the Caucasus there may be two different suggestions : 

 either they migrated via Balkania and Asia Minor, or reached 

 the Caucasus direct from the north at some remote time when the 



