448 MR. B. p. UVAROV ON THE GEOGRAPHICAL DISTRIBUTION 



may be. I hope these results will be of interest to every zoo- 

 geographist studying the distribution of animals in the southern 

 parts of the Palsearctic region. 



Before investigating more minutely the distribution of 

 Orthoptera in the territory under consideration, it is necessary 

 to give some information concerning the zoogeographical division 

 of the Palsearctic region based on my studies of this group, for 

 this division differs in some respects from those of other authors 

 founded on the distribution of other animal groups. 



The subregions into which the Palsearctic region may be divided 

 are four in number : Boreal, Steppe, Mediterranean, and Eremian. 

 The chief characteristics of these are as follows : — 



The Boreal subregion includes the whole zone of the forests of 

 Northern Europe and Asia, but some representatives of its 

 characteristic Orthopteran favina penetrate farther on north- 

 wards — into the zone of the Arctic tundi'as which has not its own 

 Orthopteran fauna. The Orthopteran fauna of the Boreal sub- 

 region is very poor, both in species and in specimens ; the 

 sviborders Mantodea and Phasmodea are entirely absent from it, 

 and of the Gryllodea we only find the Gryllus domestictis here. 

 As leading characteristics of Boreal fauna should be regarded : 

 Chrysochraon dispa7; Stenohothrus viridulus, Gomphocerus sibiricus, 

 Mecostethus grossiis, Psop/ms stridulus, and Podisma jjedestris from 

 Acridiodea, and Leptofliyes ptunctatissima^ Meconema thalassinum, 

 and Olynthoscelis griseoaptera from Locustodea. 



The great distance between, our country and the Boreal sub- 

 region causes the Boreal fauna to be of very little importance in 

 the composition of our fauna. Nevertheless, in some districts 

 of the Caucasus, as we shall see later on, the influence of the 

 Boreal fauna is rather striking : in some mountainous districts 

 we may find the typical boreal species, which are, at the same 

 time, absent from the intermediate areas between the Caucasus 

 ;and the Boreal subregion. These species with such discontinuous 

 range of distribution are of great importance to the history of 

 the fauna of the Caucasian mountains, as they give us a. hint con- 

 cerning the former contact of this fauna with that of the Boieal 

 subregion ; later on this contact was interrupted, but the cause 

 of this interruption is still unknown to us with certainty; we 

 can only suppose that this immediate connection between the 

 Orthopteran faunas of the Caucasus and of the Boreal subregion 

 took place during the Glacial period, and ceased after this period 

 had given place to a warmer and drier one, when the Boreal 

 elements of the fauna retreated to the North, leaving a few 

 relics in the high mountainous districts of the Caucasus. 



The Orthopteran fauna of the Steppe subregion is rather I'ich 

 and includes many typical forms. The most important character 

 of this fauna is the joresence of a large number of species of the 

 genus Stenohothrus. The Steppe fauna in Europe shows dis- 

 tinctly marked affinities with the Siberian, and we should suppose 

 that its representatives have migrated into Europe from Asia. 



