320 THE ENTOMOLOGIST. 



ON THE VEETICAL DISTRIBUTION AND DERIVATION 

 OF THE RHOPALOCERA IN THE PYRENEES. 



By W. Harcourt-Bath. 



. On the occasion of a recent entomological expedition to the 

 Central Pyrenees, part of my programme consisted in defining 

 the vertical zones of vegetation, to provide a basis for studying 

 the vertical distribution of the Rhopalocera in the region under 

 consideration. The results arrived at, together with certain 

 other facts and conclusions obtained during the course of the 

 investigation bearing directly upon the subject of vertical or 

 climatal distribution, I propose to present to the readers of the 

 'Entomologist' in the present paper. 



The district investigated consists of that portion of the 

 chain situated within the French Department of the Hautes 

 Pyrenees, and may perhaps be regarded as representing the 

 average climatal conditions of the whole range. On account of 

 its central situation the precipitation is less than that further 

 to the west, and greater than that which occurs in the continua- 

 tion of the chain in the direction of the Mediterranean, which 

 latter portion possesses a very dry climate indeed. The flora of 

 this region is in character similar to that occurring on the 

 northern slopes of the Alps, and in Cold Temperate Europe 

 generally. 



The olive zone (or, as it ought more properly to be called in 

 this district, the pseudo-olive zone) is theoretically represented 

 (from a climatological point of view) in the Department of the 

 Hautes Pyrenees at the lower elevations, where the mean annual 

 temperature rises in some situations as high as 59° Fahrenheit, 

 but practically (from a phyto-geographical standpoint) this is 

 not the case, for, as I have already stated, the vegetation is 

 wholly that of Northern Europe. The olive and other character- 

 istic trees and plants of the warm temperate zone just commence 

 to occur in one direction about ten or a dozen miles to the east 

 of the Department in the vicinity of Bagneres de Luchon, and 

 in another as soon as we cross the southern watershed and 

 descend into Spain. Theoretically this zone terminates here at 

 about the altitude of 1000 ft., but of course there is no phyto- 

 geographical line of demarcation between it and the one above, 

 so that if we are to admit it at all it can only be estimated by 

 means of a calculation. 



The vine zone rises above the preceding to the height of 

 about 1800 ft., which altitude is also considerably below the 

 theoretical elevation it should be, based upon the mean annual 

 temperature alone. It is, however, consistent with the con- 

 ditions which exist in the zone below. 



