322 THE ENTOMOLOGIST* 



In this connection I may here remark that in all the zones in 

 the mountains (the same as in the Alps) it is singular how 

 closely the distribution of the Ehopalocera coincides with that of 

 the predominant or typical arborescent vegetation. This is 

 particularly noteworthy by reason of the fact that very few trees 

 and shrubs which constitute the facies of the different zones 

 provide the pabula of the larvae. Many low plants, on the other 

 hand, which do constitute the food of the caterpillars, possess a 

 wide distribution, or are represented in other zones by closely 

 allied species. Besides the vegetation, the climate and many 

 other factors it is evident, therefore, must be taken into con- 

 sideration in order to account for both the horizontal and vertical 

 distribution of the Ehopalocera. 



The lower hill zone rises in the Hautes Pyrenees to the height 

 of about 3000 ft. The alien but graceful locust-tree {Rohinia 

 ])seudo-acacia) flourishes in this region, growing luxuriantly by 

 the sides of the ravines and gorges in company with other 

 characteristic vegetation. 



The upper hill zone ascends above the preceding to the height 

 of about 4500 ft. The most characteristic shrub belonging to it 

 is the box, which grows in dense masses among the rocks upon 

 the rugged mountain slopes, and produces a very typical feature 

 in the landscape. 



The lower alpine zone lies between the altitudes of 4500 and 

 6500 ft., but it is exceedingly difficult in many parts of the 

 mountains to define its position with a certainty owing to the 

 absence of conifers, which constitute the typical arborescent 

 vegetation of this region in the Alps, and throughout sub-Arctic 

 Europe generally. The places of the pine and fir are thus 

 frequently occupied by the juniper and rhododendron, which, 

 owing to the scantiness of the soil, flourish abundantly in the 

 absence of the trees. It is thus often by no means an easy 

 matter to tell where this region ends and the one above begins. 



The upper alpine zone is the region of small bushes and 

 stunted shrubs, and occupies the mountain slopes between the 

 altitudes of 6500 and 8000 ft. 



The snow zone, which occupies the highest and final vertical 

 region, terminates at the point where commences the actual line 

 of congelation, which on the northern slopes of the chain lies at 

 about the altitude of 8800 ft. 



On the southern or Spanish side of the watershed bounding 

 the Hautes Pyrenees all the above vertical zones are a few 

 hundred feet higher, the altitude of the lower limit of perpetual 

 snow being about 9200 ft., this constituting a difference of some 

 400 feet. 



Allowance being made for the difference in the latitude— 

 about two degrees— between the Alps and the Pyrenees, the 

 vertical distribution of the Ehopalocera in the latter range 



