164 



The Naturalist. 



usually imposes in order to keep species within moderate limits. If 

 this argument be accepted, it goes far to solve the problem ; but I 

 think, if we carefully examine facts, that this reasoning will not 

 satisfy. 



I shall bring forward facts illustrative of the subject, and these 

 illustrations will be taken chiefly, though not entirely, from the order 

 Lepidoptera ; and this for two reasons — first, because it seems to be 

 the favourite order with entomologists, and secondly, because it 

 appears to me to afford on the whole the best evidence on the question. 



An instance of excessive abundance is r^^corded in the Zoologist for 

 1848, page 2331, by W. Turner, M.A., of Uppingham. I give a 

 condensed account in his own words. '• During an entomological 

 ramble last June, my attention was arrested by the leafless and lifeless 

 appearance of a venerable oak which, in spring, I had observed 

 covered with luxuriant foliage. It stood alone, and was not within 



fifty yards of any other tree I v/ent to examine it, and found 



the trunk completely covered with a fine transparent web, and on 



closer inspection observed the crevices in the bark filled (I 



might say) with small pupse I carried ofi" vast numbers of 



these, but to my surprise they all turned out to be examples of Tortrix 

 mridana. I say surprise, because I never found these pupse otherwise 

 than rolled up in a living oak leaf. Here, then, is the interesting 



part — leaves were wanted for food they must therefore make 



the most of their present supply, and it became necessary to eat what, 

 under other circumstances, would have formed a protection for the 

 pupse." He goes on to say that " there was not a vestige of leaf left 

 on the tree.'' Mr. Turner does not assume that all the foliage was 

 destroyed by this species alone, but I have quoted sufficient to show 

 the excessive abundance of Tortrix viridana in this instance. It is to 

 be remarked of this species, as well as of some others, that when they 

 appear in excessive numbers, such excess is not usually general, or 

 spread over a large extent of country ; it is frequently very local, and 

 I submit to you whether this fact does not increase the difficulty of 

 our being able to account for such occurrences, and whether it would 

 not materially assist us in the inquiry, if we could ascertain, when such 

 cases occur, to w^hat extent they prevail, and under what atmospheric 

 or other conditions : of course it would require a combination of 

 observers. 



I pass on to a case which has occurred recently, and within this 

 district. In the month of June last year, a great outcry came from 

 Clitheroe. An army of the larvae of Charcsas gramink, or the antler 



