THE YOUNG NATURALIST. 



141 



groups of beetles, elsewhere excessively numerous, which absolutely require 

 the use of their wings, are here almost entirely absent." His conclusions are 

 as follows : " These several considerations make me believe that the wingless 

 condition of so many Madeira beetles is mainly owing to the action of 

 Natural Selection, combined probably with disuse. For, during many suc- 

 cessive generations, each individual which flew least, either from its wings 

 having been ever so little less perfectly developed, or from indolent habit, 

 will have had the best chance of surviving from not being blown out to sea ; 

 and, on the other hand, those beetles which most readily took to flight would 

 oftenest have been blown to sea and thus destroyed." 



If then this much be admitted, that the rudimentary wings of those insects 

 that have them in this state, is owing to disuse; in order to find the cause, 

 we must endeavour to show that it was for the advantage of the species that 

 it should not fly. My suggestion already referred to I may quote here : " The 

 season at which these species emerge is the stormiest of the year. The trees 

 are stripped of their leaves, and the shelter afforded by woods and hedges, 

 from severe winds, is less at this period than at any other. Insects flitting 

 about from tree to tree would be more liable to destruction, and it may, 

 therefore, be that partly from the fact that those who could not fly were 

 more likely to escape during the prevalence of a storm, their wings may 

 gradually have become aborted as we find them." Mr. Anderson's suggestion 

 is that those with undeveloped wings would be better able to conceal them- 

 selves from birds, and, of course, when the trees and hedges are stripped of 

 their leaves there is really less opportunity for concealment, expecially for 

 Lepidoptera whose wings do not fold up. Mr. Pearson then adds a third sug- 

 gestion, and a very important one, that those females that had not expended 

 their vital force on the developement of their wings, would " propagate a 

 greater number of offspring," with the inherited tendency of undeveloped 

 wings. It seems likely then that all these suggestions help us to the solution 

 of the problem so far as it relates to these genera. What cause has 

 operated to produce the same effect in other genera has yet to be sought, 

 and, I hope, the subject so ably introduced by the members of the Hagger- 

 ston Society will not yet be allowed to drop. 



REVIEW. 

 THE LEPIDOPTERA OE DORSETSHIRE. 



By C. W. DALE. 



This volume is another valuable contribution to Entomological literature, 

 in the shape of one of those County catalogues, that are alike interesting to 



