82 



VARIATION IN EUROPEAN LEPIDOPTERA, 



attempts to accomplish 'per saltum,' and in a single generation, what 

 the laws of nature prescribe to be effected only step by step ; that is, 

 the inauguration of a new species. The penalty for such an infrac- 

 tion of her law is extinction, and accordingly hybrids are infertile. 

 Boisduval has remarked that though many of the ZygcenidcE belonging 

 to closely allied species frequently couple unnaturally, yet that he 

 has invariably found the results of such unions are infertile, although 

 the ova of this genus are very easy to hatch ; and this is the more 

 remarkable considering how many of these species are linked by 

 almost imperceptible gradations to each other. 



Deformities in the imago seem to be usually the result of some 

 injury suffered in a previous condition of existence. Experiments 

 have been made by a Belgian entomologist by which it was found 

 that when a leg of the larva was cut off, the corresponding member 

 of the imago was wanting on emergence. 



Hermaphroditism assumes two forms, and it would be interesting 

 to have a list collected of the species in which this remarkable 

 imperfection has shown itself. One form is that in which opposite 

 sides of the insect are of opposite sexes, and this gives rise to a very 

 monstrous appearance, especially when the sexes differ in size and 

 colour of wing, and in the pectination or filiform shape of the antennae. 

 The other form of hermapliroditism is when the sexual characters are 

 intermingled so that both sides partake equally of the diverse sexual 

 characters. The pretty A7ithocharis EtLphenoides is very subject to this 

 latter form. 



And now, in closing my subject, I will refer to a few matters worthy 

 of attention, but which I have no time to discuss — namely, the general 

 influences of localities. Mr. Wollaston has stated that the proximity 

 of the sea influences the coloration of insects. The chalk formation 

 undoubtedly produces in some insects a very pale and blanched colora- 

 tion, and such aberrations I am inclined to regard as the effect of 

 mimicry in the adoption of a protective colouring. Some, again, hold 

 that soils strongly impregnated with minerals affect the local fauna ; 

 but all naturalists are agreed that the strongest developed variations are 

 to be found generally in places whose creatures are cut off from 

 intercommunication with the rest of their kind by rr^ountains, vast 

 forests, the sea, or other natural barrier. Isolation no doubt begets 

 peculiarity, and in the remarkable series of Shetland insects taken by 

 Mr. McArthur w^e have interesting evidence of the fact. 



I shall now sum up shortly the points I have brought before you. 

 Of the past history of species we can only reason from analogy ; but 

 on comparison of the species grouped together in one genus, the 

 student of classification cannot but be struck with many common 



Naturalist, 



