• VARIATION IN EUROPEAN LEPIDOPTERA. 8 1 



of this dark form of Tephrosia crepuscularia \ Another year he bred 

 250 images from ova of this variety, but twenty of them reverted to 

 the pale type. We have here the history of a recurrent aberration 

 becoming established as a true variety ; which might, in process of 

 time, in favouring circumstances, become a species. The melanic 

 forms of Aifiphidasis betularia and Xylophasia Polyodon are, I think, 

 inconstant ; but a very interesting and beautiful case of local dimor- 

 phism occurs at Digne, in the Basses Alpes, where the abnormal form 

 Ho7inoratii is occasionally procurable by rearing a large number of 

 the larvae of Thais Rumina. As this dimorphic form is merely 

 produced by extreme effusion of the normal crimson colouring, it is 

 likely enough to occur elsewhere. A most remarkable aberration has 

 been produced latterly in what I may call our now domesticated 

 insect Liparis dispar, an account of which has, I believe, appeared 

 in one of our Natural History magazines. It is almost unique in 

 affecting the contour of the wing, and not the colour and pattern. 

 In rearing a brood of L. dispar it has been found that a considerable 

 number of the images emerge with a curious deformity in the hind 

 wing, and sometimes the fore wdng also. This consists of the loss of 

 a semicircular portion from the outer margin, forming a gap in the 

 continuity. When this affects only a single wing, or occurs irregularly 

 on more than one, it appears a mere monstrosity ; but specimens 

 also occur which have corresponding gaps in both hind wings. Now 

 if by interbreeding their disposition became regular, uniform, and 

 hereditary, we might have a very distinct species formed within the 

 lapse of a few years. The contour of the wings is so rarely modified 

 by variation, at least in temperate climates, that such a case as this 

 possesses more than ordinary interest. 



There is another class of dimorphism which has been termed 

 seasonal dimorphism, and an extreme illustration of it is to be found 

 in the case of Vanessa Levana, and its summer representative, 

 V. Proi'sa, which differs so greatly from the spring insect as to have 

 been formerly classed as a distinct species. And if the pupse of 

 V. Prorsa be subjected to a very low temperature, we are surprised by 

 the appearance of a third and intermediate form, ab. Porima. This 

 phenomenon in some cases may have given rise to varieties. For 

 instance, the familiar Bombyx quercus^ in countries where it is obliged 

 to hibernate in the larval condition in consequence of short summer 

 seasons, appears as B. callunce. Ephyra punctaria^ Sele7iia illunaria, 

 S. Iu7iaria, and others exhibit, more or less, this seasonal dimorphism. 



I shall not detain you with many observations on the occurrence 

 of monstrosities, deformities, and hermaphroditism, as scarcely 

 coming w ithin the scope of my paper. Hybrids seem to be irregular 



Nov. 1884. 



