i6o 



THE BRITISH NATURALIST. 



[JU1Y 



THE SEXUAL DISTINCTION OF INSECTS. 



BY C. W. DALE, F.'E.S. 



In a great number of species the differences between the sexes are 

 so slight as to be hardly discernible, except on an examination of 

 the abdomen ; still, in a large number there is a most remarkable 

 difference, whether in form, size, or colour. 



L— Disparity of Colour. 



The sexes of Butterflies, though generally resembling each other, 

 occasionally offer various distinctions, the males in such cases being 

 almost invariably the most gaily coloured. This is especially the case 

 with the Purple Emperor, the Blues, and the Coppers. In these, the 

 upper side alone offers this distinction ; the Orange-tip, however, has 

 the tips of the fore-wings coloured orange on the under side as well as on 

 the upper. On the other hand, in the Purple Hairstreak, the individuals 

 which have a bright purple patch on the upper surface of the wings— 

 and are the most beautiful — are the females ; as is also the case with 

 the Brown Hairstreak, except that in this species the patch is of a dull 

 orange. The female of the Brimstone is of a much whiter yellow than 

 her consort. The female of the Clouded Yellow differs from the male 

 by having spots in the margin ; it has, moreover, a variety called Helice, 

 which is of a dull greenish yellow. Argynnis Paphia has also two 

 forms of the female, one which closely resembles the male, a second of 

 a dark greenish brown called Valezina. I will now enumerate the 

 British species of butterflies the sexes of which can be distinguished 

 from each other by colour differences : — 



G. Rhamni, male bright, female whitish brimstone. 



C. Edusa, female by spots in the margin. 



C. Cardamines, males by an orange blotch. 



L. Sinapis, male by having blacker* tips to the fore-wings. 



P. Brassicse, rapse, and napi, by female having black spots on the 



fore -wings. 

 T. Betulae, female by a dull orange patch. 

 T. Pruni, female has a tawny fascia. 



T. W. album, male has an ovate glabrous spot on fore-wings. 

 T. Rubi, male has an ovate white or black spot on fore-wings. 

 T. Quercus, female by a purple patch. 



C. Dispar, male bright copper, female darker and more spotted. 



P. Argiolus, female by a black border to the fore-wings, which is of a 



deeper width in the summer than in the spring brood. 

 P. Arion, female by having the black spots on the fore-wings of a 



larger size than the male. 



