132 YORKSHIRE NATURALISTS' UNION. 



males of northern species being more in need of heat-absorbent 

 colouring than the females for the reason indicated in the case 

 of Acidalia mbricata, might be expected more completely or 

 more quickly to assume it, and that conservatism which 

 Edwards and Weismann have attributed to the female sex, would 

 be at least partially accounted for. 



I believe it to be a fact that the females of the Shetland 

 Lepidoptera are in some degree less differentiated from the 

 typical forms than the opposite sex, although the distinction is 

 not strongly marked. Mons. Girard found by experiment an 

 excess of natural warmth in males over that of females. * 



It might also be expected that whereas the arguments 

 which I have used can obviously apply to the perfect insects 

 only, the larvce would show no tendency to vary in the direction 

 of melanism, I am informed by Mr. Meek, to whose spirit of 

 enterprise we are chiefly indebted for these interesting additions 

 to our cabinets, that he has not noticed that the larvae of Lepi- 

 doptera differ in color from north to south; he has had many 

 opportunities of observing this point, having collected for many 

 years in all parts of the country, and his opinion is that they do 

 not. 



Black varieties of larvse are not unknown; a black form of 

 Abraxas grossulariata occurs in the neighbourhood of New- 

 castle, but the perfect insects produced from these larvse are of 

 the ordinary type and by no means raelanic. The day feeding 

 larvge of the genus Melitsea are almost uniformly black, but not 

 more so in the north than in the south, and these feeding for 

 the most part upon different species of Plantago, have the ad- 

 vantage of strong protective resemblance to the black undevel- 

 oped flower-heads. Yet no genus of butterflies exhibits more 



* ' Etudes sur la chaleur libre des invertebres ' — Annales des Sciences 

 Naturelles, 5th ser., vol. xi, p. 201. 



Trans. Y.N.U., 18S3 (pub. 1SS5). Series D 



