2S2 THE CAUSES WHICH 



As we ascend the liills and mountains of Europe butterflies 

 and moths become small and dark; and their sexes often lose 

 their colour differentiation, or become discriminated anew by 

 melanism. Mr. Goss, at a meeting of the Entomological Society, 

 exhibited a series of specimens of our somewhat local blue 

 butterfly I* oly ommatiis Arion, taken during June, 1877, among 

 the Cotswold Hills. One-third of these were far below the 

 average dimensions, whereas those specimens he had previously 

 obtained from their Devonshire and Northamptonshire habitats. 

 Bolt Head and Barnwell Wold, I think we may presume, were, 

 as a rule, of the normal size. I have myself taken the male 

 of the Orange Tip Butterfly on Robin^s Hill, near Gloucester, 

 only 1" in alar expanse, and the Fritillary Melitoia Athalia on 

 Alpine heights dwindles to less. In a few cases it is the female 

 of Alpine butterflies alone that is melanic."^ A large number of 

 these Alpine butterflies are likewise normally dark. Nearctic 

 species present the same features on the heights. Limenilis 

 Misipjms on the Catskill Mountains of North Amei'ica loses dark 

 markings, and L. Arthemis has an Alpine form, for example. 



Arctic Lepidoptera are equally variable with Alpine, and this it 

 is considered in either case may be owing to an enforced lengthen- 

 ing of the period of their transformations beneath the snow, and 

 to their isolation or segregation. At Grinnell Land, between the 

 parallels of 78*^ and 83*^ north latitude, one month each year is the 

 longest period insects can appear in the perfect state, and six 

 weeks is the period in which phytophagous larvae can feed ; so 

 that the pupal state must here be generally of long duration. 

 In Newfoundland we find the variety frigida of the common 

 American Pieris oleracea differs from its Canadian iy^e in being 

 more marked with black along the veins, both at the base and tip 

 of the wings. Pajnlio Tnrnus is dwarfed, palei*, and with 

 narrower black borders. The caudal lobe or tail of the hind mng 

 in Fa];)iUo hrevicauda, Saund., a local form of Asierim, is reduced 

 by one-half. 



Woody coverts and proximity to the sea, as also the smoke of 

 towns and manufacturing districts, are associated with variety and 



* Pieris Napi, var. Byonice ; Toli/oinmatits virgaurcce, var. Zermattensis ; 

 Arffi/nnis Paphia, var. Valezina. This may be due to the greater duration of this 

 sex in the jiupal state. 



