THE CANADIAN ENTOMOLOGIST. 129 



the case of Vhninia eiiphorbicz var. montivaga, an Alpine form, closely 

 resembling our var. myricce. In Dr. Staudinger's trade lists, too, most of 

 the Alpine forms are spoken of as vars. obscura, suffusa, utiicolor, etc. 



Our northern latitudes give us, generally, forms more than usually pallid, 

 and which rarely present any tendency to variation in the direction of 

 melanism. As, however, melanic tendencies were first noticed in con- 

 nection with specimens from a high altitude, it became the usual thing to 

 associate melanism with a low temperature, until the Western shores of 

 the British Isles, with a comparatively high temperature, were found to 

 produce some of our most intensely melanic forms, and it was then found 

 that melanism was accompanied by humidity rather than by a low tem- 

 perature. 



To get reliable results from actual experiment is difficult, as a certain 

 phase of melanism is frequently found to accompany degeneracy and 

 change of constitution {vide " Entomologist's Record," Vol. I., pp. 236, 

 237, 272) brought about by inbreeding. Besides, great care must be 

 taken in experiments, to see that species are chosen in which a natural 

 hereditary tendency to vary does not exist. Mr. Merrifield's experiments, 

 the results of which were read before the Entomological Society of London 

 in December last {vide "Entomologist's Record," Vol. I., pp. 267, 268), 

 appear to be open to these objections. 



It seems to me that the exciting cause to variation must act in the 

 active larval stage, and not in the comparatively quiescent pupal stage, 

 and an experiment (?) of which I have lately heard, designed to test my 

 theory of humidity, in which some pupse of Selenia illjistraria were prac- 

 tically kept in water for a week or two, whilst others were kept very dry, 

 only serves to show how hardy the pupa is, and how difficult to kill. Ex- 

 periments of this kind partake of the ridiculous and make science look 

 foolish. 



As my series of papers on this subject will take some time yet to 

 finish, I should be very thankful if any American entomologists could give 

 me information with regard to the matter, especially as to the general 

 tendency of insects to become (i) more than usually pallid in dry, open 

 areas at a high latitude, and (2) darker in humid districts at either high or 

 low altitudes. 



