THE CANADIAN ENTOMOLOGIST, 203 



cool weather a very few venialis also — these in late September and in 

 October until severe night frosts occur. In autumn the grades of earlier 

 dates are nearer the type ; those appearing later progressively approach 

 venialis. 



I would suggest that the term " dimorphic variety " hardly applies 

 properly to venialis. The variation is multiform, and the intergrade 

 examples largely outnumber the instances of the extreme ^'- vei-nalis'' type 

 as described and figured. Venialis is not a variety abruptly contrasting 

 Avith a type form, but merely the extreme term of a series of variations 

 departing from type. 



Vol. I of Mr. Edwards' " Butterflies of N. A." contains plate with 

 accurate and beautiful figures of venialis. 



AN ACCOUNT OF SOME FARTHER EXPERIMENTS UPON 



THE EFFECT OF COLD IN CHANGING THE FORM 



OF CERTAIN BUTTERFLIES. 



BY W. H. EDWARDS, COALBURGH, AV, VA. 



In May, of the present year, at Coalburgh, I bred a large number 

 of larvae from eggs laid by thajvs. var. marcia ; also several from eggs 

 laid by ajax, var. Walshii ; and from eggs laid by Lye. pseiidargiohis ; 

 and all of the chrysalids of tharos, and part of those of the other two 

 species, were placed in small tin boxes as they formed, and at different 

 intervals thereafter, lo, 20, 60 minutes up to some hours, and one and two 

 days, were laid in the ice box on top of the ice. The box was supplied 

 with ice once a day. I intended removing the chrysalids at irregular 

 periods, so as to see what length of exposure to cold would suffice to 

 change the form of the butterfly, and hoped also to ascertain how soon 

 after the forming of the chrysalis the cold must be applied to produce the 

 desired effect. But the tharos chrysalids had scarcely begun to form when 

 I was called to New York, and had to leave charge of them and the larvse 

 to a member of my family, who followed my directions faithfully as to 



