March, 1902.] SeIKERT : NORTH AMERICAN ARCTI1D.E. 9 



The broods derived from females exposed May 14th have been 

 reared under normal conditions ; the individuals of each of the other 

 two were partly submitted to high or low temperature. 



A temperature of + 40° C. for 100 hours or + 4° C. for 30 to 

 40 days had the peculiar effect on newly formed pupae of 7iais to pro- 

 duce asymmetrical results in regard to primaries and secondaries irre- 

 spective of sex, but more pronounced with females. Heat as well as 

 cold caused a tendency to expand the longitudinal and mostly always 

 present but rudimentary transverse posterior stripes on primaries often 

 to such an extent as to leave only two limited streaks of black color 

 above and below median band, never impairing though the black costal 

 margin or spreading practically beyond transverse posterior stripe. 



Heat affects the secondaries of the males by a reduction of the black 

 maculation, whilst the pale ochre color turns lighter but brighter. 

 The discal spot weak but mostly as in the normal forms present. With 

 the females heat reduces the black marginal band or maculation per- 

 ceptibly and intensifies the color, animating the vital activity even so 

 far as to produce ultimately true melanotic forms. 



Exposure to low temperature, with both sexes, enlarges the black 

 maculation or marginal band decidedly, often even with the males 

 uniting the black spots to an irregular band, the black color losing 

 though much of its dee|)ness. 



The red or yellow color of the hind wings is not dependent on 

 thermal conditions and the inclination to melanism seems to be con- 

 fined to the female forms with yellow hind wings. 



The larvae of A. nais and related species are often infested by 

 a dipterous parasite, Thelaira leucozotia Panz., which fastens its eggs 

 mostly on the head of the larva. Wintering larvae not carefully at- 

 tended to are subject to muscardine to an alarming extent. 



EXPLANATION OF PLATE IL 

 Arctia nais, male ; found in copula with exposed f , June 8. 

 " " " imago, June. 



"■ " July. 



July. 

 " " female ; " July. 



" " " " May. 



" " " . " December; xeartA on Cicho?iu»i endiTia. 



" " male; pupa on ice, July 10 to Augu.st 10 ; imago, Aug. 19 



Fig. II. " " " " " July 20 to August 20 ; " " 30 



