Contributions to Experimental Entomology 563 



places where it was found in great numbers during the previous 

 fall ? A good parallel to this case is that of the Pyrameis atalanta 

 L., and P. cardui L., of which Standfuss says verbally in his 

 " Handbuch der palaearktischen Gross-schmetterlinge," Jena, 

 1896: "Although individuals of atalanta and cardui may be 

 observed during high summer and fall as a rule in quite as great 

 numbers and sometimes even greater numbers than the butter- 

 flies of antiopa, polychloros, c-album, io, and urticae, these two 

 species are in general very much more rarely seen in the spring 

 than the series just mentioned. Only after very mild winters 

 are atalanta and cardui found to occur frequently in spring. 

 Our severe winters evidently kill ofi^ most of the individuals of 

 these two species, which have not yet sufficiently acclimated 

 themselves to such low temperatures, and are also much more 

 rarely seen hibernating than the numerous species we have sup- 

 posed to originate in northern latitudes. Although the second 

 generation of atalanta and cardui is not exactly rare during most 

 years, this is due to the extraordinary flying powers of these species, 

 which continually push forward from milder into more inclement 

 regions." (p. 302.) 



We may, therefore, agree with the view which Scudder advances 

 in his "Butterflies of New England," that hibernation is extremely 

 rare in J. coenia throughout its northern range. It would seem 

 that, notwithstanding the much greater phylogenetic age of coenia 

 than of atalanta and cardui, it is much more difficult for the former 

 species to accommodate itself to severe cold. But if coenia is to 

 take permanent possession of the northern portions of its range, 

 and not be continually recruited in this range by specimens from 

 the south, it must acquire the ability to hibernate. It seems prob- 

 able that the imaginal insect is destined to do this, although it is 

 not impossible that the pupa may acquire the ability, for, as I 

 have stated at the beginning of my paper in connection with the 

 data received from Mr. Doll, caterpillars of all sizes are found in 

 the field till late in the fall, and this, of course, means also the pres- 

 ence of pupae. If such pupae should hibernate the butterflies aris- 

 ing from them would certainly not have the same color pattern 

 as those whose whole development occurs during the warm sea- 



