1912.] 



I 



II 



III 



III 



IV 



IV 



V 



VI 



VI 



NATURAL SCIENCES OF PHILADELPHIA. 

 Table III. 



279 



Mean. 



19.527 

 18.155 

 17.360 

 16.944 

 17.717 

 17.050 

 17.789 

 18.637 

 18.116 



0.093 

 0.057 

 0.053 

 0.057 

 0.057 

 0.080 

 0.051 

 0.036 

 0.067 



Standard Devia- 

 tion. 



0.838 

 0.551 

 0.591 

 0.511 

 0.611 

 0.650 

 0.511 

 0.667 

 0.738 



0.066 

 0.041 

 0.037 

 0.041 

 0.040 

 0.057 

 0.036 

 0.025 

 0.047 



Coefficient of 

 Variability. 



4.29 

 3.03 

 3.40 

 3.01 

 3.45 

 3.81 

 2.87 

 3.58 

 4.07 



0.34 

 0.22 

 0.21 

 0.24 

 0.23 

 0.33 

 0.20 

 0.14 

 0.26 



Table IV. 



We can see (Lots I-III in Tables II, III, or b, c in Table IV) that 

 the length of the fore wings of the male butterflies diminishes grad- 

 ually as the season advances. 



That this species winters over as caterpillars was ascertained in 

 my breeding experiments, and that Lot I implies only the individuals 

 which had hibernated during their caterpillar stages is scarcely 

 doubtful, so I am inclined to attribute this difference (6) of the 

 wing-length between this lot and Lot II to some such cause 

 as mentioned by Standfuss, 2 i.e., the difference in the length of 

 the feeding period, which had happened to affect the developing 

 organisms. The same rule has probably held in Case c. In the 

 succeeding three cases, d-f, we can recognize how the length of the 

 fore wings of the butterflies, even if of the same sex and generation, 

 has the tendency to increase the more the latitude of their habitat 

 increases. 



Bachmetjew 3 has ascertained that the butterflies of this sub- 



2 Morgan, T. H., Experimental Zoology, 1907, pp. 24, 25. 

 J Experimented Entomologische Studien, II (1907). 



