June, '11] 



SEVERINS ON WALKING-STICK 



309 



in groups, the grouping being made according to sex and the number 

 of molts. 



TABLE n 



STAGES IN MOLTING IN D.\TS OP DIAPHEROUEKA FEMORATA REARED IN JUNE, JULY AND AUGUST. 



Date of hatching 



1909 6/9 . . 

 1909 6/9 . . 

 1909 6/11.. 

 1909 6/12.. 

 1909 7/22.. 



Averages. 



1909 6/9 . . 

 1909 6/9 .. 

 1909 6/12. . 

 1909 6/12. . 

 1909 6/13.. 



Averages. 



1907 6/13.. 



1907 6/22.. 



1908 7/6 . . 

 1908 7/9 . . 

 1908 7/13.. 



Averages. 



1908 6/23. . 



1908 6/24.. 

 1908 6/30.. 

 1908 7/17.. 

 1908 7/22.. 



Averages. 



907 6/13 9 



12.6 



15 

 15 

 13 

 13 

 13 



13.8 



11.6 



7.6 



9.4 



7 

 9 

 9 



8 



7 



8.4 



9.6 



9 

 9 



7 

 9 



7 



8.2 

 9 



10.4 



9.2 



11.4 

 9 



ll 

 II 



40.6 



38 

 44 

 40 

 44 

 41 



41.4 



43 

 45 

 45 

 53 

 48 



46.8 



46 

 53 

 51 

 47 

 50 



49.4 



7/19 

 7/21 

 7/19 

 7/22 

 9/3 



7/17 

 7/23 



7/22 

 7/26 

 7/24 



7/26 



8/6 



8/20 



8/31 



8/30 



8/16 

 8/20 

 8/31 

 9/10 



8/5 



From this table, it is evident that there is a wide variability in 

 the interval between the different molts in the same walking-stick 

 and also a considerable amount of variation in the time of correspond- 

 ing periods in different specimens. The period between molts varies, 

 under normal conditions, from six to fifteen days, the first and last 

 stadia being usually somewhat more prolonged than the intermediary 

 ones. And yet Trouvelot (99) writes, that in the case of Diapheromera 

 femorata "he had observed many specimens and the interval of molt- 

 ing was always seventeen days." What wonderfully regulated speci- 

 mens he must have observed! 



The following table shows the average measurements of various 

 parts of the body of ten walking-sticks after the first and second 

 molts and of five or ten male and female specimens after the third, 

 fourth and fifth molts: 



