June, '11] SEVERINS ON WALKI.VG-STICK 315 



stick devoured the remaining portion of the metathorax and abdomen. The appetite 

 of the creature was still not satisfied, for it went carefully over the leaf, vibrating 

 the palps continually in search of more of its integument. Finally the walking-stick 

 discovered the front leg, which was still adhering to the leaf and devoured it. Again 

 it began to search actively for more of its former exoskeleton. We then took another 

 molted skin of a different walking-stick and offered it to the greedy creature, and the 

 Phasmid began to devour this skin also. It ate, however, only the head and front 

 leg, when it was disturbed at its meal by another walking-stick coming in contact 

 with it. Apparently the instinct of the walking-stick does not carry it far enough to 

 recognize its own molted skin. 



Godelmann (33) in his work with Bacillus rossii writes, "Nach 

 der letzten Haiitung, die bei rneinen Zuchten etwa in December 

 erfolgte, beginnt das Thier sofort Eier zu legen." Meissner (55), 

 however, found that with Dixippus morosus, "Etwa 8-10 Tage nach 

 der VI Hautung beginnen die Imagines Eier abzulegen und setzen 

 dies nun standig fort." With Diapheromere femorata, we also found 

 that the females do not begin egg-laying immediately after the last 

 molt, but that there is an interval of 6 to 10 days between the last 

 molt and the laying of the first egg. These intervals in three speci- 

 mens, which had been reared under as nearly normal conditions as 

 possible and which had molted four times, were 7, 9, and 10 days, or 

 on an average 8.66 days; the intervals in twelve walking-sticks 

 which had molted five times, were 6, 6, 7, 8, 8, 8, 8, 8, 9, 10, 10 and 10 

 days, or on an average 8.16 days. From the averages it is apparent 

 that no very great difference exists in the interval between the last 

 molt and the laying of the first egg in the walking-sticks which molt 

 four or five times. 



Specimens of Diapheromera, which molted four times, reached 

 sexual maturity, on an average, in 50.06 days, while individuals 

 which molted five times required 57.56 days on an average, or an 

 extra 6.6 days before beginning the egg-laying period. It is evident 

 thus, that those walking-sticks which molted four times, omit the 

 fifth molt and yet reach sexual maturity nearly a week earlier than 

 those specimens that pass through five molts. In all probability, 

 temperature plays an important role in the rate of development, 

 but temperature alone does not explain why some walking-sticks 

 molt four times and others five times. We have repeatedly reared 

 a number of Diapheromera which were hatched on the same day, fed 

 with the same kind of food and kept in the same breeding cage 

 throughout their entire life history under exactly the same condi- 

 tions of temperature, and yet some specimens molted four times 

 while others molted five times. Further experiments are necessary 

 to determine a solution of this problem. 



The eggs, after passing out of the vaginal orifice, may be retained 



