LENGTH OF DEVELOPMENTAL PERIOD 23 



Fourth stvcep- J 76 adults = |^^ ^ 



Total of catch 177= jioi nymphs = j^^ ^ 



Siuiimarij for the four siveeps. 



Adults— 123 (? + 40 $ = 163 ... Percentage, Males 75"4 



,, Females 24"6 

 Nymphs— 38 c? + 107 ? = 145 .. Percentage, Males 26"2 



Females 74' 8 



The nymphs belonged, in the great majority of cases, 

 to the last instar. A few were in the second to the last 

 instar but no specimens belonging to earlier stages were 

 found. 



The above figures furnish a fairly accurate picture of 

 the state of development at the beginning of October. In 

 November, practically no immature specimens were to be 

 found in the field. 



In summing up the results of experiment and obser- 

 vations, we find that the males require from two to three 

 months for their development while the females need two 

 and a-half to three and a-half months, or approximately 

 half a month longer. 



Still another feature which has not been noted in the 

 description of the instars is the development of the 

 posterior part of the abdomen and the external sexual 

 organs. While the general appearance of male and female 

 nymphs is practically the same up to the fifth instar, when, 

 as described, the males suddenly show a higher develop- 

 ment of the wing-buds, the sexes can be distinguished 

 from the day of hatching by means of an examination of 

 the posterior end of the abdomen. 



Plate IV, Figs. 1-21 show in outline the gradual 

 stages in the development of the posterior end of the body. 

 Figs. 1-11 show the various stages in the female, while 

 Figs. 12-21 show the same stages in the male. 



An examination of the figures illustrating the devel- 

 opment of the ovipositors shows that the upper pair 

 arises as a pair of outgrowths from the ventral region of 

 the ninth abdominal segment, while the lower pair arises 

 similarly from the eighth abdominal segment. In the first 

 instar, the upper pair have the shape of two approximately 

 equilateral triangles with their bases touching and attached 



