36 Trans. Acad. Sci. of St. Louis. 



short copulating period with perfect opposition, a long- 

 copulating period with imperfect oviposition, and vice 

 versa. 



(d) The relation of the difference in the ages of the par- 

 ents at the time of copulation to the number of eggs 

 retained at death. 



The figures show that there is a direct relation between 

 the ages of the parents at the time of copulation and the 

 number of eggs retained at death. In A 15 we have the 

 most perfect oviposition, there being only a difference 

 of 20 minutes in the ages of the male and female. In A 

 10, A 9, and A 10 a , we have perfect or almost perfect 

 oviposition. In each of these cases it is shown that the 

 female was more than two days younger than the male 

 at the time of impregnation. In A 8, A 12, and A 14, we 

 have very imperfect oviposition, the number of eggs re- 

 tained at death being 98, 55, and 125 respectively. In each 

 case we find the female older than the male. 



The fact that there is a relation between perfect ovi- 

 position and the younger age of the female, and between 

 imperfect oviposition and the older age of the female 

 can be accounted for in this way. Each individual is des- 

 tined to live for a certain length of time, females from 

 6 to almost 10 days. Where the male is of equal age or 

 older than the female we have perfect or almost perfect 

 oviposition. To insure the deposition of all the eggs, the 

 male, so to speak, must be in readiness, waiting for the 

 female to hatch. In the cases where no males were at 

 hand when the females had hatched and the females were 

 compelled to await impregnation for a certain number of 

 their days, which were spent in activity with consequent 



