The sex ratio and oogenesis of Pseudococcus eitri. 7 
7 
were laid by each female during a period of about three weeks. After 
the first individuals of each brood had reached the stage where sex 
could be distinguished, the total number of larvae was established as 
closely as possible. Then, at intervals of a few days, the males that 
could be recognized as such, were counted and removed. This gave 
the total number of males in the brood when all its members had 
reached maturity, while corresponding counts established the number of 
larvae lost in the course of the experiment. Despite every precaution, 
such losses could not be eliminated entirely. 
Date of isolation No. No. | Loss approx. 
of Mother of Females of Males R 
mee" ate Alia LL Saas 
hihy Ts al) See 9 4 40 
Merona 1920) oe 21 | 19 30 
November 20, 1921 = . - . . 17 21 15 
January 9, 1922 ...... 2 1 0 
January 9, 19222 ...... 27 | 36 15 
Bunuarvio 1992... .. „nn. 66 | 44 | 15 
Total | 142 | 125 
It will be seen that the sex ratio indicated by the total count 
is by no means an abnormal one, and if encountered in random counts 
of that size, would hardly give rise to the suspicion that parthenogenesis 
may occur. How then is this difference between random counts and 
counts made on broods under control to be explained? 
Primarily the reason for this variation in the two counts lies in 
the difference of the duration of life between adults of the two sexes. 
The mature female, as was discovered in the course of the various 
breeding experiments, live for a period of three months or more; in the 
adult males on the other hand, the period of life is a question of days. 
Thus four mature males, kept under observation, lived from three to 
six days. A second reason is to be found in the fact that except in 
the last two instars, the males closely resemble the females in appearance 
and in random counts many of them are no doubt counted as females. 
Even in the last two instars, the diminutive size of the male and its 
habit of hiding in various corners and interstices of the host plant, 
must often enable it to escape notice. This is especially true in Pseudo- 
coccus citri, where the pupal male often neglects to spin the wooly 
