AN TNTERNAT. PARASITE OF THYSANOPTERA. 



35 



RELATION AND PROPORTION OK SEXES. 



During the course of this investigation hundreds of specimens of 

 this insect have been reared, but among this number it has been 

 impossible to find a single male. Furthermore, up to October 1, 

 1911, a generation of females had been reared from a female and 

 these in turn had oviposited in their host. Regarding the length 

 of time this insect might continue to multiply without the intro- 

 duction of the male, or what proportion of males might be produced, 

 it is impossible to determine at the i)resent writing. 



PARTHENOGENESIS. 



This insect reproduces parthenogenetically to a large extent, for, 

 as the accompanying table indicates, in every one of a number of 



Fig. 7. — Thripocfcnus russcUi: Adult. Greatly enlarged. (Original.) 



experiments performed to determine this point, the fact was clearly 

 proven by the development of the parasite in thrips larvre oviposited 

 in by unfertihzed females. 



Table I. — Results of oviposition hij unfertilized feinales of Thripoctenus russclli. 



