Field collections in Puerto Rico revealed 4 behaviorally distinct isolates ofMuscidifurax uniraptor Kogan & Legner that differed initially in diapause and nondiapause emergence, and the age when ♀ progeny were produced. Subsequent F1 and F2 progeny differed in sex ratio and total progeny production. Mating F2 ♀ ♀ from nondiapause isolates to naturally emerging ♂ ♂ from thelytokous populations significantly reduced total progeny and the proportion of ♀ ♀ toca. 20 %. These mated ♀ ♀ at first resembled in behavior those which originated from diapausing parents. Random mating within all isolates beginning in the F3, resulted in a general lower survival and progeny production but was accompanied by a rise in sex ratio toca. 50% ♀ ♀ by the F6 generation. The interinvolvement of extranuclear and genic factors is considered.