ABSTRACT.In constant light or constant darkness,Glossina morsitans morsitansWestwood were found to exhibit no obvious rhythms of parturition, but in LD 12:12 most larvae were deposited during the photophase. When a divided photoperiod chamber was used to expose the female's head to LD 12:12 and the abdomen (containing the larvaein utero) to constant light, parturition coincided with the photophase of the female's head. But, if the abdomen was exposed to LD 12:12 and the female's head received constant light or was painted with black enamel, parturition coincided with the photophase of the larva. When the female's head and abdomen both received LD 12:12 but 11 h out of phase with each other, parturition was equally frequent in each 12h fraction. The results thus suggest that both the mother and larva are capable of entraining the rhythm, and that in a normal pregnancy both participate in establishing the rhythm.
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