The effects of photoperiod and temperature on the induction of diapause in Aedes triseriatus (Say)

Abstract

The Aedes triseriatus eggs used in these experiments were from two colonies maintained in laboratory culture under identical conditions for numerous generations. One colony was established with larvae collected in Hocking County, Ohio, and the other colony was established with larvae collected in Montgomery, Alabama. The Ohio strain diapaused only as eggs whereas the Alabama strain diapaused either as eggs or as fourth instar larvae. Experiments were designed to investigate the influence of several factors on the induction of diapause in eggs. Specifically these were: the effects of several day lengths on eggs, the effects of temperature on eggs, the effect of day length on the parents of the eggs, and combinations of these factors. The direct photoperiodic treatment of the eggs produced the most marked effect; the photoperiodic treatment of adults showed no effect on induction of diapause in their eggs. Eggs maintained at 18°C had higher induction scores than eggs maintained at 27°C. The photoperiod threshold for Ohio strain eggs was between 13 and 14 hr and that for the Alabama strain was between 12 and 13 hr, thus reflecting geographical differences in latitude between the two strains. The interaction of temperature and photoperiod was studied for Ohio strain eggs by using a wide range of temperature treatments while keeping the photoperiod treatments near the critical length. Both temperature and photoperiod caused differences in diapause induction and there was a significant interaction between these factors.