Carl E. Venard

MEASUREMENT OF SALIVATION BY AEDES AEGYPTI (L.) FEEDING ON A LIVING HOST.

Abstract Aedes aegypti mosquitoes having tritiated water in their body fluids were permitted to feed on living suckling mice. The quantity of saliva a mosquito left in a mouse was computed as the ratio of the radioactivity of the tritium found in the mouse and of the specific activity of the mosquito fluids. The fluids were extracted from individual mice and individual mosquitoes by lyophilization, and they were assayed for tritium in a liquid scintillation spectrometer. The quantity of saliva left in a mouse when a mosquito took a blood meal had a range of 1–13 μg, with a mean of 4·7 μg.

Larval diapause in the mosquito Aedes triseriatus: Effects of diet and temperature on photoperiodic induction

Abstract Larval diapause was induced in both a northern (Ohio) and a southern (Alabama) strain of Aedes triseriatus by photoperiodic treatment of the larval stage itself. The effect of a short-day (10 hr) photoperiod during larval development was cumulative and resulted in failure of the fourth instar to pupate. The larvae, which had been obtained from long-day (16 hr) eggs, underwent diapause when their development was slowed by a low-quantity diet or low temperature (16°C) for a sufficient number of days to allow the short-day photoperiod to exert a visible effect.

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

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.