The Effects of atmospheric Pressure on the Flight Responses of Aëdes aegypti (L.)

Abstract

Laboratory investigations with the mosquito AËdes aegypti (L.) have shown that air pressure has the following effects on flight activity:The effects of pressure changes are consistently large enough to constitute an important factor in determining activity provided the mosquitos are acclimatised first to a particular pressure level.The period of constant conditions necessary for complete acclimatisation was between three and six hours for all pressure conditions investigated.When the period of acclimatisation had been fulfilled, the flight activity was approximately the same at all levels of static pressure investigated between 550 mm. and 800 mm. Hg.After complete acclimatisation the activity following a moderate decrease in pressure was 1·5 to 2·4 times that following a similar increase in pressure when the general pressure level exceeded 735 mm. Hg.When the general pressure level was less than 735 mm. Hg., the activity following a decrease in pressure was less than that following an increase; it would appear that 735 mm. is a critical pressure level for the stock of A. aegypti employed.The activity during a uniform rise in pressure from 530 mm. to 730 mm. at 7·7 mm. /min. was at least 10 times that during a reverse fall in pressure fall in pressure at the same uniform rate.Provided the rate of change was not greater than 1 mm./sec., the maximum flight activity for falling pressures was observed at 780 mm. while the maximumfor rising pressures was observed at 735 mm.