The effect of temperature on the growth rate and survival of the immature stages of Aëdes aegypti (L.) was studied by rearing them at each of a series of constant temperatures from 14–38°C. in water to which adequate food (bakers' yeast) was added. Larvae were hatched, by immersing eggs in water, in four successive groups with an interval of six hours between each, and six hours after the last group hatched, and every 24 hours thereafter, those surviving in each group were recorded and transferred to fresh water and food, the exuviae remaining being recorded. The average time at which any given stage was reached was taken as the mid-point of the 6-hr. period within which the number of individuals that had completed the previous stage reached 50 per cent, of the total that finally did so.The curve relating temperature and time of development from newly hatched larva to adult is hyperbolic, except at the extremes. The later the instar, the lower is the temperature at which growth is most rapid. The threshold of development was between 9° and 10°C., the developmental zero 13.3°C., and the average thermal constant (between 16° and 32°C.) 2,741 degree-hours. The highest and lowest temperatures permitting development from newly hatched larva to adult were 36° and 14°C., respectively. The average durations of the four successive larval stages and the pupal stage, expressed as percentages of the time taken for newly hatched larvae to reach the adult stage, were 14.6, 13.9, 17.5, 33.3 and 20.6, respectively.
Taste receptors which evoke ingestion of blood in the mosquito, Aedes aegypti L., are stimulated by adenosine tetraphosphate, adenosine triphosphate, and adenosine monophosphate, in decreasing order. No other nucleotide is effective. Certain chelators can partially simulate the effect of nucleotides. The feeding response is elicited only at an osmotic pressure close to that of blood, and requires the presence of sodium ions.
Earlier investigations of the effects of extreme temperatures on different stages of Aëdes aegypti (L.) were supplemented by studies of eggs, larvae and pupae in water, and of eggs and adult females in air at various relative humidities.Larvae of the same stage, young pupae (defined as those less than half-an-hour old) and old pupae (at least 36 hours old), in groups of 100, 25 and 25, respectively, were kept for various periods at low temperatures in incubators, or, at high temperatures in glass cylinders closed at their lower ends by cloth filters and inserted into water baths, and then transferred to water at 28°C. and the mortality determined from the numbers surviving 24 hr. later (in the case of larvae) or becoming adult (in the case of pupae). Eggs in batches of 1,000 were similarly treated, except that periods of 24 hr. in water at 28°C. with yeast as food added were alternated with 24-hr. periods of drying, and mortality determined on the number that hatched and survived to the third or fourth stage. Adult females (four days old) were exposed in groups of 50 for various periods in jars over appropriate solutions giving a complete range of relative humidities and kept at low, medium and high temperatures. Eggs in batches of 1,000 were subjected to the same treatments. The adults were kept at 28°C. and 60 per cent. R.H. before treatment and for 24 hr. afterwards and mortality then determined. Mortality of eggs was determined after alternate 24-hr. periods of wetting and drying at 28°C., as in the case of eggs treated in water. The results of all the experiments were expressed as the exposure-times required to give 50 per cent. mortality (T50), calculated from the observed data.
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