ABSTRACT
Work on the factors controlling the avidity of Aëdes aegypti females for a blood meal previously reported by Seaton & Lumsden (1941) was continued.
Mosquitoes were kept after hatching for 96–120 hr. in darkness at about 25° C. and 80% relative humidity, and were then offered a blood meal on the human arm in darkness.
Wide variations in the light intensity during the few minutes’ manipulation immediately previous to offering the host did not significantly affect the numbers feeding.
The relative humidity of the environment at the time of biting appeared to be of little or no importance.
The optimum environmental temperature for biting was near 35° C. At 35° C., out of batches of ten mosquitoes offered 5 min. opportunity to feed, means of 8·8 ± 0·44 and 9·2 ± 0·33 fed at high and low humidities respectively.
Large proportions of A. aegypti females, confined within 8·5 cm. of a host and in darkness, were able to locate the host and to feed when environmental temperatures approximated closely to the skin temperature or even were above it. Some factor other than the presence of a temperature gradient rising to the skin must therefore be responsible for their orientation to, and probing of, the host.
In the majority of fed mosquitoes blood was found in the stomach alone, but partly fed mosquitoes showed a higher proportion with blood in the diverticula than did those fully gorged. Such an effect is probably due to regurgitation of blood from the stomach when feeding is interrupted before its normal completion.
