BLOOD-FEEDING BEHAVIOR OF ADULT<i>AEDES AEGYPTI</i>MOSQUITOES

Abstract

1. General reactions of adult male and female Aedes aegypti to human beings in the laboratory are briefly described. 2. Males fly about for a long time in the presence of a human forearm in a cage, and they frequently land and walk about briefly on the skin. Although they touch their labella to the skin, they were seen to attempt to penetrate it. 3. When males were offered a choice between pools of sucrose and defibrinated sheep blood, they drank sucrose. 4. Most adult females take their first blood meal when they are 23 to 26 hrs old. As soon as a feeding site has been located, they lower their hind legs. 5. The behavior of the maxillary palps indicates the major phases of the normal blood-feeding act. When an acceptable substrate is encountered, the palps are suddenly raised. When penetration of the skin starts, the palps begin to move up and down rapidly. As soon as blood appears in the food canal, the palps abruptly stop moving. They begin to move again as soon as the fascicle begins to be withdrawn, and they continue to move until the fascicle is completely removed from the wound. 6. Females always insert their fascicles more slowly than they withdraw them. Engorement on blood varied from 45 to 225 secs. After taking a full blood meal, females will seek and rapidly take another 2 to 5 hrs after the first. 7. Before becoming fully engorged on blood, a female begins to excrete fluid from her anus and continues to do so for 2 hours after completing the meal. 8. Various surgical operations showed that females could take blood when all of their tarsal tips were removed and when all but two of their legs had been amputated. They could not penetrate the skin after their labella were cut off or when the labial sheath was removed, even though they could position themselves correctly on the skin and attempted to pierce. 9. Although females with both antennae removed can locate and feed upon a human forearm in a lighted insectary, they cannot do so in total darkness. 10. Females which had been glued to pins and oriented carefully on a human arm did not penetrate or take blood, probably because the angle for penetration is highly critical and was not approximated. 11. Aedes will land on and probe active Galleria larvae and Hyalophora adults but do not obtain hemolymph from them. Although females can imbibe hemolymph from heat-fixed Galleria larvae, they actively reject heat-fixed hemolymph when their proboscides were forced into it. 12. Fasting Aedes females did not approach or attempt to probe normally resting or immobilized adults which had just engorged on either a young chick or a human being, except for one case involving very close confinement. Some fasting females were observed to take varying amounts of blood from immobile adults which had been heated to 42° C, but only after a lapse of 7 to 22 mins.