Effect of body size on host seeking and blood meal utilization in Anopheles gambiae sensu stricto (Diptera: Culicidae): the disadvantage of being small.

The survival, metabolic reserves, and host-seeking response of unfed Anopheles gambiae Giles sensu stricto females of different size classes were investigated from 1 to 6 d after emergence. In addition, the effect of blood meal size and frequency of feeding on the accumulation of metabolic reserves and reproductive development were investigated during the 1st gonotrophic cycle. Large females survived longer and contained significantly more protein, glycogen, and lipid at emergence than did small females. Over 6 d, the host-seeking response of large mosquitoes was greater than that of small ones. There was no gonotrophic development in unfed small females after emergence, whereas < or = 52% of large females developed oocytes to Christophers stage II. One blood meal, given by enema, resulted in gonotrophic development to stage II in small females, whereas only large females matured oocytes to Christophers stage V. In both large and small females, egg development was related to the size of the blood meal, but large females were better able to utilize the meals. Two successive blood meals enhanced the ability of small females to develop eggs. The pregravid condition commonly observed in An. gambiae appears to be determined by insufficient metabolic reserves at emergence, and the probability for small individuals to be pregravid is greater than for large mosquitoes because of the need to build up sufficient energy reserves before gonotrophic development can occur. The consequence of this behavior in relation to malaria transmission is discussed.