Factors influencing ingestion of particulate materials by mosquito larvae (Diptera: Culicidae).

Relative ingestion rates of mosquito larvae, as indicated by the number of substrate-filled gut segments per unit time, were determined for Culex tarsalis Coquillett, Aedes aetypti L., and Anopheles albimanus Wiedemann. Among the three species, Ae. aegypti larvae were the most rapid feeders. F50 (median time for complete repletion of 50% of the larvae) was 61, 42, and 100 min for the three species feeding on a wheat flour suspension, respectively. Food particles with nutritive values (dried yeast, wheat flour, fishmeal, or dried blood) were ingested faster than inert particles (kaolin, talc, chalk, or charcoal). The addition of aqueous yeast extracts containing phagostimulants accelerated the ingestion of inert particles. Increasing the concentration of inert particles did not increase ingestion rates. Larval age, water temperature, and starvation, but not larval density, influenced rates of ingestion. Younger instars were more rapid feeders than older instars. First instars of the three species filled their guts with wheat flour approximately two times faster than fourth instars. Increasing water temperature from 18 to 31 degrees C accelerated wheat flour ingestion by fourth instars of Cx. tarsalis, Ae. aegypti, and An. albimanus by factors of 1.9, 1.5, and 1.7, respectively. After starvation for 12 h, fourth instars of Cx. tarsalis and Ae. aegypti increased ingestion of wheat flour about 1.6 and 1.8 times, respectively. In contrast, starvation of An. albimanus larvae for the same period resulted in decreased wheat flour ingestion by 2.2 times when compared with unstarved larvae. These results indicare that, in addition to the chemical factors associated with the food substances, the physiological and environmatal conditions of the larvae play an important role in regulating the ingestion rate of suspended particles by mosquito larvae.