Anopheles gambiae feeding and survival on honeydew and extra-floral nectar of peridomestic plants

Abstract

It is widely believed that the malaria vector Anopheles gambiae Giles (Diptera: Culicidae) rarely or never feeds on sugar in nature. If so, the need for supplemental blood-feeding may be increased and this would help to explain why it is such an efficient malaria vector. Nonetheless, both sexes of this mosquito species readily imbibe and digest sugar solutions, and sugar is a staple of laboratory colonies. In this study, we investigated whether An. gambiae will feed on the extra-floral nectar of three common peridomestic plants in Africa, and on honey-dew of the mealybug Pseudococcus longispinus (Targioni-Tozetti) (Hemiptera: Homoptera: Pseudococcidae), and how this affects survivorship. We found that both males and females of An. gambiae provided with vegetative parts of cassava (Manihot esculenta Crantz) survived as well (x̄ = 26.3 and 19.2 days, respectively) as they did on 50% sucrose solution (x̄ = 29.7 and 24.3 days, respectively) and much longer than they did on water alone (x̄ = 1.8 days, both sexes). Females provided with mealybug honeydew also lived substantially longer (x̄ = 16.5 days) than those on water alone. Males and females provided with vegetative parts of castorbean (Ricinus communis L.) also survived much longer (x̄ = 12.7 and 7.8 days, respectively) than on water, but those provided with flowering lantana (Lantana camara L.) did not. Anthrone tests of females after one night of exposure to these potential energy sources confirmed that they obtained fructose from cassava, from mealybug honeydew, and from non-flowering castorbean, but not from lantana or from castorbean lacking its petiolar nectaries. Previous laboratory studies had shown that sugar availability affects the survival and biting frequency of An. gambiae. It now appears that this mosquito can locate natural sources of plant sugar readily and utilize them effectively. Nectar-producing plants in the domestic environment may play a significant role in this mosquito's energy budget and malaria vectorial capacity.