Population Dynamics of Acanthomia Spp. (Hemiptera, Coreidae) on Beans and Pigeon Peas in the Arusha Area of Tanzania

Abstract

Field experiments and observations were conducted on beans and pigeon peas between 1966 and 1967 to assess field population densities of A. tomentosieollis and A. horrida. The sampling and analysis methods are explained and their shortcomings pointed out. The data from these experiment:It showed that:- (a) The distribution of both species in the field is uneven, especially so on beans. (b)A. tomentosieollis occurred on both beams and pigeon peas, but A. horrida was found on beans and rarely on pigeon peas. (e) Higher densities of A. tomentosieollis were recorded on pigeon peas than on beans. (d) The method of sampling and analysis used proved inadequate in supplying accurate information on the duration and survival of the instars. Nevertheless~ the duration of the instars in the field appeared to be about the same as in the laboratory at comparable temperatures. For accurate information daily sampling is recommended. (j) These species maintain themselves throughout the year by changing plant hosts, from beans to pigeon peas to Dolichos lablab and back to beans.(h) Two parasites, one of A. tomentosieollis (and possibly A. horrida) eggs and one of A. horrida adults were found. Hadronotus gridus (egg parasite) was widespread and appeared to be more numerous when A. tomentosieollis population was low and concentrated in small areas than when the population was high and spread over large areas.