CONTEST AND SCRAMBLE COMPETITIONS IN CALLOSOBRUCHUS-MACULATUS (COLEOPTERA, BRUCHIDAE) .2. LARVAL COMPETITION AND INTERFERENCE MECHANISMS

Competition between contest and scramble strategists was examined using two strains of Callosobruchus maculatus, the contest strain (iQ) and the scramble strain (tQ). The direct larval interference experiment within each strain showed that the contest strain performed strong direct interference throughout its larval stage against the conspecific opponent(s). The scramble strain also performed its interference, but only during the 3rd and the 4th larval stages. The inter-strain larval competition experiments inside a large and small mung bean (Vigna radiata) showed that the contest strain was, in general, superior to the scramble strain in competition, but the competition results were density- and frequency-dependent. In the large beans, the proportion of adult emergence of the contest strain increased with the increase of its own initial density but decreased as the initial density of the scramble strain increased. The shape of the proportion of adult emergence became nonlinear in the small beans. The cause of the complexity of inter-strain competition results was discussed in the light of the difference in larval interference ability between the two strains.