Effects of larval density on larval survivorship and imaginal fecundity of Dacne picta (Coleoptera: Erotylidae)

Abstract

Adults of Dacne picta (Coleoptera: Erotylidae) show heavy aggregation in the field and they also vary considerably in size. To investigate the factors influencing the size and the effect of larval density on post-embryonic development and adult size, we conducted a laboratory experiment in which we varied the food quantity available to each larvae. The stage of larvae most critical for intraspecific competition was also estimated by the food consumption and adult size. Experimental manipulation of larval density revealed that adult size is affected by larval density, and adults of various sizes emerged from the high density plot. Larval density had no effect on pupation, though there was severe intraspecific competition at high densities. Thus, the typical competition among larvae was considered to be of the scramble type, but it changed to contest at extremely high larval densities. For female adults, lifetime and lifetime fecundity were reduced with decreased size. These results suggest that the beetles show a mainly scramble competition of larvae, but emerged adults inevitably suffer reduction in reproductive traits.