Dispersal of Larvae of the Tenebrionid Beetle, Zophobas Rugipes, in Relation to Weight and Crowding

When larvae of the tenebrionid beetle, Zophobas rugipes, were allowed to disperse among 26 equivalent chambers in a circular dispersarium, distribution patterns were found to be a function of larval weight and number of larvae in the apparatus (N). Small larvae (x wt 250 mg) were significantly aggregated while large mature larvae (, 1000 mg) were highly overdispersed. Medium larvae were intermediate, being overdispersed when N was 26 and showing some aggregation within general overdispersion when N was 52. Larval distributions did not deviate significantly from randomness when N was 13, indicating weak interactions at low density. The increasing tendency to overdisperse with increasing larval weight correlates with the parallel increasing tendency to pupate. Since metamorphosis of Zophobas rugipes larvae is known to be inhibited by crowding, this weight-related overdispersal probably allows pupation by mature larvae by causing them to leave regions of high population density.