Spatial Distribution of Flying Southern Pine Beetle (Coleoptera:Scolytidae) and the Predator Thanasimus dubius (Coleoptera:Cleridae) 1

Abstract

Spatial dispersion patterns of flying southern pine beetles, Dendroctonus frontalis Zimm., and the clerid predator Thanasimus dubius (F.) were determined within 3 natural infestations of southern pine beetle (SPB) in eastern Texas using grids of sticky traps. There was significant positive association of the 2 insects throughout the trapping grids, although aerial population densities of the clerid were inversely related to aerial densities of SPB. Aggregation patterns were quantified using the index of patchiness (IP) and the regressions of mean crowding (M*) on mean density ( m ). Both methods showed a highly clumped pattern for both beetle species. SPB density in the infestations was positively associated with the daily rate of tree attack by the beetles, but the degree of population aggregation in the infestations was inversely related to the daily rate of tree attack. Although densities of the two species did not follow the same trends among the 3 infestations, the degree of aggregation did (i.e., SPB was most highly aggregated in the location where T. dubius was most highly aggregated) and Lloyd's index of interspecific patchiness indicated overlapping aggregate distributions. A kairomonal response mechanism for T. dubius , and SPB co-aggregation within infestations is hypothesized.