Host tree effect on the pupal chamber size of Monochamus carolinensis (Coleoptera: Cerambycidae)

Abstract

Most Monochamus carolinensis (Olivier) larvae over-winter in pupal chambers constructed in the trunk and branch xylem of host trees. The larval size of M. carolinensis and the pupal chamber size in the bolts of Pinus sylvestris and P. strobus were measured between December 1985 and February 1986 in Illinois. Larvae in P. strobus were larger and heavier than those in P. sylvestris. The pupal chambers in P. strobus were deeper and longer than those in P. sylvestris. The length and depth of the pupal chamber increased with increasing larval body mass for each pine species. Larvae of an equal body mass constructed 0.65 cm deeper and 0.95 cm longer pupal chambers in P. strobus than in P. sylvestris. Consequently, the difference in the length and depth of the pupal chamber between the two pine species was explained by the differences in the larval body mass and the wood hardness of the pine species. These results suggest that the host trees' wood hardness directly affects the length and depth of the pupal chamber and the inner bark has an indirect effect on them as a food resource.