Abstract
To determine the effect of xylem hardness and larval body size on the pupal-chamber tunnels (hereafter PCTs) made by Monochamus alternatus, newly hatched larvae were inoculated on Abies sachalinensis, Picea jezoensis, and Pinus densiflora logs and reared in the laboratory. After most larvae had developed well, larval body size and PCT size were measured. Larval body mass was significantly heavier in P. jezoensis and P. densiflora than in A. sachalinensis. ANCOVA with larval body mass as a covariate indicated that the adjusted mean of the median depth of the PCTs was greater in A. sachalinensis and P. jezoensis than in P. densiflora and that the adjusted mean of the PCT length was greater in P. jezoensis than in the two other tree species. P. densiflora xylem is known to be harder than the two other conifers. Consequently, it can be concluded that larvae of equal body mass make deeper and longer PCTs in soft xylem than in hard xylem.
