Abstract
I investigated inter- and intra-shoot distributions of the caterpillars of the ramie moth Arcte coerulea in shrubs of the host plant China ramie, Boehmeria nipononivea. The caterpillars were distributed on long shoots in the canopy of ramie, and caterpillar performance was better when they fed on leaves of the canopy shoots rather than those of the understory shoots. This was probably because the caterpillars could overcome the host plant defense to obtain nutrition from the sunlit shoots, which often contain higher concentrations of chemical defenses. Within a shoot, caterpillars were found on leaves that had just completed expansion. This leaf preference was probably affected by the change in food quality with leaf age. Caterpillars were never observed on buds, and their performances were poor when they fed on buds. This suggests that the chemical defense is heavily concentrated in buds. Outbreaks of A. coerulea frequently occur and cause defoliation of host plant shrubs; this may have resulted in accelerated evolution of host plant defense for rapid regrowth of the foliage, which contributes to the plant's tolerance of these moth caterpillars.
