Synergistic defensive effects of raphides and cysteine protease.

Neonate Eri-silkmoth larvae (1.5 mg) were fed leaves of their host plant (castor oil plant) together with raphides, bromelain or both for 1 day, and the larval mass (average ± SD) and mortality were measured. Values of larval mass not followed by the same letters are significantly different (P<0.01; Tukey's test for multiple comparisons). The definition of the unit for protease activity is based on casein digestion, and is described in Materials and Methods.