Effects of dietary variation on lignocellulose degradation and physiological properties of Nicobium hirtum larvae

Abstract

We investigated the feeding behavior of larvae of the wood-destroying beetle Nicobium hirtum (Coleoptera: Anobiidae), an important wood pest in Japan, to determine the effects of dietary variation on lignocellulose degradation and larval growth and survival. Cultured colonies of N. hirtum larvae were fed artificial diets containing various amounts of starch (20, 50, and 80 wt%) mixed with hardwood (Shorea) lignocellulose. The polysaccharide degradation by N. hirtum was determined by chemical analyses of the initial artificial diets and fecal residues collected during the feeding experiment. Starch was preferentially decomposed when the larvae were fed the high-starch diet, whereas the decompositions of cellulose and hemicelluloses were more prominent when the larvae were fed medium- or low-starch diets. The larvae’s size and survival were recorded periodically to determine the diets’ effects on larval development. The survival rates ranged from 60 to 87% and were highest for the larvae fed the medium-starch diet and lowest for those fed the high-starch diet. Body size was highest in the larvae fed the high-starch diet. Fecal size increased along with the larval size increase. Overall, these results suggest that although starch is an essential carbon source for N. hirtum larval growth, lignocellulose also plays a key role as a nutrient that maintains the physiological activities of N. hirtum larvae and enhances their survival.