Silicon: an indigestible marker for measuring food consumption and utilization by insects

Silicon (Si) is a useful indigestible marker in plants for measuring food consumption and nutritional indices. Si concentrations in HF:HCl extracts of small (5–20 mg) samples may be measured easily using atomic emission spectroscopy. The Si marker and gravimetric methods were compared using Lymantria dispar (L.) larvae fed artificial diet with 2.5% silica (SiO 2 ). Both methods produced equivalent measures of consumption and nutritional indices. The Si marker method was also used to measure the consumption of six grass species by larvae of Paratrytone melane Edwards. The results were similar overall when compared with estimates of consumption based on total fecal weight, but varied significantly for some grass species. The Si marker method may be a useful alternative to the gravimetric method, especially in field situations.