Abstract
A technique for rearing Neodiprion sertifer (Geoff.) in individual isolation from egg to adult is described. Larvae so reared under optimal conditions experience mortality only slightly greater than that sustained by larvae growing in the normal feeding aggregations. The comparative capacity of the isolated larvae to withstand even slight departures from optimal conditions of food, temperature and humidity is low. These observations together with data on the responses of isolated and normal larvae to physical factors are discussed in their ecological context.