Advances in rearing techniques have made it possible to produce them economically in large numbers, which has encouraged their commercialization. Insect-attacking nematodes have a life cycle consisting of an egg, four juvenile stages and the adult. Both steinernematid and heterorhabditid nematodes have a specialized third juvenile stage, the dauer larva, or infective juvenile, which is the stage which attacks insects. It is nonfeeding, and thus can survive in the soil for extended periods until it is able to find a susceptible host. Third stage dauer larvae are the stage which is used for field applications of nematodes.
Nematodes find hosts by orienting to carbon dioxide, and host excretory products.
These nematodes carry specific species of bacteria in their intestines. Upon entering the host, the nematode releases the bacteria into the host, where they rapidly multiply. The bacteria kill the host through release of protein-destroying enzymes, usually within 24 hours. Nematodes feed on the host remains, and complete two or three generations inside the host. When the host resources are gone, large numbers of infective juveniles leave the host and begin to search for new hosts.