In the body cavity, the mermithid absorbs food directly through its cuticle. Inside the host, mermithids can grow up to 50 cm in length. It is generally presumed that mermithid parasites of insects can significantly reduce their host population and thus are excellent candidates for biological control of insects. Steinernematidae An infective juvenile of S. carpocapsae . Steinernema carpocapsae may kill its hosts in 48 hours and has a very wide host range.
Infective juveniles are resistant to desiccation and can survive in damp soil for several months.
The nematode may also enter the host through the spiracles and penetrate the tracheae. In the host hemocoel, the nematodes release bacteria, which kill the host by septicemia within 48 hours. The nematodes feed on the Xenorhabdus bacteria and the host tissues. The nematodes develop rapidly to the adult stage, mate, and produce eggs. As soluble nutrients in the cadavers are depleted, the progeny of the second and third generations develop into infective juveniles, which exit from the cadaver and seek new hosts.