Once the caterpillars pupate, the larvae themselves pupate, killing the Polyphemus pupa. The host remains alive until the parasitoid larvae pupate or emerge as adults. Male larvae pupate after the last moult, but females directly become neotenous adults. After undergoing three separate molts, the larvae pupate, then emerge as adults. Last instar larvae are able to travel significant distances before they pupate. The larvae tunnel in the pith where they feed and pupate. Larvae usually pupate just beneath the wood surface and eclose in mid to late summer. The fully grown larvae leave the water and spin a cocoon in which to pupate. In time, the spider will die, and the mature wasp larva will then pupate. The larvae there pupate from July to August. Larvae that feed on wood will pupate in the tunnels they have constructed. However, promethea silkmoth caterpillars pupate in trees. The larvae feed and wander for several weeks before finding an isolated spot to pupate. Mature larvae migrate to the soil, where they pupate for 12 to 16 days. When mature, they burrow underground and excavate a chamber where they pupate.