The Apocrita differ from the Symphyta in having a constricted base of their abdomen. The thorax appears as for segments with the propodeum being the first abdominal segment fused with the thoracic segments. The hind wings do not have more than two basal cells. The larvae are usually grub like or maggot like and vary in feeding habits; some are parasitic or predatory on other insects, while others are phytophagous. The adults feed primarily on flowers, sap, and other plant materials; some of the parasitic species occasionally feed on the body fluids of the host in a behavior known
As "host feeding."
Many species in this are parasitoids in the larval stage on other insects (or other invertebrates) and, because of their abundance, are very important in the natural balance of insect populations. Most of the parasitic Apocrita lay their eggs on or in the body of the host, and many have a long ovipositor with which hosts in cocoons, burrows, or other protected situations may be reached. In some cases only a single egg is laid on a host; in others, several to many eggs may be laid on the same host. A single parasitoid attacking a host usually pupates inside the host; where there are many parasitoids in the same host, they may pupate inside it, on the outside of it, or entirely away from it. Some species are parthenogenetic. Polyembryony is found in a few species. Some of the parasitic species are hyperparasitoids (Borror et al. 1989).