Chrysididae (ruby-tailed cuckoo wasps, ruby-tailed wasps; suborder Apocrita, superfamily Bethyloidea)
Family (according to some authors, within its own superfamily, the Chrysidoidea) of wasps which are 6–12 mm long (although some are up to 22 mm long), with bright, metallic blue, red, or green bodies. The abdomen
has four segments, or fewer, and is concave ventrally. The hind wings do not have closed cells and possess a basal lobe. Adults lay their eggs in the burrows of solitary wasps
or bees (particularly mud-dauber wasps) and some parasitize symphytans. Most larvae are external parasites, development occurring only after the host is completely consumed, although some larvae are inquilines
and others feed on a provisioned supply of food. The adults, which do not sting, often curl up into a ball when disturbed. They are fairly common and their common names refer to the often bright-red abdomen of many species, and their parasitic and inquiline habits in the nests of solitary bees and wasps.