There is only a single family, Megalyridae, in this superfamily with 8 extant and 3 extinct genera. There are ca. 48 identified species. These insects are found primarily in areas of relict primary tropical forests, and there are very few American representatives. Australia has the most species.
There has been indecision on the definition of this family. Species now placed in Megalyridae have been classified into as many as six other families (Braconidae, Evaniidae, Ichneumonidae, Stephanidae, as well as Dinapsidae and Maimetshidae.
The species are distinguished by the fact that their mesothoracic spiracle has moved, and is located in the upper corner of the pronotum, though this is a difficult feature to see. A useful character is that the base of the antenna fits into a wide concave groove below the eye. Females of Megalyra have ovipositors ranging from 5-8.3 times the body length, but this is not true of the other genera.
The largest known species is the female of the Australian Megalyra shuckardi, with a body length of 25 mm and ovipositor length of 83 mm. The smallest known megalyrid is the Brazilian Cryptalyra plaumanni, with a body length of 2.7 mm and ovipositor 1.2 mm long.
Megalyrid wasps are believed to be idiobiont endoparasitoids of concealed insect larvae. One Australian species, Megalyra troglodytes, attacks the larvae of Arpactophilus mimi, a mud-nesting crabronid wasp. Oviposition is primitive, because they insert their ovipositor into pre-existing cavities, holes, or cracks, rather than drilling into the substrate as in other hosts.
Mason (1993) reported that there was only one family, Megalyridae, in this superfamily.
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Perrichot, V. 2009: Long-tailed wasps (Hymenoptera: Megalyridae) from Cretaceous and Paleogene European amber. Paleontological contributions, (1)
Shaw, S. R. 1988: Carminator, a new genus of Megalyridae (Hymenoptera) from the Oriental and Australian regions, with a commentary on the definition of the family. Systematic entomology, 13: 101–113.
Shaw, S. R. 1990: Phylogeny and biogeography of the parasitoid wasp family Megalyridae (Hymenoptera). Journal of biogeography, 17: 569-581. [Errata: Journal of biogeography, 18: 470]
Vilhelmsen, L., V. Perrichot & S. R. Shaw. 2010: Past and present diversity and distribution in the parasitic wasp family Megalyridae (Hymenoptera). Systematic entomology, 35(4): 658-677.