Evanioidea is a small Hymenoptera

Hymenoptera

Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...

n superfamily that includes three families, two of which (Aulacidae

Aulacidae

The family Aulacidae is a small cosmopolitan group, with 3 extant genera containing some 200 known species. They are primarily endoparasitoids of wood wasps and xylophagous beetles...

 and Gasteruptiidae

Gasteruptiidae

The family Gasteruptiidae is one of the more distinctive among the Apocritan wasps, with surprisingly little variation in appearance for a group that contains around 500 species in 9 genera worldwide. The propleura form an elongated "neck", the petiole attaches very high on the propodeum, and the...

) are much more closely related to one another than they are to the remaining family, Evaniidae

Evaniidae

Evaniidae, also known as the ensign wasps or hatchet wasps, is a family of parasitic wasps. It numbers around 20 extant genera containing over 400 described species, and is found all over the world except in the polar regions...

. There is a rich fossil record, however, that helps fill in the gaps between these lineages. They all share the trait of having the metasoma

Metasoma

The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circulatory system, and the apical segments are typically...

 attached very high above the hind coxae

Arthropod leg

The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

 on the propodeum

Propodeum

The propodeum is the first abdominal segment in Apocrita Hymenoptera . It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is strongly constricted posteriorly to form the articulation of the petiole, and gives apocritans...

.

It is a poorly-known group as a whole, with some 1100 known species in total, and a great many species are still undescribed. While each of the three families differs in biology, within each family they are remarkably uniform in appearance and habits.