Trigonalidae

Trigonalidae is a family of parasitic wasps in the suborder Apocrita. They are the only living members of the superfamily Trigonaloidea. Trigonalidae are divided into 2 subfamilies; Orthogonalinae and Trigonalinae. These wasps are extremely rare, but surprisingly diverse, with over 90 species in 16 genera, and are known from all parts of the world. It is possibly the sister group to all Aculeata.

== Ecology == What little is known about the biology of these insects indicates a remarkably improbable life history: in nearly all known species, females lay thousands of minute eggs, "clamping" them to the edges of, or injecting them inside leaves. The egg must then be consumed by a caterpillar. Once inside the caterpillar, the trigonalid egg either hatches and attacks any other parasitoid larvae (including its siblings) in the caterpillar, or it waits until the caterpillar is killed and fed to a vespid larva, which it then attacks. If the caterpillar is neither attacked by another parasitoid nor fed to a vespid, the trigonalid larva fails to develop. Therefore, they are parasitoids or hyperparasitoids, but in a manner virtually unique among the insects, in that the eggs must be swallowed by a host, and even more unusual in that there may be an intermediate host. A few species are known exceptions, which directly parasitise sawflies.