Evaniidae

Evaniidae, commonly known as ensign wasps, is a small family of parasitoid wasps in the superfamily Evanioidea. They are distributed worldwide, with greatest diversity in tropical regions, and are often found in environments where cockroaches occur, including human dwellings.

The most distinctive feature of evaniids is their peculiar body plan. Adults are small and typically dark in color, and their metasomal abdomen is slender and attached high on the thorax, carried erect like a tiny flag or ensign. This "flag-like" abdomen contrasts with the rest of the body and is the source of their common name. The wings often show the reduced venation typical of many parasitic wasps, and the tarsi and other leg segments are adapted for short flights and perching.

Biology and host relationships are central to evaniids. Females oviposit by inserting eggs into cockroach oothecae (egg cases) or into the eggs inside the ootheca. The developing larvae feed on the cockroach eggs, completing their life cycle within or near the ootheca. Because their brood attacks cockroach eggs, evaniids are considered beneficial for natural pest control, although their impact in urban settings is variable and often limited by the accessibility of oothecae.

Systematics and diversity place Evaniidae within the order Hymenoptera and the superfamily Evanioidea, alongside related families. The group comprises multiple genera and numerous species, with ongoing revisions in classification as new taxa are described and relationships clarified. Evaniidae are not typically pests of humans and are valued for their role in suppressing cockroach populations.