Did You Know? 17 Incredible Ensign Wasp Facts

Ensign wasp facts, explore the friendly pest control wasp.

Have you seen a black insect that resembles a fly in your house, eating cockroach eggs? Yes, you heard it right. These are ensign wasps, and they play a significant role in controlling the population of cockroaches. Also called nightshade wasps or hatchet wasps, they belong to the family of parasitic wasps. It must be intriguing why they are called ensign wasps. Ensign means a large flag on a ship, indicating the nationality of the ship, usually flown at the rear side or stern of the ship. The abdomen of this wasp resembles an ensign, which is constantly moving up and down like a waving flag, giving it the name ensign wasp.

The larva of this wasp develops inside the cockroach egg case called ootheca, feeding on the egg completely. They prey on dozens of such cockroach eggs and manage to control the cockroach population. Although lethal to the unhatched cockroach population, they do not bite or sting humans, good friends of ours, and their presence is helpful.

Ensign wasps belong to the order Hymenoptera; the Evaniidae family has about 400 species across 20 genera.

You can also learn about great golden digger wasps and mud dauber wasps in our other articles.

Ensign Wasp

Fact File

What do they prey on?

Nectar, Honeydew

What do they eat?


Average litter size?


How much do they weigh?

0.000063-0.00035 lb (29.7-159.0 mg)

How long are they?

0.25-0.75 in (6.5-19 mm)

How tall are they?


What do they look like?


Skin Type


What are their main threats?

Beetles, Dragonflies, Moths, Centipedes, Larger Wasps

What is their conservation status?

Not Extinct

Where you'll find them

Human Habitats


All over the world except polar regions





Scientific Name





Has 20 genera

Ensign Wasp Interesting Facts

What type of animal is an ensign wasp?

An ensign wasp is an insect belonging to the Evaniidae family; a parasitic wasp commonly shows this predatory behavior.

What class of animal does an ensign wasp belong to?

The ensign wasp is an arthropod belonging to the class Insecta. Its order Hymenoptera, Evaniidae family, and has about 400 species.

How many ensign wasp are there in the world?

The ensign wasps are everywhere in the world except in the polar region. Though the number of these insects is unknown, we know that the Evaniidae family has about 400 species. Although two Evaniidae species, Evania appendigaster, and Prosevania fuscipes, are practically distributed worldwide and feed on insects that are considered pests, their populations do not grow in significant numbers population of cockroaches far outweighs these wasps. Hence they fail as effective biocontrol agents. However, in such places, Evaniidae wasps show up effectively.

Where does an ensign wasp live?

Ensign wasps are everywhere in the world except in the polar regions. One common species, Evania appendigaster, is of East Asian origin, currently wide-ranging in tropical and subtropical areas of the world, northward into Palearctic and Nearctic regions. It is common in the United States.

What is an ensign wasp's habitat?

Ensign wasps are found primarily in areas around human settlements where there could potentially be an infestation of cockroaches and their eggs. They are found in households, business houses, around human habitats. Their habitats include outdoors on the forest floor, piles of wood, tree holes, etc. They are also found near flowers such as parsley, fennel, and honeydew as they feed on nectar.

Who do ensign wasp live with?

The ensign wasps are solitary beings found where there are cockroaches and their eggs rather than other wasps. They do not build hives or nests. But some species of wasps live in colonies like hornets. These are social wasps that build nests.

How long does an ensign wasp live?

The ensign wasp adults have a life span of two to three weeks.

How do they reproduce?

Ensign wasps lay eggs in the oothecae, egg cases, of woods,  and other cockroach species in the family Blattelidae.

A female ensign wasp lays a single egg after locating the oothecae, the cockroach egg case. Once it finds the cockroach ootheca, the female vibrates her antennae over it, lying parallel to the long axis of the egg case. After about 15 to 20 minutes of hard work and wriggling, she penetrates through the touch shell of the egg case and inserts her ovipositor.

The developing wasp larvae undergo five molts, during which they eat all the cockroach eggs inside the cockroach egg cases and prevent any cockroaches from emerging. The larva can grow up to 0.3 in (8 mm) in length and pupates within the ootheca. Once it matures, the adult leaves the egg case making a hole in one corner of the long side of the case.

What is their conservation status?

Ensign wasps are Not Extinct, according to the IUCN, they are distributed worldwide, and their presence in North American regions is common.

Ensign Wasp Fun Facts

What do ensign wasps look like?

Ensign wasp facts, meet the harbinger of cockroaches to control them.

Ensign wasps, when adults, are usually entirely black, with contrasting blue eyes, having two pairs of wings and three pairs of legs. They are usually about 0.25-0.75 in (0.63-1.9 cm) long, and sometimes, their appearance resembles spiders due to their black color and long legs on the thorax. Their legs have 12- 13 segments. The abdomen is oval or somewhat triangular, resembling a flag, and moves up and down, which is why ensign wasp. This abdomen is attached high on the thorax by a narrow or cylindrical waist or petiole. They also have chewing mouthparts or mandibles to chew foods.

The larva can grow up to 0.31 in (8 mm) in length and comes out of the egg cases of cockroaches after it pupates and becomes an adult.

How cute are they?

Ensign wasps are not very cute by appearance, but the function of pest controlling makes their presence wanted in the households.

How do they communicate?

Wasps, in general, communicate through pheromones, smell hormones released outside the body. These chemicals have a specific smell that alerts the other wasps about impending danger from predators or attracting mates.

Ensign wasps are solitary, and their primary communication is through their antennae, without which, they would be deaf. The antennae have short, sensitive hairs which can sense touch, smell, and hear. They also have flagella at the tip of the antennae, which aids in hearing and smell.

How big is an ensign wasp?

The length of ensign wasps is about 0.25-0.75 in (6.5-19 mm). Thus, the size could be almost double the size of a housefly.

How fast can an ensign wasp fly?

Though the exact speeds of this insect are not known, ensign wasp fly really fast to the extent that it may be difficult for you to capture.

How much does an ensign wasp weigh?

In general, the weight of wasps varies significantly from site to site. But it is found that wasps can weigh from 0.000063-0.00035 lb (29.7-159 mg), with an average of 0.00027 lb (103.1 mg). So they are really lightweight insects.

What are their male and female names of the species?

The male of this species is called the male ensign wasp, and the female is called the female ensign wasp.

What would you call a baby ensign wasp?

The life cycle of hatchet wasps consists of egg, larva, pupa, and adult Hatchet wasp.

What do they eat?

The adult ensign wasp feeds on nectar and honeydew from flowers such as parsley, fennel, honeydew, etc. The wasp larva is a parasite feeding on eggs in cockroach egg cases.

Are they poisonous?

Neither the ensign wasp bite is poisonous, nor is the ensign wasp sting is dangerous. They do not harm humans. However, they are a threat to cockroaches.

Would they make a good pet?

Though they are harmless to humans, the hatchet wasps are not known to be good pets. However, their presence in the house helps restrict the cockroaches. In addition, it is a parasitic wasp that is beneficial to us in controlling pests. So, it is better not to get rid of the ensign wasps.

Did you know...

It is impressive to know through fossil studies that ensign wasps existed for the last 20 or 30 million years without getting extinct!

How many ensign wasps live in a group?

Some species of wasps, like hornets and paper wasps, live in colonies. As a result, the colony sizes can vary significantly. For example, paper wasps form colonies of 25, which can grow to 100. The common yellow jacket can form a colony of larvae from 3000 to 8000 in a nest. These social wasps support each other in finding food sources, sensing predators, etc.

How did ensign wasps get their name?

Ensign means a large flag on a ship, indicating the nationality of the ship, usually flown at the rear side or stern of the ship. The abdomen of this wasp resembles an ensign, which is constantly moving up and down like a waving flag, giving it the name ensign wasp.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other arthropods from our flesh-fly fun facts and European paper wasp facts pages.

You can even occupy yourself at home by coloring in one of our free printable ensign wasp coloring pages.



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