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FIGURE 1. Most people see the ensign wasp as a dark-colored, erratic flying insect when viewed from a distance.

   
 

 

FIGURE 2. An up close view of an ensign wasp at rest reveals a colorful and striking insect.

   
 

 

FIGURE 3. The eggs cases of the pesty, indoor loving American cockroach serves as a food source for the developing young ensign wasp.

   

Quick Facts

Common Name:

Ensign Wasp

Genus / Species:

Evania appendigaster

Type of Beneficial:

Insect parasitoid

Type of Metamorphosis:

Immature stages appear different from adults (i.e., complete metamorphosis)

Beneficial Stage:

Larval stages only

Prey:

Eggs within egg case (ootheca) laid by cockroaches

Occurrence:

Widespread across the county and important parasite of cockroach eggs  

Mounted Specimen? 

Yes (mounted specimen for viewing available in insect collection at County Extension Office)

 

When answering telephone calls from the public in the Master Gardener office, you will hear many things. There was a one day I was at the Extension Office and overheard a fellow MG speaking to Dr. Johnson, our County Extension Horticulture Agent.. A lady had called to “inform the public” that she had discovered a new insect.

She stated it was seen at her house and at a local retail store in a mall. She also informed us that this new insect resembled a small cricket that could fly really well–to the extent that she had difficulty capturing one. Needless to say, it became quite a mystery to all of us in the office.

A couple of days later the mystery was solved! The lady managed to collect a specimen and her husband brought it to the office. Dr. J promptly identified the specimen for the gentleman as an Ensign Wasp. Dr. J then looked at me and said that this was wonderful opportunity for a budding entomologist to learn more about this insect and to spread the information to our residents.

Ensign wasps belong to a group of insects called Evaniidae. They are called ensign wasps because they have a small compressed, black abdomen that they often move up and down (it seems as if they were signaling with a small flag).

Adult ensign wasps are usually entirely black. They have three pairs of legs, two pairs of wings and are 1/4 to 3/4 inch long. They are easy to distinguish from other wasps. Sometimes they are thought to look like spiders because of their black color and their relatively long legs on a thorax. The abdomen, oval or somewhat triangular, is attached high on the thorax by a narrow, cylindrical petiole, instead of down near the bases of the hind legs.

Eleven species are known to occur in the U.S. and Canada. Evania appendigaster is the most conspicuous of these species, being the largest (forewing 1/4 to 1/3 inch in length) of all the eleven species in the U.S. and Canada.

Evaniids are solitary wasps that are sometimes called predatory, but actually they are parasitic since their young develop inside egg cases of cockroaches. Their typical habitat is outdoors on the forest floor, tree holes, piles of wood, palm bracts, etc., where most cockroaches deposit and conceal their egg cases (known as oothecae (plural form)).

However, E. appendigaster parasitizes the egg cases of the home-infesting American cockroach and so it can also be found indoors, where these cockroaches often occur. Females lay a single egg in each ootheca within one of the eggs, which serves as food for the first instar larva. The following four instars feed on, and eventually consume, the other eggs.

Pupation takes place within the ootheca, without a cocoon. At maturity, the adult cuts and escapes through a small hole near one of the ends of the cockroach egg case. Adult ensign wasps are normally outdoors. They are attracted to flowers and to honeydew, and live 2-to3 weeks. They do not bite or sting or feed on humans but they sometimes wander indoors. If so, just show this small, but beneficial insect back outdoors.

Another mystery bug solved!

Beneficials in the Garden & Landscape is an Earth-KindTM program coordinated through Extension Horticulture at Texas A&M University. Earth-Kind uses research-proven techniques to provide maximum gardening and landscape enjoyment while preserving and protecting our environment.

 

This web site is maintained by Master Gardener Laura Bellmore, under the direction of William M. Johnson, Ph.D., County Extension Agent-Horticulture & Master Gardener Program Coordinator.

All digital photographs are the property of  the Galveston County Master Gardener Association, Inc. (GCMGA) © 2002-2006 GCMGA - All Rights Reserved.