OK, who loves cockroaches? No one! Well, Ensign Wasps do and when you see one, you know they are on the hunt. These small active wasps are not hard to distinguish from the many small insects that can be found flying about in your home. They are harmless and interesting to watch as they seek their victims.
What makes Ensign Wasps stand out is their curious behavior of actively flagging their flattened, oval abdomen (gaster) up and down as they walk along whatever surface they land on. An ensign is another name for a flag. Our larger species, the Blue-eyed Ensign Wasp, is also dark in color, but only about 1/4 to 1/2 inches long.
The origin of these wasps is uncertain, likely Asia, but they are common across the tropics and subtropics where they have plenty of roaches to hunt. Their goal is not the roaches themselves, but the egg cases within which they lay their eggs. In the insect world, they are one of many parasitoids, insects that lay their eggs on or in the bodies of other arthropods, mostly other insects. The larvae that hatch go on to devour the host. In all cases, the host dies.
The behavior of Ensign Wasps once they locate a roach egg capsule (ootheca) has been documented many times and involves a drawn-out process. The female wasp must penetrate the tough integument of the capsule (a task that can take a long time) before laying a single egg inside. The larva that hatches is well-equipped to devour all of the eggs within before it metamorphosizes into an adult wasp.
On the menu are the typical suspects, including our American Cockroach and other larger-sized relatives that typically live outside our homes. What we get to see is the drama within our homes. We may never see the act of laying an egg, but at least we know they are on the prowl. And yes, if you spot an Ensign Wasp in your home, you have roaches. It is the South – get over it!
And in case you are wondering, there are other predators and parasitoids of roaches. The Emerald Cockroach Wasp also hunts roaches, that it stings, hauls to a nest, lays an egg, and searches for more for the next egg. As for other common natural predators, toads and frogs love roaches. Not something you want in your home, but certainly having these cool creatures in your yards may limit the number of cockroaches that make it into your abode.
There are several videos online of Ensign Wasps flagging their gasters and laying eggs. But seeing one in person is the best and not anything to be alarmed about. Just take the time to watch the show.
Hope to see you in our great outdoors!
Photo courtesy of Sharon Milligan