Hunting cockroaches: Seek and destroy

Frank Meek • Contributor

Who loves cockroaches? I do. They’ve provided me — and many of my fellow pest management professionals (PMPs) — with a comfortable living

for many years. But we’re not alone in our love of these insects. We’re not the only ones who like to hunt, find and destroy the roach. There are natural enemies for almost every animal on the earth, and the cockroach is no exception.

Vertebrate and invertebrate species are among the cockroach predators. Vertebrate predators include amphibians, such as frogs, and reptiles, such as snakes. Additionally, we know birds and some mammals consume them, too. Rodents and humans are among the mammals that will eat them; and in some areas of the world, cockroaches are considered food and even have medicinal purposes.

There are several invertebrates that love hunting these insects. For example, some small parasitic wasps lay their eggs in the egg sacs of the cockroaches, so the wasp larvae can live off the roach embryos until the wasp pupates. Then they emerge from the cockroach ootheca as adult wasps. One of the best known is the cockroach egg case parasite (Aprostocetus hagenowii), a small (0.4 to 6mm) wasp that attacks the ootheca of larger cockroaches, such as the American, Oriental and Australian species. This wasp will place as many as 70 eggs inside an egg sac. Another egg case parasitic wasp, Anastatus floridanus, will produce as many as 300 wasps from one egg sac.

There are also larger wasps that use adult cockroaches as food for their offspring. In the 10th edition of the Mallis Handbook of Pest Control, Dr. Coby Schal says the emerald cockroach wasp, Ampulex compressa, hunts American roaches and injects venom into their brains to create
a zombie apocalypse world for the roach. The wasp then leads the roach into the nest, where the wasp places an egg on the victim, and the young larvae consume the roach alive (Chapter 2, page 234).

The crab spider is another interesting cockroach predator. At one time, they were sold as biological control agents for cockroaches. It didn’t go over well with the public, however, because crab spiders are larger than the German roaches they were placed to kill.

There also are several noninsect predators, such as nematodes, which have been known to impact cockroach populations — not from a point of killing them as much as slowing down their reproduction rate. An infected cockroach reaches sexual maturity more slowly. There also are numerous bacteria, fungus, protozoa and viruses that can reduce or control populations of cockroaches.

Fungus compounds, such as Metarhizium anisopliae, have been used in the past to control populations in some settings, but the results were slow to come about. There’s still work being done with this and other natural materials to find how they might fit into a pest control program. As with all aspects of our work, the research goes on. pmp