Cockroaches are one of the early groups to appear in the history of insect evolution. The oldest cockroach fossil is about 350 million years old. The oldest heaxpod fossil is about 415 million years ago, so cockroaches have been on earth for most of insect history. Cockroaches predate many modern groups of insects such as beetles flies, wasps and moths. Cockroaches predate the dinosaurs by about 150 million years.

Cockroaches have survived some of the largest and most catastrophic extinction events in earth history. The end of the Permian extinction is the only known mass extinction of insects. At least 8 groups of insects went extinct. Cockroaches survived this event.

Species that depend on living plants are not likely to survive an extinction if their plant hosts are extinct. However, cockroaches primarily feed on dead or decaying plant material. Extinction events leave dead plant and animal materials- plenty of food for cockroaches. Cockroaches feed on most dead plants, so loss of hosts is not an issue.

There are currently over 4000 species of cockroaches. Of these, less than a dozen are peridomestic (live in human structures). Even some of the occasional pest cockroaches such as the Oriental cockroach and the American cockroach commonly live outdoors. In considering some of these occasional indoor pests, it is important to consider outdoor populations.

As a graduate student in Illinois, I rented a house with a mulberry tree just outside the back door. It was so close to the house that someone had notched the eaves to allow the tree to grow past the roof. (Why is this not a good idea?) The tree would drop mulberries over the back stoop in summer. The mulberries were supporting a thriving population of oriental cockroaches that would occasionally enter the house to forage. The problem came to a head when my wife was making oatmeal raisin cookies and the “raisins” started walking out of the bowl. Two hours with a saw eliminated that problem.

Eliminating the sources of food and water are the most important steps for keeping cockroaches under control.

Cockroach (Periplaneta spp. nymph) near a woodpile

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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