Why Are Cockroaches Believed to Be the Oldest Insect?

Written and verified by the vet Érica Terrón González

Last update: 22 December, 2022

Cockroaches are said to be one of the oldest insects on the planet. This is because fossil remains have been found that are more than 200 million years old! These insects belong to the Blatodean family, which includes more than 4,500 species, and most of them live in tropical areas.

They often live hidden in cracks or other inaccessible corners of the house, as well as under stones or in the bark of trees. And they only go out to feed at night.

Some species are mainly found around humans, living near garbage cans, drains, or even in the kitchen or bathroom.

Origin and evolution

The first fossils relating to cockroaches date back to the Carboniferous period, about 300 million years ago. But later research has shown that these fossils are not only the beginnings of the Blatodean family, but also mantises and termites.

Therefore, the cockroach’s true origins date back to the early Cretaceous period. In fact, there’s enough evidence to suggest that current termites evolved from the primitive cockroaches that were around during the Jurassic and Triassic periods.

In fact, cockroaches belonging to the Cryptocercus genus are more closely related to termites than to other families of cockroaches.

General characteristics of cockroaches

Cockroach morphology

Cockroaches are flat, oval-shaped insects. They have wiry antennae, small eyes, and a body and head protected by a hard shield. Their legs are long, flat, and prickly, and some species have large, translucent wings. They also chew their food.

Diet

Cockroaches are omnivores and will eat almost anything. Just like termites, they can’t digest cellulose by themselves but they have digestive microbiota to help them.

There have been cases of cockroaches allegedly surviving exclusively on the glue used in binding books or used on postage stamps.

Reproduction

Female cockroaches lay eggs that have hard shells. Some species carry these eggs attached to their abdomen until the larvae are close to hatching. Other species deposit them somewhere safe. The incubation period varies between 15 days and 3 months, depending on species.

Newly born cockroaches don’t take long to resemble adults, but their wings are poorly developed.

Which are the most common species?

The German cockroach (Blatella germanica) has spread from Europe to almost every part of the world. It’s much smaller than the American cockroach (Periplaneta Americana), measuring between 0.5 to 0.6 of an inch.

They live around human activity and are considered a pest. The only place they haven’t reached is Antarctica.

The American or red cockroach is originally from the African tropics but is now all over the warmest parts of the globe. They can measure up to an inch and a half long and are one of the largest urban cockroaches.

The Oriental cockroach (Blatta orientalis) likes to live in people’s houses and measures up to an inch long. They have a shiny body with dark brown and black shades.

One of their most common features is their sexual dimorphism. Males have two long wings that cover most of their bodies, which are narrower than the female body.

How come they can survive seemingly anything?

If cockroaches are one of the oldest insects in the world, it might have something to do with the fact that they’re capable of surviving certain things that other animals simply can’t, such as the dinosaurs, for example.

Cockroaches are some of the toughest animals on the planet and some species can even survive for a month without food.

They’re able to survive on very limited resources, eating whatever they find within their reach. They can even live without air for 45 minutes and slow down their heartbeat.

And this is why they can live for up to a year, which is something unheard of in other insects.

It’s often casually said that, if there were an apocalypse, cockroaches would easily repopulate the earth. Even after a nuclear war, their resistance to radiation would be greater than that of any invertebrate.

This ability to survive is down to cell renewal. Cells that divide are more vulnerable to the effects of radiation, but cockroach cells only divide once when shedding their skin. As a result, they’re more resistant.

However, it takes up to 48 hours for a vertebrate’s cells to completely divide, which leaves them much more vulnerable to radiation.