the German cockroach conquered the world – DW – 05/24/2024

the German cockroach conquered the world – DW – 05/24/2024
the German cockroach conquered the world – DW – 05/24/2024

Most people find them disgusting, but their capabilities are surprising: cockroaches are lightning fast, can fit through cracks, and are capable of climbing even smooth, vertical surfaces.

But, above all, they are extremely resistant. Their shell supports up to 900 times the weight of their own body, making it very difficult to crush them. Furthermore, most insecticides have no effect on them.

That’s a big problem, because cockroaches can transmit a number of bacteria, viruses and fungi. These, in turn, can cause allergies, intestinal colds, hepatitis A, anthrax or tuberculosis, among other illnesses.

triumphant advance

The most widespread worldwide is the so-called “German cockroach” (Blattella germanica), present on all continents. The insect, active at night, can measure up to two centimeters and usually lives in homes and buildings, where it takes refuge in humid places. .

The German cockroach was first described in 1776 by naturalist Carl von Linné. Those were the times when, after the Seven Years’ War, half of Europe was in ruins and enormous poverty prevailed.

It is called the “German cockroach”, but its origin was unclear. Now, a team led by Qian Tang, from the National University of Singapore, investigated where this type of cockroach comes from and how it spread around the world. To do this, analyzed the genetic code of 281 cockroaches from 17 countries on five continents.

From Asia to the world

The study revealed that the German cockroach developed from the Asian cockroach (Blattella asahinai) about 2,100 years ago. Originally, such insects adapted to human settlements in India and Myanmar, according to the researchers.

From there they spread, in the following centuries, to the West, through two routes: about 1,200 years ago, this species took advantage of the economic and military expansion of Islam. And, about 400 years ago, it took advantage of European colonialism, presumably especially British and Dutch.

In human footsteps

Until the beginning of the 18th century, the main area of ​​​​propagation of this cockroach was still limited to Asia, according to scientists in the publication Proceedings, from the American National Academy of Sciences. That changed in the second half of the 18th century, that is, around the time Carl von Linné described the insect.

With the beginning of global trade, the triumphant advance of cockroaches also began, thanks to increasingly faster means of transportation. “The German cockroach then spread to the rest of the world in the late 19th and early 20th centuries,” according to the Singapore study.

Properties and ideal living conditions

Wherever they went, the cockroaches found ideal living conditions in homes with heating and plumbing. In this way, the mortality rate of insects, sensitive to cold, decreased significantly in the coldest regions.

“The advance of human civilization triggered the evolution and propagation of species that adapted to urban environments,” indicated the scientific team.

The only thing that these insects do not tolerate well is dryness. In modern constructions, without wet corners, they do not last long.

There is another additional reason that explains its successful propagation. Compared to other cockroaches, these are especially resistant to insecticides. Those that are resistant to one substance can also become immune to another, over the course of a generation. The genes of the most resistant cockroaches are transmitted to the next generation and, since this insect lives on average about three months, resistance develops with enormous speed.

(ers/ms)

 
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