Cockroaches: discover why it is so difficult to fight them

Cockroaches are changing their sex life and it's all our fault.

When confronted with a poisoned sweet bait, the roaches first had a mutation that made them hate sweets, making their mating strategies difficult.

Now,

, proving that you can't control a good pest.

Like many animals, cockroaches have a sweet tooth, and that preference for sugar plays a central role in their reproductive activities.

When a male cockroach wants to mate with a female cockroach, he backs off toward her, secreting a solution called the nuptial gift from the tergal gland located under the wings.

The solution is full of protein, fat and sugar.

The female roach climbs on his back to take a sample, and while she is busy, the male pulls out a hooked penis to mate with her reproductive tract.

They then turn back to back and mate for

.

Humans have tried to exploit that love of sweet things

.

For decades, glucose-containing poison baits were used.

The cockroaches

.

But sometime in the late 20th century, a new mutation emerged:

.

No one knows how many cockroaches now hate sweet things, but Coby Schal, an evolutionary biologist at North Carolina State University, suspects that the mutation is very common.

“More and more articles are being published about the fact that a whole series of baits

,” he said.

A whole series of baits no longer works so well.

This lack of sweet tooth saved the roaches from death, but

.

The gift secreted by normal males contains maltose, a sugar that cockroach saliva converts to glucose.

But if females have the glucose aversion mutation, the male secretions are unattractive to them and

before the male can mate.

But Schal and his colleagues noticed that glucose-averse males were still having luck with glucose-averse females.

They studied this extensively, comparing the mating between the sweet-loving roaches and the sugar-free variety.

In a study published Wednesday in the Proceedings of the Royal Society B, scientists show that

.

Instead of producing wedding gifts with more maltose, they produce ones that contain a more complex sugar, maltotriose.

That substance takes longer to break down into glucose in a female cockroach's saliva, Schal said, and "it's actually preferred by females."

But even with a sweeter treat, glucose-averse roaches weren't taking chances.

Sugar-loving males took

to start mating with a female while she was eating dinner, Schal said, which meant they only succeeded half the time.

The sugarless males went into action in

, successfully 60% of the time.

Marlene Zuk, an evolutionary biologist at the University of Minnesota Twin Cities who was not involved in the study, praised it, saying it was interesting for "people who don't deal with cockroaches as such" and that it revealed facets of how behaviors evolve. of mating.

“It exemplifies very well that there is a constant balance” between survival pressures and the pressure to mate as much as possible, he noted.

But the latest mutations arose among laboratory-bred cockroaches, said Richard ffrench-Constant, who studies insect molecular biology at the University of Exeter in England.

"Whether these are the traits that are actually going to emerge in nature, I think is debatable," said ffrench-Constant, who was not involved in the study.

Zuk added that these mutations did not arise on purpose.

Glucose aversion solved one problem and he created another, but male roaches weren't going around trying to make sweeter wedding gifts.

For every mutation that helps one cockroach get lucky, another might do the opposite.

“Things just happen,” he said.

"There's no guarantee that you're going to succeed in any way."

But this time, the cockroaches' romance emerged victorious.

The New York Times.

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