Trying to bait cockroaches with sweet compositions, trap makers could not assume the consequences that this would lead to the reproductive strategies of the critter.
Thirty years ago a study in the journal Science announced the appearance of a line of German cockroach having developed an aversion to glucose. Small in size, Blattella germanica, the most common species of cockroaches, nests in kitchens around the world.
The pitfalls to eliminate it have long worked by using its appetite for glucose, which comes to coat a deadly substance. Some insects have adapted by avoiding them.
But their aversion to sugar had an impact, as the substance was initially as important for food as it was for reproduction, notes the study published in the journal Proceedings B of the British Royal Society.
The male cockroach has a very particular tactic to curry favor with a female. It spreads its wings, secreting with a gland a nuptial juice based on maltose, a form of sugar. The female comes to taste it by climbing on her back, which then gives the male time to connect his genitals to that of his partner.
Females who have developed an aversion to sugar, to better avoid death traps, have also shortened their antics with males.
Until male cockroaches sharing this aversion find the parade, as explained in the study conducted by Ayako Katsumata, a researcher at the Urban Entomology Laboratory of the American University of Raleigh, a pioneer in this field.
The male cockroach has developed two techniques to achieve its ends.
It has changed the composition of its nuptial secretion, which contains five times less glucose than that of an average cockroach, and especially two and a half times more maltotriose. This kind of sugar has a double advantage. It is very tasted by females, and converts more slowly than maltose into glucose under the effect of the female's saliva.
Second display, the male cockroach takes action on average in 2.2 seconds, almost twice as fast as the average cockroach. Not giving the female time to convert some of her juice into glucose, and thus shortening the foreplay.
To the point that the big loser of the case is now the average male cockroach, who strives to produce a juice too rich in glucose, and who delays in concluding, is sent back into the ropes by the female when she realizes it.
The authors of the study stress that it is important to understand how the sugar aversion trait spreads in the cockroach population, if manufacturers want to develop effective insect control strategies.
© 2023 AFP