The male cockroach (right) secretes a solution that attracts the female (left), and the female climbs on the male’s back and drinks the solution. Provided by Ayako Wada-Katsumata
When a male cockroach finds a female he likes, he prepares a sweet gift. This is to lure females with gifts. However, it is said that the taste of gifts has changed recently.
Sweetness is an important key to cockroach reproduction. Male cockroaches secrete a sweet liquid from glands under their wings and slowly approach the female. The female cockroach climbs on the male’s back to drink the solution. This is the moment when cockroach love begins.
Pest control companies have been taking advantage of cockroaches’ tastes to create repellent drugs by mixing poison with sweet glucose to attract cockroaches. However, last March, Professor Cobie Scall’s team at the University of North Carolina published research results showing that German cockroaches changed the way they make love by adapting to drugs administered by humans.
The research team analyzed the courtship behavior of males that dislike glucose and males that love glucose. As a result, they discovered that males that hate glucose have a genetic mutation that allows them to secrete a complex sugar called maltotriose.
Traditionally, males secrete a solution containing maltose, and the maltose is broken down into glucose the moment it touches the female’s saliva. On the other hand, maltotriose is not broken down into glucose when it comes in contact with saliva. So even females that dislike glucose can continue mating without avoiding males.
The research team analyzed that the new generation of cockroaches felt the bitter taste of glucose so strongly that they avoided glucose. Cockroaches that like glucose die after taking the repellent, while those that hate glucose survive, and the mating strategy of the cockroaches gradually changes.
Professor Cobie Scal said, “Animals develop a sense of taste to sense the bitter taste of poisonous substances in order to protect themselves,” and added, “Cockroaches are the first to evolve to avoid glucose, a universal energy source for living things.”
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