You stink to me
"Anyone who sleeps with the same person twice is already part of the establishment", this slogan is taken to heart by the female short-winged cricket. But how does she know which male she has had the pleasure of?
Ms. Cricket is not very choosy: when she is in the mood, she goes out and looks for a willing man. First of all, she lets herself be charmed – so much time must be allowed; without a male courtship song, the female short-winged cricket (Gryllodes sigillatus) does nothing. After the sweet hour she moves away and is immediately looking for the next partner.
Scientists assume that the reason for this behavior is a genetic advantage through diversity: if a cricket catches a male with bad or unsuitable genes, it can compensate for this disadvantage - because the children that hatch at the same time are by no means all fathered by the same father. If she mates with several, it can be expected that she will meet a top father for at least some of her offspring. Even incest is then no longer an issue, because should she ever get caught up in her own brother, she can get over this incestuous misstep in view of the large number of descendants from other fathers.
But what happens when Miss Cricket comes across the same man twice? Mating with him again would bring no genetic advantage. And since sex involves effort and also carries the risk of falling victim to a predator, the cricket should avoid repeating the sweetheart's lesson as much as possible. What she actually does, as Tracie Ivy found out with her colleagues at Illinois State University. The researchers brought females together with a partner and let nature take its course. After mating, they separated the two for 24 hours. Then they presented the lover of the previous night to the female, as well as a male she had never known before.
Now the scientists sat next to their test animals and waited for both males to chirp. If someone remained silent, they had to cancel the round as invalid, as it robbed them of all chances from the start. Then Ivy and her colleagues waited for the choice of crickets - and lo and behold: Ms. Cricket usually preferred the unknown.
But how can an insect, whose intellect even you inclined researchers consider rather limited, know which male it has had close contact with before? The scientists assumed that scents serve as signal transmitters. Time for a second experiment: First, they bred groups of genetically identical crickets that also produce the same scents. Then, as usual, they let their female experimental crickets have a romp with an unrelated male.
The next day, each female again had a rendezvous with two suitors, whereby the researchers selected them according to certain criteria: In one test group, one of the males was a twin of the lover from the previous day. If female crickets were to remember the smell of their lovers, they would have to despise their brothers, who smell the same, as often as they do themselves. Apparently, however, the crickets did not recognize the smell, but were just as likely to mate with the relatives of their discarded lovers as with strangers.
In the second group, one of the two admirers had had fun with the cricket's twin sister the day before. The researchers suspected that if the cricket used the scent trail it left behind during the act of love, it would now have to despise the male on which the sister who smells the same has left her markers. And indeed: The crickets chose the male significantly more often, which in the past had only had fun outside of the female's family.
The great advantage of this strategy is that the cricket doesn't have to use its memory. She just sniffs the cricket man and compares his scent with her own – after all, she always carries it with her. Biologists describe this form of recognition by comparing one's own scents with an odor trail as the armpit effect.
For the men there is only one moral of the story if they want to please their beloved several times: Always shower thoroughly after sex!