For female field crickets, little is more alluring than the song of a male. But on some islands in Hawaii, the males can no longer produce a noise, despite trying their hardest to do so.
Unfortunately for the males, their love tunes don’t only attract female crickets lured in by their songs, but also female parasitic wasps. These eavesdrop on the calling males in order to inject them with eggs, which eventually develop into larvae and feast on the poor insects from the inside, before bursting out as fully formed adults.
Due to this, the ever-shifting sands of the evolutionary arms race have meant that some crickets have therefore lost the structures on their wings that allow them to make their distinctive calls.
It seems, though, that no one has actually told the male crickets this as despite not actually being able to make any noises, they still sit there ever-hopefully rubbing their wings together, according to a new study published in Biology Letters.
We’re used to talking about vestigial features being something morphological, like the tiny nubs of bone found in the pelvic region of pythons that used to be their back legs, but these male crickets are instead displaying vestigial behavior.
But if the females are attracted to singing males, and the males can no longer sing, then it raises the obvious question of how they now find each other. Well, it seems that not all crickets have gone silent, around 5 percent of males on Kanuai and half of the males on Oahu can still trill a tune.
“It appears that [the silent ones] hang around singing males and intercept females that come in,” Dr Nathan Bailey, co-author of the latest study, told The Guardian. “In effect, they parasitise the songs of the singing males. It’s a bit sneaky.”
It's unlikely this is the full picture, though. Considering that such a high proportion of males on Kanuai can no longer sing, it seems unlikely that they are all piggybacking on the few remaining vocal ones. It suggests that they have come across another way to attract the females, although no one is quite sure what this might be.
Interestingly, these crickets are not alone as animals that have vestigial behavior when it comes to finding love. The adorable pumpkin toadlet continues to call his little song even though the jazzy amphibians are completely deaf.
This seems particularly odd, but the researchers think that perhaps the inflating of the throat and gaping of the mouth might be a visual signal and the noise is simply a by-product. Similarly, the team looking at the crickets will now look to see if the silent male insects stopped singing altogether to save energy, or if moving their wings serves some other function.
[H/T: The Guardian]