The Way to a Female Katydid's Heart? Offer Her Food [LiveScience 2011-09-27]
[Photo] Two green crickets, Poecilimon laevissimus, mating. CREDIT: Jay McCartney
A tasty gift may be all it takes to lure a female bushcricket into the sack. New research suggests that in bushcricket species in which the males offer particularly large food gifts to a prospective mate, the females are willing to do the chasing.
In most, but not all, species of bushcrickets (also known as katydids), the female searches for a partner, while the male emits mating calls.
Researchers wondered why the gender of the searchers would differ between closely related species. They discovered that in role-reversal species, males lure females into searching them out by producing larger food gifts.
The nuptial gift
The food gift is part of what is called a spermatophore, which contains the sperm and ejaculate encased in an outer, protective covering called the spermatophylax.
The spermatophore provides a source of nutrients for the female and (if the gift is big enough) her offspring too, study researcher Jay McCartney of Massey University in New Zealand told LiveScience in an email.
The researchers studied the males of 32 different species of Poecilimon bushcrickets. The researchers weighed them and studied the size of their spermatophore and its components.
Mates with benefits
In those species with the larger gifts, the females were the searching sex, they found. McCartney believes the female searches more when the males of her species give a large gift because the benefit of the easily obtained food is worth the risk of predation the females face while emitting an attractive call used to seek an available male.
The food gifts themselves are quite costly for the males to produce. "Males that produce small spermatophores can mate twice a night, yet males producing large spermatophores may only mate once or twice in their life," McCartney said. "Adults live and breed for about three weeks, so this can be quite a significant investment."
Luckily for the male, sperm and nutrients aren't the only thing these spermatophores contain. Some research has indicated that they also contain compounds that increase the female's egg-laying frequency and decrease her willingness to mate with other males.
Karin Vahed, a researcher from the University of Derby in the United Kingdom who wasn't involved in the study, isn't sure how beneficial the spermatophore actually is to the female. "Although they do contain protein, they are low in essential amino acids and do not contain the sort of amino acids needed for the female to manufacture eggs," Vahed told LiveScience in an email.
Though modern humans like to think other traits determine whom they select as mates, McCartney said, it's in our evolutionary history to behave the same way as the crickets.
"Nearly all vertebrates have some variation on this; males hold a territory or are the best fighters that hold some resource, etc. Even humans," McCartney said. "Males that are likely to be wealthy or show that they have great resources are always preferred."
The study was published today (Sept 27) in the journal Proceedings of the Royal Society B: Biological Sciences.