File this under "I didn't need to know that."
In a disturbing parallel to human mating practices, female beetles are more likely to mate if the guy offers to buy them a drink. In the current issue of Animal Behaviour (subscription required), Martin Edvardsson has found that female beetles are 40% more likely to mate if they’re thirsty. As reviewed in Science Daily:
Female beetles mate to quench their thirst according to new research by a University of Exeter biologist. The males of some insect species, including certain types of beetles, moths and crickets, produce unusually large ejaculates, which in some cases can account for around 10% of their body weight. The study shows that dehydrated females can accept sexual invitations simply to get hold of the water in the seminal fluid.
So-called “nuptial gifts” are a common tactic by male insects to attract mates. Females of the majority of insects (including the eusocial ants, bees and wasps) mate with multiple males and improve their reproductive success by as much as 70%. As reported in an earlier study in Animal Behaviour (pdf), “the evolutionary maintenance of polyandry in insects can be understood solely in terms of direct effects [i.e. reproductive success].” This has led to sperm competition, a kind of sexual selection, among males in order to improve their chances of fathering some of the eggs. However, in this case we’re witnessing out-of-control sexual selection that puts the peacock’s tail to shame.
Just to put this into perspective (and create a disgusting image that will stick with you all day), 10% of an insect’s body weight would be the human equivalent of filling a 2.4-gallon bucket for your partner’s refreshment.
This isn’t even the most outlandish tale in the annals of insect sexuality. The ejaculate from Drosophila melanogaster (the common fruit fly) is twenty times longer than it’s body length.
Enjoy your lunch!
Drosophila melanogaster after a bit of fun.
Special thanks to Jim for the tip!
Arnqvist, G. & Nilsson, T. (2000). The evolution of polyandry: multiple mating and female fitness in insects. Animal Behaviour 60: 145-164. doi:10.1006/anbe.2000.1446
Edvardsson, M. (2007). Female Callosobruchus maculatus mate when they are thirsty: resource-rich ejaculates as mating effort in a beetle. Animal Behaviour 74(2): 183-188. doi:10.1016/j.anbehav.2006.07.018