Female beetles have a thirst for sex
- Female beetles have a thirst for sex
- 06 June 2007
- NewScientist.com news service
Buying a lady a drink to win her favour is a trick not confined to men. Some beetle females will mate simply to quench their thirst.
The bean weevil Callosobruchus maculatus feeds on dry pulses. With a diet like this, the male's ejaculate is a valuable water source for females. Martin Edvardsson at Uppsala University, Sweden, tested the idea that females tap into this by keeping them on dry beans with or without access to water. Females living on beans alone accepted more matings, presumably to secure the water in the seminal fluid (Animal Behaviour, DOI: 10.1016/j.anbehav.2006.07.018).
Edvardsson says that the energy used to produce the ejaculate, which makes up a whopping 10 per cent of a male's weight, is well spent. Once impregnated, females lose interest in sex - probably to avoid further injury from the male's spiny penis. They are more likely to mate again if they are thirsty. "This is a massive investment for the male," Edvardsson says. "It buys them time before the females remate and their sperm have to compete with that of other males."
Females with access to water lived on average for a day and a half longer than those without water. Since average lifespan is only around nine days, this makes quite a difference to the total number of eggs they can lay.From issue 2606 of New Scientist magazine, 06 June 2007, page 20