The Love Life of Seed Beetles

There is something about the love life of seed beetles: the female of the species get brutalised when she gets laid, but still she wants more. Seeking to know why this happens, Claudia Ursprung of the University of Toronto Mississauga, put 79 female seed beetles in enclosures for eight days. Some were given solid and liquid food, and others just solid food.

You can guess what happened.

"We wanted to find out whether females were getting food or drinks from the ejaculated fluid," says Ursprung, and her suspicions are now justified: it is the dehydrated beetles that go for sex, reports National Geographic. 

There are two ways of looking at this:

• One is that it is an evolutionary tactic: the seed beetles live in a dry environment- "It is kind of like a bribe for mating, a way of ensuring that the female will produce offspring," according to Darryl Gwynne.
• The other is that since they can't store sperm because of lack of water, they want to get more numbers- "They may be remating for [more] sperm rather than water," according to Karim Vahed.
  

Whatever it is, let me wish you a happy Valentine's Day.

(Watcher, thanks for your comments. Inspired by your remark that this is not mating, I looked up at the love life of seed beetles- now I wish I had not.)

According to Cosmos, the male seed beetles have spectacularly harmful organs covered in sharp spikes, which "look like a medieval torture instrument" (there is a scary photo of it). These help the Male's chances of fertilizing the eggs by providing an anchor, but it causes injury to the private parts of the female beetle. They evolve some padding to protect themselves, but does it help?

Seems it does. The males with more spikes get good anchoring and seed more efficiently. The females with padding survive and produce more offspring, since the less endowed of the species are injured and drop out of the race.

More intimate view of these encounters are at Science News , where we find that a typical act of mating lasts about three minutes. It could extend more, but after three minutes, the female beetle starts to slam her hind legs against the male.

Helen Crudgington and Mike Siva-Jothy of the University of Sheffield in England, who did the experiment, went one up and removed the legs to see how long a male could go on. They got off only after six minutes.

In comparing the damage to the beetles, the longer an encounter lasted, the more rips and tears Siva-Jothy and Crudgington found in the female reproductive tract. And as additional evidence of harm, females that mated only once during the experiment lived longer than females that mated twice.

However tough it is, females of the seed beetles should count themselves lucky when compared with the bedbugs. The male bedbug organ look like a stiletto, and they literally use it as a stiletto- though the female reproductive tracts have external openings, the male bedbugs usually just stab through some spot in the body wall and let the sperm swim from there.


The abstract of the research paper, "Genital damage, kicking and early death" by Helen S. Crudgington and Mike T. Siva-Jothy is here at Nature:

"Because the costs and benefits of polygamy differ for males and females, copulation is not always a cooperative venture between the sexes. Sperm competition can build on this asymmetry, producing male traits that harm females, thereby generating coevolutionary arms races between the sexes. We have found that the male genitalia of the bean weevil Callosobruchus maculatus damage the female genitalia, and that females act to reduce the extent of this damage. We propose that these functionally diametric sexual traits form the basis of reproductive conflict."

What price love?