Bedbug Reproduction and Traumatic Insemination

Pity the poor female bedbug – she does not have any genitalia. So how do bedbugs reproduce? Through the bizarre act of traumatic insemination.

Bedbugs (also spelled bed bugs) such as Cimex lectularius reproduce in a way much different than other animals – even other insects.  This process is very accurately called traumatic insemination.  However, researchers Alastair D. Stutt and Michael T. Siva-Jothy report that in their observations of 89 traumatic inseminations, the female never once resisted a male.

The Process

The male has a blood meal. 36 hours later, he’s ready for copulation.  The male locates a female based on size.  Females are often larger than males, but a male trying to copulate with other males does happen in the bedbug world.  Upon finding a female, the male locates a groove in the female’s abdominal wall, stabs through her exoskeleton with his sexual intromittant organ. Once skewered, the male pumps in semen, withdraws and crawls off to find another blood meal.

Underneath the punctured exoskeleton, the male’s sperm enters the female’s mesospermalege.  This is a pair of fake sexual organs modified from the insect’s immune system.  The theory is that males used to stab a female anywhere and injected sperm into the bloodstream, as happened to the closely related bat bugs. But if the male is going to stab, he should just stab in one place most able to take the blow.  So the female’s body evolved just such a location. Inside are spongy tissues and a liquid called hemolymph.  The sperm rides the hemolymph to the female’s ovaries.

The sperm finally combine with the eggs. She lays about six per week and can lay up to 500 in her one year lifetime if she is able to get a hold of blood meals about every two weeks.

Complications

Bedbugs, although not a social species like termites or bees, do cluster together in hiding places.  Female bedbugs, after several traumatic inseminations with males, often crawl off alone to recover, according to Cornell University.  If she is inseminated too many times, she can develop an internal infection and die.  According to Stutt and Siva-Jothy, bedbug females receive an average 20 traumatic inseminations per month.

But by crawling off to get some peace and quiet, she also winds up spreading the bedbug population throughout the general area.  This helps more bedbugs find more sources to feed from so that more and more and more bedbugs do not feed from the same body or bodies.

Another complication is that the sperm from the first male that inseminated her will not succeed in fertilizing her eggs.  That honor goes to the sperm from the last male that inseminated her.  Just how this happens is unclear.  It could be that the female’s mesospermaledge chooses which sperm will live and which will die.  This may be why it is so closely tied into the female’s immune system. Should this theory prove to be true, then perhaps the female bedbug has the last laugh after all.

Sources

Cornell University New York Integrated Pest Management. “FAQ List for Bed Bugs.” http://www.nysipm.cornell.edu/whats_bugging_you/bed_bugs/bedbugs_faqs.asp

“Traumatic insemination and sexual conflict in the bed bug Cimex lectularis.” Alastair D. Stutt and Michael T. Siva-Jothy. “Proceedings of the National Academy of Sciences of the United States of America.” Vol 108, No. 13. March 29, 2011. http://www.pnas.org/content/98/10/5683.full

National Geographic News: “Bat Bugs Evolved Fake Genitals to Avoid Sex Injuries.” Anne Minard. Sept. 25, 2007. http://news.nationalgeographic.com/news/2007/09/070925-bat-bugs.html

Image by Rickard Ingell for Wikimedia Commons