WWW: Cockroach Zombies and Their Wasp Masters
Weird Wildlife Wednesday: Halloween Edition continues with an episode of Radiolab about parasites that completely creeped me out.
I have to say that despite a very honest effort on my part to like insects and the writing of awesome entomologists like Gwen Pearson, that I cannot bring myself to like cockroaches. In addition to this I’m also a bit trypophobic which made this particular animal interaction give me the heebie-jeebies.
It all starts with the jewel wasp, also known as the emerald cockroach wasp.
A female jewel wasp mates only once in her lifetime, but carries dozens of eggs which she then each incubates in its individual cockroach host.
This wasp lands on a cockroach and stings its brain in very precise locations as it injects mind-controlling venom. After the roach becomes submissive, the wasp brings it to a chamber where it lays an egg on the back of the roach, sealing it in with pebbles. Once hatched, the larvae eats its way into the roach to feed off its roach guts, eventually killing it and emerging once it has developed enough.
The precision of the brain sticks are remarkable- the wasp first knocks the roach on its back and stings the underbelly of the roach, paralyzing the front legs. Paralysis causes the roach to struggle less, allowing the wasp to then sting in the neck for roughly a minute, at which point the wasp actually steers its stinger through the tissues in the roach head until it makes contact with the brain. Special sensors on the stinger facilitate this process as the wasp leaves venom in two locations, the ganglion and sub-esophageal ganglion.
After the roach is stung it will groom itself for about thirty minutes, giving the wasp enough time to locate a confined space for her victim. Once the cockroach stops grooming it will remain still and not move without prompting from the wasp who then amputates the roach antennae and drinks the hymolymph from inside, using the nutrients to replenish that lost in the struggle.
The wasp then leads the cockroach to the burrow and shoves it inside for the egg laying. Two days later, the egg hatches and begins consuming the roach organs. After the roach mercifully dies, I actually do feel quite sorry for it, the larvae lines the inside of the roach-corpse with antimicrobial goo and pupates inside the corpse for a month before it merges as an adult wasp.
To see an image of the wasp emerging from the roach, taken by Ram Gal, click here– but I warn you, it is really gross.
The source article for this post was written by Matt Simon for Wired is a really interesting read.