Suicide bombing. Horrific. Unnatural. A special kind of human horror. And... part of the natural world.
While most of the discussion of suicide bombing in the press focuses on it as an inexplicable part of the human experience, one of those nasty human practices that sets us apart from the rest of the animal kingdom, a new paper in Science (pay-walled) discusses altruistic suicide bombing in Neocapritermes taracua, a termite species found in French Guiana, France's territory wedged between Suriname and Brazil.
The paper begins with a quote from EO Wilson's and Bert Hölldobler's 1990 masterwork The Ants -- "we send our young men to war... ants send their old ladies" -- a reference to the long understood tendency of many eusocial insects (all ants and many wasps and bees) to assign older members of the colony the most dangerous tasks.
In the case of these termites, some members develop the ability to become suicide bombers for their colony in times of danger as they grow older. As the termite workers age, the mandibles they use for work (chewing up wood) wear out, making them less effective at foraging. These older workers develop a pouch filled with a blue toxin (the color caused by the presence of copper). The older they get, the bigger the pouch.
"As the feeding efficiency of workers decreases, they build up their backpacks for suicidal fighting," the authors write. "Blue workers were more aggressive than white workers toward other soil-feeding termites... and they burst sooner after being seized by their opponents. Bursting liquid from blue workers was more effective than liquid from white workers."
Adding to the toxicity for the suicidal termites is the location of the pouch with the blue fluid near their salivary glands. The mixing of the termite's saliva and the poison makes it more potent, the authors found.