We've heard of animals driven mad by the swarming insects of the Arctic, bedeviled by thousands of biting critters from which there's no escape. There are increasing examples, though, of different ways by which unwelcome guests can drive an animal mad.
A recent study concerns grasshoppers and hairworms. A parasitic hairworm grows inside of the grasshopper's body and, upon becoming sexually mature, has a neat way to insure it'll find other hairworms to mate with: it drives the grasshopper to commit suicide by jumping into water, thus allowing the hairworms to escape from the rear of the drowning insect into the water. Once in the water, they mate with other hairworms that have arrived by the same route. Presumably the next group of grasshoppers becomes infected when they drink larvae-infested water.
How do hairworms control the host? Apparently not by anything so crude as pestering them to death. Instead, they are sophisticated chemists, producing a cocktail of chemicals that affect and control the grasshopper's nervous system. Perhaps the operative term should be "murder by suicide".
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
The prospective victim. Photograph by James C. Leupold, courtesy of the U.S. Fish and Wildlife Service.