Odontomachus haematodus with parasite. Armenia, Belize.

I can’t imagine what an insect infected with a mermithid nematode must feel. In Belize last week we encountered several parasitized trap-jaw ants, each stumbling about with a belly twice the heft of that in a healthy ant. Scaled to human size, a mermithid would be at least as intrusive as an anaconda coiled among the intestines.

Young worms infect ant larvae via contaminated soil in the brood nest. Adult ants who developed with a parasite sapping their nutrients eclose in a recognizably stunted fashion: a swollen, worm-hosting abdomen and a curiously shrunken head. I was surprised on photographing the victims that the trap-jaw could still snap shut audibly and convincingly.

How affected are mermithized ants? Compare an infected individual to a healthy one (albeit of a different species):


Top: a mermithid-carrying Odontomachus haematodus ant with distorted abdomen and shrunken head; bottom: a healthy Odontomachus clarus worker showing typical proportions for an uninfected ant.

When mature, worms break free from their hosts. The process kills the poor ant, but it frees the nematode to mate and lay eggs.

Still. One more reason I’m glad not to be an insect.



photo details:
Canon MP-E 65mm 1-5x macro lens on a Canon EOS 7D
ISO 200, f/13, 1/100 sec
diffused overhead twin flash