Worse still, when Metz and his co-author Ryan Hechinger H. pumilio When soldiers were sent to “attempt attacks” against other colonies of the same species, the soldiers seemed to back off completely. Scientists are not sure why this would be the case, as the same soldiers are hyper-aggressive when placed near other trematode species, but it suggests that separate colonies of H. pumilio do not compete with each other within the same host.

What’s even scarier is that the two may actually be working together.

This phenomenon is strikingly similar to the way invasive Argentine ants can form supercolonies with millions of queens and billions of workers – and it may provide clues as to how H. pumilio could be so successful.

While scientists have been trying to prove the existence of the soldier caste of trematodes for about 15 years, observing “controversy and disagreement,” parasitologist Robert Poulin of the University of Otago in New Zealand says this new study provides “the clearest evidence yet” that a soldier caste exists, at least in H. pumilio.

“Natural selection has favored division of labor as the best method for maximizing fitness in many colony animals. To date, our best examples come from social insects such as ants, bees and termites,” Poulin says in an email.