Competition Produces Giant(er) Noggins

big-headed-antI have a large head. When I first started playing peewee football, they had to grab me a helmet from the varsity team. Once I got to junior high, they had to run over to the high school to find my head some protection. Hats don’t usually fit.

I look like an orange on a toothpick.

But I’ve got nothing on the big-headed ant, which, yes, is an actual species of ant. You’ve probably seen one as they live just about everywhere on the globe. Since their giant, Schwarzenegger-like noggins give their pincers incredible strength, they tend to take over new communities when transplanted by human activity.

That’s right, they’re an invasive species bent on world domination through their pincers.

Since the big-headed ant lives in so many regions in the world, researchers from the University of Illinois thought it might be an interesting opportunity to study how local conditions affect ant populations. More specifically, they thought that big-headed soldier ants might be larger or more numerous in areas with dangerous foes.

For example, Australia has numerous species of fierce and competitive ants that while Hawaii has zilch. And because workers and soldiers are developed through feeding versus genetics, as are their counterparts in bee colonies and other social insects, the community has direct control over their growth.

So perhaps the colony might start feeding their offspring more “soldier jelly” earlier in their development if there’s a lot of danger around. Or maybe they’ll turn more larvae into soldiers than workers.

As it turns out, the former is the way they roll.

antmapAlthough colonies in Australia and other areas of high competition don’t create more soldiers than their cousins living the easy life in Hawaii, they do make bigger soldiers. On average, the researchers found that soldier ants in Australia are three times bigger than those in Hawaii.

They also looked at three sites with intermediate levels of competition in Florida, Mauritius, and South Africa. And sure enough, the size of the soldiers all fell within the two extremes found in Australia and Hawaii.

The researchers hypothesize that the ants use chemical signals called pheromones to determine when the nest has the right proportion of soldiers to other workers. If this turns out to be the case, scientists may be able to control the ants with chemical signals without disrupting the surrounding ecology.

The study, “Body size variation and caste ratios in geographically distinct populations of the invasive big-headed ant, Pheidole megacephala (Hymenoptera: Formicidae),” was published in the Biological Journal of the Linnean Society by University of Illinois entomology professor and animal biology department head Andrew Suarez, along with postdoctoral researcher Bill Wills.

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About bigkingken

A science writer dedicated to proving that the Big Ten - or the Committee on Institutional Cooperation, if you will - is more than athletics.
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