The genus Pheidole covers a truly bewildering array of ants — but out of this thousand species, only a handful produce the incredible "supersoldier" ant, a wartime caste marked by an enormous noggin. During times of strife, the supersoldier ants fight in the front lines, and block entries to the nest with their enlarged heads, rendering them a valuable member of the military caste. Yet despite their obvious tactical use, they're only found rarely, and in disparate species of the genus. Is it an example of parallel evolution? Or is there an older link?
Researchers discovered what looked like a supersoldier ant in a wild P. morrisi colony, a species which hadn't been observed with that specific subcaste before. Through analysis of other species that create supersoldiers, they discovered that around 35 to 60 million years ago, an ancestor species developed the potential to create these big-headed fighters. Of the few remaining species that are able to, some maintained the ability throughout the evolution, and some lost the ability to express it, but regained it at a later date.
Even more interesting? This ability lies as a dormant potential, and was able to be induced during soldier development in three different species through the use of hormones. This hints that environmental factors could cause the emergence of the supersoldier caste, but makes us wonder what other abilities are lurking beneath the surface, waiting to return.
Photo by Alex Wild.