The island of New Guinea is home to some of the rarest animals on the planet. Among them are over 800 species of ants with a diverse range of fascinating characteristics, each well-suited to their unique island habitat. Scientists estimate that around 60% of these ants are found only in New Guinea. In many cases, a single species originally colonised the island and then developed into multiple distinct forms.
Now two new species of ant have been discovered with the help of a major technique that uses 3D imaging technology to identify insects. The ants themselves have a particularly striking appearance thanks to their formidable spine-covered exoskeletons.
Perhaps just as notable as their appearances, though, are their names, Pheidole viserion and Pheidole drogon, inspired by the fire-breathing dragons from the fantasy series Game of Thrones. While not quite in the same size bracket as their mythical namesakes, the ants do have a strong resemblance to the dragons thanks to the distinct blade-like serrations adorning their backs.
Unlike the dragons of fantasy, however, these ants are a product of evolution. So what is the point of their ornate spines? The answer can be found by looking at the social structure of their colonies. The Pheidole group of ants comprises over 40 species that are widely distributed across the island’s rainforests.
Pheidole ants also have several different types or “castes” of worker, each physically specialised for performing specific tasks within the colony. There are smaller “minor” workers and larger “major” workers, commonly referred to as soldiers due to their role in defending the colony from predators and rival ants.
Not fire-breathing, but still pretty scary. Fischer et al
The spines could be seen as a defence mechanism for the soldiers, but this may not be the full story. Soldiers are often many times the size of minor workers and have disproportionately large heads that are packed with muscle, making them formidable adversaries. Their heads are so large, in fact, that they require special skeletomuscular adaptations just to support their extra weight. Results from a kind of imaging technique known as “X-Ray microtomography” have suggested that the ants' spines are in fact a by-product of this muscular support system, rather than a kind of armour.