"The role of an individual in a colony is not always obvious by its appearance. Ants that look similar may be minor workers in one species but queens in another species," study co-author Brian Fisher, an entomologist at the California Academy of Sciences, said in a statement.
For instance, the workers sometimes become queen ants; the queens may have short, nonexistent or large wings; and the queens can often be smaller than the workers. In addition, the genus had three different modes of reproduction, making classification even more difficult.
Mystery solved After collecting and scrutinizing thousands of the ants in Madagascar for two decades, Yoshimura and Fisher figured out a method for distinguishing new species.
It turned out the ants start out as either a male, a large queen or a major or minor worker, Yoshimura said. Though some of the workers may then go on to reproduce or even become queens, identifying the species requires knowing these origin states, not the current role, of the ant. Classifying them also requires understanding their reproductive style.