The Florida harvester ant Pogonomyrmex badius is the only North American pogo found east of the Mississippi, and the only species that is polymorphic in the worker caste. The individual on the right is a major worker whose enlarged head holds muscles useful for milling seeds. Archbold Biological Station, Florida, USA

Pogonomyrmex badiusPogonomyrmexformicidaemyrmicinaeinsectsantsinsecthymenopterasocial insectscolonycastepolymorphismdivision of labordevelopmentplasticityfemalesant castesharvester antsflorida harvester antgeneticstask partitioninglaborworker typessoldiersmajorsworkerspolymorphic species