Harvester ants are recognized by their:

Harvester ants are distinguished by their specific physical characteristics which include having two nodes on their pedicel. This feature is a key identifying trait of this species, setting them apart from other types of ants. Additionally, harvester ants are typically characterized by their red or black coloration, but the presence of two nodes is what properly aligns with the definition of harvester ants within the scope of entomological taxonomy.

The other details presented in the other choices do not accurately match the defining features of harvester ants. The ability to mimic other ant species does not apply to them specifically; their coloration is relevant, but not in the context of having two nodes. Finally, while some ant species may have notable variations in head-to-body size ratios, this is not a defining characteristic of harvester ants. Recognizing these specific traits is essential for effective identification and understanding of the species in pest control contexts.