Evidence for the Absence of Worker Behavioral Subcastes in the Sociobiologically Primitive Australian Ant Nothomyrmecia macrops Clark (Hymenoptera: Formicidae: Myrmeciinae)

Abstract

Activity in three colonies of the nocturnally foraging Australian ant Nothomyrmecia macrops is investigated. Workers apprehended while foraging were marked, released, and later recaptured within nests following excavation. Every forager in each nest was encountered and marked. It was expected that unmarked, nonforaging, domestic-specialist workers would be discovered in the nests. This was unexpectedly not the case as all workers, apart from one or two in each colony, had been marked, and therefore had foraged at least once during the three-night experiment. The few unmarked individuals are considered to have been temporarily residential nest-entrance guards. Behavioral subcastes comprising “domestic” versus “foraging” workers were thus not indicated, evidencing absence of worker caste polyethism in Nothomyrmecia. The experiment predated emergence in the nests of adult workers from cocoon-enclosed pupae at a season when large feeding larvae of the current annual brood were still being provisioned by foragers. Because Nothomyrmecia is univoltine and emergence of current-brood adults had not yet occurred, all workers present were from preceding annual broods and defined as “postjuvenile.” A previous laboratory study separately evidenced absence of polyethism in Nothomyrmecia. Relevance of the apparent absence of food sharing in N. macrops is discussed.