Thermal Ecology and Homeostasis in Colonies of the Neotropical Arboricolous Ant <em>Azteca chartifex spiriti </em>(Formicidae: Dolichoderinae)

The circadian rhythm regulates the activity of the ants according to environmental conditions. We investigated the interplay among circadian rhythm, nest homeostasis, and worker morphology in Azteca chartifex spiriti, a Neotropical arboreal species that builds large polydomous nests suspended in trees. In ten colonies, we measured internal moisture and temperature gradients in the main nest, which houses most individuals, including the reproductive female, immatures, and numerous workers. In six colonies, we assessed the polymorphism of foraging workers over a 24-h cycle in relation to external temperature variation. The results show integrated thermoregulatory mechanisms that combine passive strategies, derived from nest architecture and moisture gradients from the suspension base to the lower extremity, with active strategies linked to foraging patterns and worker polymorphism. Internal temperature remained stable despite external fluctuations, and the humidity gradient accounted for both internal population distribution and heat absorption or release. Worker size displayed a bimodal distribution during the day that shifted to a unimodal pattern at night, indicating behavioral adjustments to thermal and operational demands. These findings demonstrate that the interaction between physical structure and worker behavior maintains colony homeostasis and enhances the ability of A. chartifex spiriti to persist in environments with fluctuating climatic conditions.