# Thermal Ecology and Homeostasis in Colonies of the Neotropical Arboricolous Ant Azteca chartifex spiriti (Formicidae: Dolichoderinae)

## TL;DR

This study explores how a tropical tree-dwelling ant species maintains a stable internal environment in its nests despite changing weather conditions.

## Contribution

The research reveals how nest architecture and worker behavior work together to maintain thermal and moisture homeostasis in ant colonies.

## Key findings

- Nest structure buffers internal temperature and moisture against external fluctuations.
- Worker size distribution and activity patterns change with the time of day to meet colony needs.
- Moisture levels are significantly higher at the lower part of the nest.

## Abstract

Ant colonies require a stable internal environment to thrive, yet they must also adapt to daily fluctuations in temperature and humidity. We studied a tropical ant species that constructs large paper-like nests in trees to explore how daily activity, size variations among workers, and nest structure contribute to the colony’s well-being. We measured temperature and moisture levels within several nests and observed worker behavior throughout the day. We found that the nest structure effectively buffered internal conditions against external weather changes, with moisture levels varying from the top to the bottom of the nest. These factors influenced the ants’ distribution and the variation in heat within the structure. Additionally, we found that ants of different sizes were active at distinct times of day, suggesting that workers adjust their roles to meet the colony’s changing needs. This interplay of nest design, internal conditions, and adaptable behavior enables these ants to maintain a safe environment for both brood and adults, helping the colony cope with fluctuating climatic conditions. This understanding enhances our knowledge of how social insects manage environmental challenges and may inspire innovative approaches to sustainable temperature control in human structures.

Arboreal ants occupy a thermally dynamic environment, yet the mechanisms integrating nest architecture and worker behavior to maintain colony homeostasis remain understudied. 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 (27.8 ± 2.41 °C) remained buffered relative to external fluctuations, and moisture was significantly higher at the nest’s lower extremity (p < 0.001). 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, providing essential insights into how dominant canopy ants may cope with future climate change scenarios.