Thermoregulation strategies in ants in comparison to other social insects, with a focus on Formica rufa

Abstract

Temperature influences every aspect of ant biology, especially metabolic rate, growth and development. Maintenance of high inner nest temperature increases the rate of sexual brood development and thereby increases the colony fitness. Insect societies can achieve better thermoregulation than solitary insects due to the former’s ability to build large and elaborated nests and display complex behaviour. In ants and termites the upper part of the nest, the mound, often works as a solar collector and can also have an efficient ventilation system. Two thermoregulatory strategies could be applied. Firstly the ants use an increased thermal gradient available in the mound for brood relocation. Nurse workers move the brood according to the thermal gradients to ensure the ideal conditions for development. A precise perception of temperature and evolution of temperature preferences are needed to make the correct choices. A second thermoregulatory strategy used by mound nesting ants is keeping a high temperature inside large nests. The unique thermal and insulation properties of the nest material help to maintain stable conditions, which is the case of the Wood ant genus Formica. Ants can regulate thermal loss by moving nest aggregation and alternating nest ventilation. Metabolic heat produced by ant workers or associated micro organisms is an important additional source of heat which helps to maintain thermal homeostasis in the nest.

Sun Basking in Red Wood Ants Formica polyctena (Hymenoptera, Formicidae): Individual Behaviour and Temperature-Dependent Respiration Rates

“…polyctena nests in early spring. We speculate, based on our observations with video thermography and as previously suggested [2–4, 15, 24, 25], that heat transported by sun-basking ants into the nest may contribute to nest heating, together with other internal heat sources like catabolic heat produced by workers and by the nest material, as discussed above.…”

“…polyctena occurred most often in early spring [4, 24]. The total number of sun-basking ants decreased over time in the three replicates of our experiments.…”

“…Wood ants of the genus Formica belong to those social insect species whose colonies are able to keep relatively stable temperatures inside the nest [1–4], as for instance honey bees [5], fungus-growing termites [6], some bumble bees [7], stingless bees [8] and leaf-cutting ants [9]. For the control of climate conditions inside the nest, large nests with good insulation properties are crucial [10].…”

“…Metabolic heat produced by ant workers [3, 11] or by associated microorganisms [12, 13, 14] is supposed to be an important inner source of heat. The level of nest thermoregulation depends on many factors other than size, e.g., population size, moisture and thermal conductivity of the nest material [4]. …”

“…Clustering at the nest surface may contribute to a quick increase of body temperatures of sun-basking ants because workers inside a cluster will have lower thermal losses than single workers [4]. It has been suggested that heat transport by workers returning from the outside, where they exposed themselves to the sun, may work all around the year, even without clustering [2, 17].…”