Mound Temperatures of the Ant Formica Ulkei Emery

Abstract

The temperature characteristics of mound nests of Formica ulkei were compared with those of the undisturbed soil in an attempt to test the hypothesis that one function of mound nest con- struction is the regulation of environmental temperature. The results of temperature measurement were consistent with this hypothesis and indicate that mound temperatures represent a modifica- tion of the temperature regime existing in the soil. Mound tempera- tures differed from those in the soil by being higher, fluctuating season- ally over a wider range, and presenting a wider temperature difference at noon between the depths of 5 cm and 30 cm than exist in the soil at comparable depths over the same period of time. This thermoregulation, which exists during the warmer months only, appears to be a direct consequence of the action of solar radia- tion on the mound structure. However, the possible roles of physio- logical heat production and behavior patterns in regulating mound temperatures are discussed. This report discusses the functional significance of mound nest construction in ants as exemplified by the earthen mounds of Formica ulkei. Previous reports have described the study area, the life history and mound structure of Formica ulkei, and demonstrated that these mound nests maintain a regulated moisture content for the inhabi- tants (Scherba, 1958 and 1959). Do, these mounds also function as a means of regulating'the environmental temperature? The hypothesis that mound nests perform a thermoregulatory