Effects of Temperature on the Surface Activity of the Desert Leaf-cutter Ant, Acromyrmex versicolor Versicolor (Pergande) (Hymenoptera: Formicidae)

Abstract

Field studies were conducted from 30 June-10 Dec. 1973 on 4 colonies of A. v. versicolor near Tempe, Arizona [USA]. Soil surface temperatures and corresponding ant activity were recorded. A. v. versicolor was active above ground at surface temperatures between 7.7.degree.-44.degree. C. The ants were primarily nocturnal during the hot summer months but shifted toward diurnal activity as autumn progressed. Between 30 June and 14 Nov. 1973 the ants engaged in a daily activity cycle that was initiated and stopped by the normal daily temperature variations. During this period the ants used the maximum amount of time when temperatures were tolerable for surface activity. When A. v. versicolor workers are stranded from their nest and subjected to high air temperatures, they press their bodies against the cooler surface, allowing conduction of body heat to the soil and possibly permitting survival during short periods of high temperature.