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RESEARCH PRODUCT

Nest modifications by the acorn ant Temnothorax crassispinus (Hymenoptera: Formicidae)

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Many ant species construct nests and during the process considerably influence the environment such as by changing soil structure and creating new habitat for other species. However, other ant species dwell in ready-for-use cavities. Ants of the genus Temnothorax inhabit small cavities such as acorns and under rocks, but under natural conditions, good nest sites are limited resources. During field and laboratory experiments, I studied how the acorn ant Temnothorax crassispinus (Karawajew, 1926) modifies nesting sites. Temnothorax crassispinus is a forest species, which typically lives in cavities in fallen twigs and acorns; colonies usually number from a few dozen to about 200 workers. Although it is known that they prefer narrow entrances, in a field experiment, a similar proportion of artificial nest sites with narrower and wider entrances were inhabited, and most colonies decreased entrance sizes. Similarly, in laboratory experiments, colonies decreased entrance sizes. Colonies used more sand grains when sand was placed closer to the nest entrance than when it was farther; however, I found no relationship between the number of grains of sand used for such modifications and colony size, and the presence of other colonies in the same Petri dishes did not affect entrance-size reduction. Other experiments showed that the ants can enlarge the nest cavity, but this depends on the material filling the cavity, and that the ants are able to dig nest chambers just in soil. Thus, acorn ants can modify and create nest sites, and may thus also modify the environment.