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Abstract

The behavior of ants digging through sand or clay in the direction of trapped nestmates has been described by Belt (1874) and Lafleur (I940). Wilson (1958) showed that in Pogonomyrmex badius (Latreille) this behavior pattern is released by a volatile substance originating from the mandibular glands. Later, McGurk et al. (1966) identified the responsible compound as 4-methyl-3-heptanone. At the same time, Blum and Warter (1966) isolated 2-heptanone from Conomyrma pyramica (Roger) and described its function as the releaser of alarm and digging behavior. Spangler (1968) reported that not only whole workers, but also amputated parts as well as larvae and pupae of Pogonomyrmex occidentalis (Cresson) attract workers of this species and release digging behavior. Forrest (1963) studied Lasius flavus nearcticus and four species of Acanthomyops and found that workers also dig to free ants of another species but attack them as soon as they are released.

During studies on a colony of Solenopsis geminata (Fabricius), I noticed that returning foragers started to remove a plug of cotton used to block the entrance of an artificial nest immediately after its mounting, even if the position of the entrance was rotated through 180°. During most of these actions, they used their mandibles to chew away small pieces of the obstacle. The purpose of the present paper is to report on the finding that this behavior is released by the carbon dioxide produced by the ants trapped inside the nest.