1980] 
Stuart & Bell — Leptothorax 
207 
accounts for the weak stridulatory signal, and for the apparent 
absence of any airborne signal (see discussion in Dumortier, 1963). 
Markl and Holldobler (1978) reported that Novomessor workers 
did not transmit any detectable vibratory signal to the substrate 
through their legs. We found this not to be true with L. muscorum 
workers. However, the necessity of having some part of the ant’s 
body, other than its legs, in contact with the substrate, or some 
other object or individual, to facilitate transmission of the signal, 
could be an important communicative constraint in some species. 
Wilson and Fagen (1974) included stridulation in their ethogram 
of L. curvispinosus workers, and apparently observed it as a 
mutually exclusive behavior pattern. In the present study, L. 
muscorum workers only stridulated in association with some other 
behavior. However, in L. curvispinosus colonies cultured under 
similar conditions we have observed workers exhibiting such mutu¬ 
ally exclusive stridulation in apparent response to a mild disturb¬ 
ance, such as moving the culture dish across the stage of a dissecting 
microscope. In addition, L. curvispinosus workers will stndulate in 
many of the contexts outlined in this paper for L. muscorum, but 
only in this ‘mild alarm’ context is this behavior mutually exclusive. 
L. muscorum workers begin to run about their nests, even upon a 
slight disturbance, and we have never observed stridulation in a 
similar context for this species. Free-standing stridulation of this 
type underlines the potential importance of the transmission of a 
stridulatory signal through an ant’s legs to the substrate. 
Our behavioral observations of L. muscorum workers confirm 
and extend previous accounts of stridulation in Leptothoracine 
ants. Adlerz (1896) noted that workers stridulated during trophal- 
laxis, when feeding or licking their nest-mates, and when feeding 
their'larvae. Wheeler (1903) observed workers stridulating while 
feeding on insect fragments, and Haskins and Enzmann (1938) 
reported workers stridulating when licking their larvae. 
The occurrence of stridulation in such a wide variety of contexts 
within a single species, such as L. muscorum, argues against the 
possibility that this signal might release a specific response, and 
supports Markl and Holldobler’s (1978) suggestion that ant stridu¬ 
lation serves a modulatory function. The fact that stridulation is 
observed in additional contexts when colonies have been deprived 
of food and water, suggests that the motivational state of the ants 
may be a factor in stridulation. Zhantiev and Sulkanov (1977) 
