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Psyche 
[Vol. 87 
report variations in the stridulatory signal of Myrmica which they 
suggest could reflect the relative motivation of the signalling 
worker. If so, stridulation could constitute a finely graded signal 
which serves as a sensitive indicator of the relative motivational 
state of workers engaged in various social interactions with nest- 
mates. In this manner, stridulation would be an important contri¬ 
bution to the efficiency of these interactions and of the colony as a 
whole. Stridulation could simultaneously serve as an effective short- 
range recruitment signal or orientation cue, especially within the 
nest. Outside the nest, L. muscorum workers recruit nest-mates by 
tandem running to food (Moglich et al., 1974) and to fighting 
(Stuart, 1978). The occurrence of stridulation at the scene of either 
of these activities could serve to facilitate such chemical recruitment, 
as it has been shown to do for food recruitment in Novomessor 
(Markl and Holldobler, 1978). However, these suggested functions 
for stridulation in L. muscorum remain speculative, and the precise 
determination of the effects of this signal, in the various contexts 
described in this study, await further research. 
Acknowledgements 
We thank E. Lin and B. Moose of the Laboratory of Analytical 
Systematics in the Department of Zoology, University of Toronto, 
for their electron microscopy. We appreciate financial support from 
an Ontario Graduate Scholarship, a NSERC Postgraduate Scholar¬ 
ship, and N.R.C. (Canada) Grants #A0301 and #4946 to R.S., P.B., 
and Drs. T.M. Alloway and G.K. Morris respectively. 
Summary 
L. muscorum workers possess a stridulatory apparatus on the 
dorsal surface of the third and fourth abdominal tergites. Stridula¬ 
tion is readily induced by gluing the ventral portion of a worker’s 
head directly to the accelerometer. Under these conditions, a 
vibratory signal with an acceleration of 1.4 X 10 4 m/sec 2 RMS is 
recorded from the substrate. However, no sound is detected by a 
microphone held to within 1 cm of the stridulating ant. A similar 
vibratory signal is recorded from the substrate when a worker is 
restrained by having an antenna clamped in forceps such that the 
ant is free-standing on the accelerometer surface. This proves that 
