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[Vol. 92 
measured by the distribution of sector-numbers pertaining to the 
trips observed. The difference between two successive foraging trips 
is zero if the ant selects the same sector each time (showing perfect 
fidelity), four if she takes opposite sectors, and on average two if she 
selects foraging sectors at random. We obtained records of three or 
more trips for some individuals, but, for simplicity of analysis, only 
used two in our calculations, using the first and the last where 
several data were available for one individual. The mean difference 
for nest 6 was 1.57 (based on seven foragers) and 1.24 (based on 25 
Fig. 1. Furthest points reached by foraging ants from nest 54 during the Sep- 
tember (closed triangle) and November (open square) observation periods. Octagons 
denote active nests, with numbers referring to those given in the relatedness study 
(Crozier et al., 1984). 
