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Psyche 
[Vol. 88 
two species. It might be expected that the South American species 
would be ecologically similar to P. montanus as they share many 
characteristics (Table 3). 
Production as well as foraging and food input were spread over 
more of the season in P. rugosus than in the other two species (Figs. 
4, 5, 10 & 1 1). This is easily explained as P. rugosus lives in a more 
moderate climate than the other two species. Actually it was 
expected that these processes would occur over the entire year as 
there are many warm sunny days at lower elevations during the 
winter. Yet, activities almost stop. Perhaps these processes do not 
continue as the nest temperatures are lower during the winter than 
they are in the summer (Figure 2). 
The sex ratio was not constant between years (see data in 
Appendix 1). In P. montanus the female:male ratio was 0.88:1 in 
1978, 1.41:1 in 1979, and 0.42:1 in 1980. In 1980 the number of 
males produced was three times those of the other years. An excess 
of females in 1 979 was not found in P. rugosus (0.38: 1 ) as was found 
in P. montanus. An excess of males was found in P. subnitidus 
(0.42:1) in 1980 as was found in P. montanus. 
Nests are extremely heterogeneous in regards to sex ratio 
(Appendix 1). Correlations were investigated between the female: 
male ratio and the apparent age of the nest. Twelve P. montanus 
nests at the peak levels of production were used in the analysis. The 
age of a nest should be related to the numbers of adult workers 
present in the nest and the depth of the nest: older nests should be 
deeper and have a larger worker population. The product-moment 
correlation coefficients (Sokal and Rohlf 1969) of the sex ratio with 
worker population size and nest depths were both 0.17. Although 
the coefficients were not statistically significant, both were positive, 
suggesting that older nests produced greater proportions of females. 
The product-moment correlation coefficient comparing the sex 
ratio with the numbers of workers produced by the nest during the 
year was negative (r = —0.38). Although the relationship was not 
statistically significant, it suggested that nests involved in an 
increase in the worker population (i.e., younger nests) produced a 
smaller proportion of females. Data were presented (MacKay 1981) 
which indicated that food stressed nests produced a greater 
proportion of females; nests given extra food produced a greater 
proportion of males. 
