16 
Psyche 
[March 
Field colonies of A. lorenzo accepted spiders from other colonies 
without any overt sign of aggression. Other unidentified species of 
Theridiidae, when placed in webs, were ignored until they were 
apparently accidentally encountered by resident spiders, at which 
time they were attacked. Other behavioral observations (Table 1) 
were made much the same way as by Brach (1977), and will not be 
further elaborated. Nevertheless, Brach (1977) failed to comment on 
sex ratios. Although field data are few, it is apparent that the sex 
ratios of quasisocial Anelosimus are strongly skewed in favor of 
females. Brach (1975) speculated that the preponderance of females 
was the product of differential cannibalism on males, resulting in the 
female biased quarternary sex ratio. However, data are not available 
on primary and secondary sex ratios for these spiders to ascertain if 
cannibalism is a valid hypothesis. Whatever the cause, female 
dominated populations undoubtedly affect the population genetics 
of these species (Fisher, 1930), and one would expect that females are 
the mobile sex (Cannings and Cruz Orive, 1975), which would tend to 
indicate that inbreeding may be quite high. 
The influence of sex ratio on the population genetics of these 
spiders becomes more evident when the mode of sex determination is 
considered. Although spiders are diploid, sex determination in the 
Araneae is characteristically through a complex system of multiple 
chromosomes, with males being heterogametic (White, 1973). Under 
normal conditions, brothers and sisters within a colony would share 
the same number of genes in common with one another through 
common descent. However, if the female homogametic chromo¬ 
somes have significantly more active gene sites, then sisters would 
share more genes with one another through common descent, than do 
brothers. Thus, at the sex-linked loci, kin-selection (Hamilton, 1972) 
could contribute to the evolution of social behavior in the species of 
Anelosimus in a manner somewhat analogous to the assumed action 
in the Hymenoptera. Undoubtedly, if such a situation does indeed 
occur, morphological and behavioral modifications would to have 
evolved before sociality could be achieved, such as the loss of species- 
specific tactile recognition (Brach, 1977). If indeed quasisocial 
Anetosimus are highly inbred, the possibility that km selection is 
important would be much more probable (Hamilton, 1972). 
Sex ratios dominated strongly in favor of females may also 
inadvertently produce a reproductive division of labor, especially in 
light of the indiscriminate feeding of juveniles by adults. If there are 
