The specialization or production of one sex of reproductives was common among individual colonies of southern fire ant, Solenopsis xyloni (McCook), at Naval Air Station, North Island in San Diego, CA. However, the overall sex ratio of all the colonies was 1:1. We examined the sex ratios among alates of S. xyloni to determine if the production of alates followed the predictions of Trivers and Hare for investment ratio in a polygynous species (male bias). Seven colonies were male biased, 8 were female biased, and 2 had a 1:1 male to female ratio. The population investment sex ratio for all the colonies at the San Diego site was 1:3 (male to female) by fat and dry weight contrary to expected male biased investment proposed for polygynous species.