Differential viability of eggs laid by queens in polygyne colonies of the fire ant, Solenopsis invicta

Abstract

The viability of eggs laid by individual functional queens from polygyne colonies of the fire ant, Solenopsis invicta Buren, was examined by staining for chromatin. In isolation units held in the laboratory inseminated queens laid nearly 100% viable eggs, compared to <10% for uninseminated queens. Experiments in which the quantity of brood was manipulated demonstrated that the number of brood and workers present has little, if any, effect on the ability of a queen's eggs to form embryos, in contrast to the stimulatory effect of larvae on oviposition rate. In field colonies, although there was considerable variability among queens, inseminated queens laid a significantly greater proportion of viable eggs than did uninseminated queens. Inseminated queens taken directly from polygyne colonies in the field laid a smaller proportion of viable eggs than those maintained individually for several weeks in the laboratory, suggesting that there is mutual inhibition among cohabiting inseminated queens which affects viable egg production. Among queens taken from the field, there was no significant correlation between the proportion of viable eggs laid and queen weight, a reliable indicator of oviposition rate. Thus caution should be exercised in equating relative rates of egg production with reproductive success in studies of reproductive roles in social insect colonies.