Queen/worker thorax volume ratios and nest-founding strategies in ants

Queen/worker thorax volume ratios were calculated in nine monogynous, seven polygynous and eight parasitic ant species in order to determine whether mode of nest founding is reflected in relative gyne size. A significant difference in this ratio was found between monogynous (independent nest founders) and polygynous and parasitic species (dependent nest founders). Thorax volume ratio in ants appears to be independent of actual gyne or worker size and can be used as a relative measure of colony investment in the gynes. Furthermore, thorax volume ratio seems to reflect the mode of nest-founding behaviour when compared between species within genera as well as among species in general. Polygyny is discussed as a nest-founding strategy that is selected for when nest founding by single gynes is difficult and costly. In addition, secondary benefits could be gained by polygynous colonies since investment in gyne size could be decreased.