Queen body size is associated with method of nest founding across five species of ants in the genus Pogonomyrmex; queens of the largest species do not leave the nest to forage, intermediate sized queens are facultative foragers, and queens of the smallest species are obligate foragers. These interspecific differences in queen foraging result from mass constraints relative to producing their first brood. Whereas queen mass varies >4-fold across these species, the size of minim workers varies by only 0.3-fold. Thus, the cost per minim is similar across species, regardless of queen size. Moreover, to produce their first brood of about 5 minims requires 39% of the initial body mass for small queens compared to 13% for large queens, which leads to the need for small queens to obtain external food sources to rear their first brood.

In addition, environment appears to drive body size in a group of nine ecologically equivalent species of Pogonomyrmex. These nine species display a strong latitudinal gradient in queen body size, with small queen species occurring in cooler northern latitudes whereas large queen species occur in warmer, southern latitudes. Latitudinal variation in method of nest founding is a by-product of this body size gradient, with the two smallest, most northern species having queens that forage to gain resources to rear their first brood, whereas the larger southern species are fully claustral. This system demonstrates how environmental variation can influence differential ways to both obtain and allocate energy resources across a group of closely related species.