The size of queens influences their ability to found a colony successfully.  We videotape queens in the process of digging burrows, digitize size from the video images, and monitor survival.  We have found that larger queens survive better than smaller queens.  Head size and thorax size are highly related to survival probability (although gaster size is not).  In the graph below notice that surviving queens (connected with solid lines) have larger head width than the dying queens (dotted lines).  Virtually all of the selection on queens comes during the first two-three weeks, with no perceptible further change after two and a half months.  

A queen digging the first nest burrow  Head width changes rapidly