Note the tibial spurs on the female (arrow pointing at the wasp on upper left). These are used in pushing excavated earth out of the burrow; males have small spurs. Note also the much larger jaws (mandibles) on the female wasp's head (wasp on lower left). These are used to take bites of earth when they are digging a burrow in which to rear their young.
The female shown in the upper left is smaller than average (about 970 mg is an average mass) and the male in the upper right is larger than average (about 425 mg is an average mass); the two wasps in the picture are nearly the same size (approximately 600 mg each) to facilitate comparison.