We observed aggregations of the sand wasp, Steniolia nigripes, in the Granite Mountains of Southern California. Males gathered in open areas between bushes in a sun-dancing behavior very close to the ground. They did not hold exclusive territories. Aggregations were highly visible, but occurred at low densities in the area. Males often chased each other and females, who would approach the aggregation, then leave with males following closely or attached to her. Females often burrowed around the edges of the aggregation. We captured and measured male and female head width, dry weight and thorax length. Males were significantly larger than females in all of these measurements. Intrasexual selection resulting from scramble competition for access to mates may drive this dimorphism. As these aggregations did not occur at obvious landmarks, it is possible that the aggregations themselves serve as a landmarks for females.

Ants exhibit a size-associated colony founding trait that is characterized by the degree to which foundresses rely on internal reserves to raise their first brood of workers (claustrality). The reliance on stored reserves is positively correlated with degree of claustrality (claustral > facultative > semi-claustral) and is variable across species of Pogonomyrmex harvester ants. Three species of harvester ant foundresses that differ in degree of claustrality were observed initiating nests under laboratory conditions over 2 years. P. rugosus is fully claustral, P. salinus is facultative, and P. californicus is semi-claustral. Across species, degree of claustrality was positively associated with mean digging rate and nest depth over the first 3 days of nest initiation, total nest depth, and degree of nest closure. Branching and abundance of peripheral nodes were higher in semi-claustral and facultative nests than in claustral nests. The facultative species dug for the longest time and achieved the greatest tunnel length. Within each species, there were trends associating mass with digging rate, but these were not consistent in all species. There were no intraspecific trends of mass with nest depth. Also within species, a foundress’s mass did not affect her tendency to open or close her nest. These results reveal degree of claustrality is correlated across species with several nest initiation characteristics that together may represent different colony founding syndromes.