Density of colonies together with size and spatial distribution of foraging territories of the subterranean termite,Heterotermes aureus(Snyder), were determined on a 1600-m2bait sampling grid in a shrub-invaded desert grassland on the Santa Rita Experimental Range S of Tucson, Arizona. Bait units (toilet paper rolls) attacked on the first wk of the 52-wk study and those with large, mean weekly forager counts were considered as colony foci. Lateral spread of colony boundaries was followed weekly. After one yearH. aureushad attacked 22.8% of the bait units. Colony density was estimated at 190A/ha, mean territory contained 12.5 m2and mean number of individuals/colony was speculated to be 22,632.