The nesting biology of the scavenger sand wasp, Microbembex monodonta Say, was studied over 2 years (2009 - 2010) in Pedernales Falls State Park, Blanco Co., TX and compared with previous studies. In 2009, nest cell depths averaged 3.4 cm deeper than in 2010, when there was 4 times more rainfall. A total of 177 prey items recovered from 15 excavated nests represented 8 insect orders and the Aranae (Arachnida). In both years, dead alates (nearly all gynes) of the invasive red imported fire ant, Solenopsis invicta Buren, comprised a majority of prey items (62%) and were found in every excavated nest, a most unusual finding. This relatively new and abundant food resource has potential for positively impacting population dynamics of this widespread wasp.