The following species of Mutillidae, parasitic wasps commonly known as “velvet ants” or “cow killers” were collected during the period September. 1928, to July, 1930, while the writer was stationed at the Pink Bollworm Laboratory at Presidio, Texas. Presidio County with Brewster County on the east and Jeff Davis County on the north, forms the little known area called the “Big Bend” region of Trans-Pecos Texas.