The male and female of Chilicola (Chilicola) venticola, Packer, new species are described based upon material from Santa Cruz Province in Patagonian Argentina. The previously unknown females of C. (Chilioediscelis) araucana Toro and Moldenke and Chilimelissa australis Toro and Moldenke are also described. Notes on the nesting biology and adult behaviour of the species are given. Chilimelissa australis is the second xeromelissine known to nest in the ground and the possibility that other congeners nest in similar substrates is discussed. SEM analyses of brood cell lining materials are made for all three species and suggest the presence of some fibrous components, possibly silk, as in some other colletids. The ichneumonid Grotea sp. is recorded parasitizing brood cells of C. venticola. none