Carpilis barberi (Blatchley), Ptochiomera nodosa Say, Sisamnes claviger (Uhler), and S. contractus Distant are related seed bugs of the lygaeoid family Rhyparochromidae that once were placed in the same genus (Ptochiomera). The habits of only P. nodosa are well known. All four species (only one specimen of S. claviger was observed) were associated with the large, dense crowns of weeping lovegrass (Eragrostis curvula; Poaceae), an African bunchgrass that has been planted extensively in the southern United States. All species (excepting S. claviger) also were collected from crowns of native grasses of bunched growth habit; C. barberi also was associated with plants of other graminoid families: Cyperaceae (sedges) and Juncaceae (rushes). Arkansas, Georgia, Oklahoma, and South Carolina are new state records for C. barberi; Arkansas for P. nodosa and S. claviger; and Arkansas and Oklahoma for S. contractus. The three more frequently collected myodochines overwintered in crowns of weeping lovegrass (and other graminoids), where they would be protected from extremes in temperatures and have access to seeds of graminoids and other plants. Carpilis barberi, S. claviger, and S. contractus can be added to the infrequently collected North American insects that have colonized the African E. curvula. Although considered invasive in certain regions of the world where it has been introduced, weeping lovegrass may help conserve native insect diversity in the southern United States.