SUMMARYThree satellite DNAs previously isolated from the entomopathogenic nematodesSteinernema carpocapsae, Heterorhabditis bacteriophoraandHeterorhabditis indicusgive hybridization signals only with theS. carpocapsae, H. bacteriophoraandH. indicuspopulations tested, indicating that these satellite sequences are species-specific. Because of their reiteration and their variabilities, we have shown that these sequences are able to discriminate at the interspecific level between theSteinernemaandHeterorhabditisspecies, but also at the intraspecific level betweenS. carpocapsaestrains. Furthermore, in simple squashed nematode experiments, we are able to unambiguously identifyS. carpocapsae,H. bacteriophoraandH. indicuspopulations. This last procedure is effective even on a single infective juvenile, with the main advantage that it avoids time-consuming DNA extractions.