The infectivity, incubation time, and reproduction of three heterorhabditid nematodes, Heterorhabditis sp. Bacardis and FL2122 strains and H. bacteriophora Poinar HP88 strain were studied in two insect hosts, an apionid weevil, Cylas formicarius (F.), and a pyralid moth, Galleria mellonella (L.). Two of the nematodes, Heterorhabditis sp. Bacardis and FL2122 strains, were of tropical or subtropical origin, whereas the third nematode, H. bacteriophora HP88 strain, was of temperate origin. Infectivity did not differ among nematodes within each host; however, it did differ between hosts for the Bacardis strain. Cylas formicarius was more susceptible to this nematode than G. mellonella. Incubation times also did not differ among nematodes within hosts; however, incubation times were 3.2-4.3 d shorter in C. formicarius than in G. mellonella. Progeny production differed (although not significantly consistent) among nematodes and was highest for Heterorhabditis sp. Bacardis followed by the Heterorhabditis sp. FL2122 and H. bacteriophora HP88 in both hosts. Percentages of infected cadavers that produced progeny were consistently higher for the tropical and subtropical nematodes, Heterorhabditis sp. Bacardis and FL2122, than for the temperate nematode, H. bacteriophora HP88, in both hosts. Patterns of emergence from cadavers were consistent in G. mellonella; most progeny emerged by 23 d after inoculation and emergence lasted for up to 48 d after inoculation. Conversely, emergence patterns varied markedly in C. formicarius. Emergence lasted for up to 29 d after inoculation and peak emergence varied between 12 and 28 d after inoculation. Progeny production in C. formicarius was not related to the biomass of the host cadaver.