Arthropods of French Guiana were examined to delineate the host range of a newly described species of an ectoparasitic nematode,Noctuidonema guyanenseRemillet&Silvain, of adult Lepidoptera. Moths in five families (Lasiocampidae, Noctuidae, Notodontidae, Pyralidae, and Sphingidae) harboredN. guyanense. Twenty-five species of Noctuidae were infected. Multiple species ofSpodopteraandMocisserved as hosts forN. guyanense. The most commonly infected hosts wereLesmone formularisHübner,S. dolichos(F.),S. frugiperda(J. E. Smith), andXanthopastis timais(Cramer). Lepidoptera in 19 families, including 121 species of Noctuidae, did not harborN. guyanense. Also, arthropods in 12 orders and 70 families of non-lepidopteran insects, 2 orders of Arachnida, and 5 families of Araneae were not infected byN. guyanense. It appears thatN. guyanenseis primarily an ectoparasite of moths in Noctuidae.