Pachyerepoideus vindemmiae Rondani is an ectoparasitic idiobiont parasitoid attacking puparia of many cyclorrhaphous Diptera. This study investigated its potential impact as a facultative hyperparasitoid of four other primary tephritid fruit fly parasitoids in Hawaii, Fopius arisanus (Sonan), Diachasmimorpha longicaudata (Ashmead), Diachasmimorpha kraussii Fullaway, and Psyttalia concolor (Szepligeti). F. arisanus attacks host eggs while the latter three species attack host larvae, and they all emerge as adults from host puparia. P. vindemmiae successfully developed from host puparia previously parasitized by all of the other four tephritid parasitoids. There were no significant differences in developmental time or body size of P. vindemmiae adults reared from these secondary host species. However, P. vindemmiae reared from the secondary hosts were smaller than those from the tephritid hosts Bactrocera cucurbitae (Coquillett) or Bactrocera latifrons (Hendel); and were larger than those reared from Drosophila melanogaster Meigen. Female P. vindemmiae developed faster on D. melanogaster but slower on Ceratitis capitata (Wiedemann) than on the other hosts. P. vindemmiae did not prefer to attack unparasitized hosts rather than hosts previously parasitized by F arisanus, and there was no difference in offspring survival and sex ratio between the wasps reared from the primary and secondary host species. Among the three distinctly different size host species, B. latifrons, C capitata, and D. melanogaster, P. vindemmiae preferred to attack the smallest host (D. melanogaster), but invested more female offspring on the largest host (B. latifrons). There was no difference in offspring survival between those reared on D. melanogaster and C capitata, but the adult emergence rate was lower in B. latifrons than in the other two species. The flexible body growth and less discriminative nature of P. vindemmiae indicate that it has the potential for host range expansion and thus non-target impact to other beneficial parasitoids of Diptera. [copyright] 2004 Elsevier Inc. All rights reserved. Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Land zones; USA; Oceanic islands; Pacific Ocean islands Tephritidae; Hymenopteran parasites; Diachasmimorpha; Fopius & Psyttalia; Hymenopteran hyperparasitoid host expansion & non target impact; Hawaii, hyperparasitoid host expansion & non target impact Diachasmimorpha kraussii; Diachasmimorpha longicaudata; Fopius arisanus; Psyttalia concolor (Braconidae ); Hymenopteran parasites; Pachycrepoideus vindemmiae; Hyperparasitoid host expansion & non target impact; Hawaii; Dipteran hosts; Tephritidae Pachycrepoideus vindemmiae (Pteromalidae); Hymenopteran hosts; Diachasmimorpha; Fopius & Psyttalia; Hyperparasitoid; Hawaii; Hyperparasitoid of Hymenoptera, host expansion & non target impact none