The neotropical cornstalk borer (NCB), Diatraea lineolata (Walker), is a widely distributed species of the economically important genus Diatraea (Lepidoptera: Pyralidae) (Rodriguez-del-Bosque et al. 1988). A recent study on the parasitization of NCB in the corn agroecosystem of northern Tamaulipas, Mexico, revealed a minimal impact of native parasites. No pupal parasites were detected, and only three larval parasites appeared sporadically causing negligible levels of parasitization. The braconid larval parasite Cotesia flavipes (Cameron) was introduced into the corn agroecosystem of northern Tamaulipas in 1985, and rapidly became the most important parasite of both NCB and the sugarcane borer, D. saccharalis (F.) (Rodriguez-del-Bosque 1988). However, the impact of this exotic parasite was greatest on D. saccharalis, dictating the need for introduction of additional natural enemies against NCB. The successful establishment of potential parasites in this area could be limited by their ability to develop on diapausing NCB larvae, which are present during both summer and winter. Diapause of NCB is characterized by a change from a spotted to an immaculate morph, triggered by host plant maturation (Rodriguez-del-Bosque 1988). We investigated the suitability of NCB pupae and diapausing larvae to several exotic parasites. This report serves as a precursor for further detailed investigations and as a guide for selecting the best parasites for trial colonization. Small-scale laboratory tests were conducted from January to May 1988 to determine the host suitability of NCB to several exotic larval and pupal parasites, cultured at the Biological Control Facility, Department of Entomology, Texas A&M University, as part of a biological control program aimed at graminaceous stalkborers in Texas. Diapausing NCB larvae used in the tests were field collected from maturing cornstalks in Rio Bravo, Tamaulipas, Mexico, placed in 20-ml cups with artificial diet (Martinez et al. 1988), and transported to College Station, Texas. Pupae (1-2 days old) were obtained from a NCB colony maintained in College Station (Rodriguez-del-Bosque 1988). Larval parasites tested included the braconids Digonogastra kimballi (Kirkland) and Allorhogas pyralophagus Marsh from Mexico, C. flavipes and Rhacanotus roslinensis Lal from Pakistan, Apanteles minator Muesebeck from Bolivia, and the bethylid Goniozus natalensis Gordh from South Africa. The braconids all developed successfully on nondiapausing (spotted) NCB larvae in preliminary trials. Goniozus natalensis was not tested against nondiapausing NCB larvae. Pupal parasites were the eulophids Trichospilus diatraeae Cherian & Margabandhu from India (founder culture obtained from Florida, U.S.A.) and Pediobiusfurvus Gahan from Kenya, and the ichneumonid Xanthopimpla stemmator Thunberg from Asia (founder culture obtained from Mauritius). Although T. diatraeae has previously been reared from NCB pupae (Bennett & PschornWalker 1970), information on parasitization, emergence, progeny, and developmental time was not reported. Twenty hosts (pupae or diapausing larvae) were used to determine NCB suitability and developmental time (host exposure to adult parasite emergence) for each parasite, except X. stemmator, in which 81 pupae were used. Host larvae and pupae were held at constant 26-+?0.5?C and 14:10 (L:D) photoperiod during and after exposure to parasites. Host larvae were exposed for 24 h to >20 parasite females held in Plexiglas cages