Journal of Insect Behavior, Vol. 13, No. 2, 2000 Short Communication Effects of Host Substrate and Vibration Cues on Ovipositor-Probing Behavior in Two Larval Parasitoids of Tephritid Fruit Flies Jian J. Duan 1,2,3 and Russell H. Messing 1 Accepted September 23, 1999; revised November 3, 1999 KEY WORDS: larval parasitoids; Opiinae; host selection; host searching; host patch; microhabitat(s); oviposition. INTRODUCTION Parasitoid host searching involves a hierarchy of behavioral responses to stimuli associated with both hosts and their habitats. One aspect of host- searching behavior involves the detection of hosts within a patch or micro- habitat. For parasitoids that attack hosts concealed within plant tissues, ovipositor-probing often is an essential element of host-searching behavior (Vet and van Alphen, 1985; van Dijken and van Alphen, 1998). Studying the stimuli affecting such behavior will help our understanding of behavioral and ecological mechanisms governing the process of parasitoid host se- lection. Diachasmimorpha tryoni (Cameron) and its congener, D. longicaudata (Ashmead), are koinobiont endoparasitoids, which attack late instar larvae of several fruit-infesting tephritid flies (Wharton, 1997). Both species have been widely used in classical and augmentative biological control programs against tephritid pests such as Ceratitis capitata (Wiedemann), Bactrocera 1 University of Hawaii, Department of Entomology/Kauai Agricultural Research Center, 7370- A Kuamoo Road, Kapaa, Kauai, Hawaii 96746. 2 Current address: Monsanto Company, Ecological Technology Center/V2C, 800 North Lind- bergh, St. Louis, Missouri 63167. 3 Correspondence should be sent to Jian J. Duan, Monsanto Company, Ecological Tech- nology Center/V2C, 800 North Lindbergh, St. Louis, Missouri 63167; e-mail: Jian.J.Duan@ Monsanto.com 175 0892-7553/00/0300-0175$18.00/0  2000 Plenum Publishing Corporation