Journal of Chemical Ecology, Vol. 22, No. 2, 1996 VOLATILE INFOCHEMICALS USED IN HOST AND HOST HABITAT LOCATION BY Cotesia flavipes CAMERON AND Cotesia sesamiae (CAMERON) (HYMENOPTERA: BRACONIDAE), LARVAL PARASITOIDS OF STEMBORERS ON GRAMINAE ADELE J. NGI-SONG, ~'* WILLIAM A. OVERHOLT z'4 PETER G.N. NJAGI, I MARCEL DICKE, 2 JONATHAN N. AYERTEY, -~ and WILBERT LWANDE f 1The International Centre of hzsect Physiology and Eeoh~gy (ICIPE) P.O. Box 30772. Nairobi. Kenya ~-Department of Entomology, Agricultural University P.O. Box 803l, 6700 EH, Wageningen, 77m Netherlands 3Crop Science Department, University of Ghana, Legon P. O~ Box 44, Accra. Ghana (Received March 20, 1995; accepted October 15, 1995) Abstract--Female Cotesiaflavipes Cameron and Cotesia sesamiae (Cameron) were attracted to odors in a Y-tube olfactometer from uninfested maize (Zea mays L.). sorghum lSorghum bicotor (L.)], and napier grass (Pennisetum purpureum SchumachL In dual choice tests, Cotesia.fluvipes showed a pref- erence for maize over sorghum, while maize and napier grass were equally attractive. In contrast, Cotesiu sesamiae preferred volatiles from sorghum and napier grass over those from maize. The two parasitoids were significantly more attracted to maize inli~sted with the stemborers, Chilo partellus (Swin- hoe), Chilo orichatcocilie/lus Strand, Sesamia catamistis Hampson. and Bus- seola fi~sca (Fuller), than uninfested maize. In dual choice tests, Cotesia flavipes and O~tesia sesamiae were unable to discriminate between odors from plants infested by the different species of stemborers. Key Words--Host location, host habitat location, Cotesia flavipes, Cotesia sesamiae, Hymenoptera, Bmconidae, cereals, parasitoid, stemborers, Lepi- doptera, Pyra[idae, Noctuidae, Y-tube olfactometer. *To whom correspondence should be addressed. "~Present address: IC1PE P.O. Box 30772. Nairobi, Kenya. 307 tJ()qS-O33Iz96102F~M)30750 ~) 5(~/0 ~ 1990 Ptcnum Publishing Corp~