none Bioassay responses in Cotesia marginiventris (Cresson) females to materials derived from fall armyworm (FAW) larvae, Spodoptera frugiperda (J. E. Smith), were most intense for frass and somewhat less intense for larval and pupal cutical materials, scales, exuviae, silk, and oral secretion, with FAW larval hemolymph eliciting only a slight response. The highest percentage of ovipositor probing was caused by frass (100%) and moth scales (90%) Various types of corn-leaf damage when assayed alone did not produce responses as intense as when assayed in combination with frass, cuticle material, and oral secretion. Parasitoid response was some-what better to frass derived from FAW larvae feeding on corn and peanut leaves than from larvae feeding on the foliage of soybeans, Bermuda grass, cowpeas, or laboratory diet. Hexane and chloroform were better than methanol and water for extracting active material from FAW frass, and chloroform was the best of these solvents for extracting corn leaves. Integument; Integumentary derivatives; Sensory reception; Nutrition; Digestion; Defaecation; Behaviour; Communication; Chemical signals; Orientation; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships Spodoptera frugiperda (Noctuidae); Scales; Source of kairomones mediating host seeking by hymenopteran parasite; Faeces; Frass, source of kairomones mediating host seeking by parasite; Pheromones; Kairomone sources mediating host seeking by hymenopteran parasite; Hymenopteran parasites; Cotesia marginiventris; Sources of kairomones mediating host seeking by parasite; Host seeking; Cotesia marginiventris (Hymenoptera) parasite, role of kairomones Cotesia marginiventris (Braconidae); Chemoreception; Taxis; Kairomones from lepidopteran host, role in host seeking; Lepidopteran hosts; Spodoptera frugiperda; Sources of host kairomones mediating host seeking; Host seeking; Spodoptera frugiperda (Lepidoptera), role of host kairomones