RESPONSES OF 2 HYMENOPTERAN PREDATORS TO SURFACE-CHEMISTRY OF THEIR PREY - SIGNIFICANCE FOR AN ALKALOID-SEQUESTERING CATERPILLAR

Larvae of Uresiphita reversalis (Guenee) (Lepidoptera: Pyralidae) sequester quinolizidine alkaloids from their leguminous hosts and store them primarily in the cuticle. Stored alkaloids are lost with the last larval molt. Extracts of late-instar larvae and of pupae were applied to larvae of the potato tuber moth, Phthorimaea operculella (Zeller) (Gelichiidae), which are normally palatable to two hymenopteran predators, the Argentine ant, Iridomyrmex humilis (Mayr) (Formicidae), and the paper wasp, Mischocyttarus flavitarsus (Sauss.) (Vespidae). Larvae of P. operculella treated with alkaloid extracts of U. reversalis larval exuviae, or with surface extracts of whole larvae, were deterrent to both predators, compared to untreated prey. Extracts of pupal exuviae added to P. operculella, however, were not deterrent. P. operculella larvae treated with the authentic alkaloids sparteine and cytisine were also deterrent to these hymenopteran predators. Storage of small but concentrated amounts of plant secondary compounds in the cuticle appears to be an efficacious means of defense against at least two common predators of lepidopteran larvae.