Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd.) Maesen & Almeida, a close relative of soybean, Glycine max (L.) Merr., is an adventive and widely distributed weed in the southeastern United States. Conventional wisdom says that native arthropods do not feed heavily on kudzu, but recent evidence has indicated this is not the case. To better understand the interaction of kudzu and native insects, the biology of the soybean looper, Pseudoplusia includens (Walker), was compared on kudzu and soybean. Insects fed on kudzu had higher mortality, longer development times with supernumerary molts, and lower pupal weights than those fed on soybean. Rearing for up to three generations on either plant host had an effect on length of development time but did not affect other measured parameters. Foliage consumption did not differ between treatments, and nutritional quality of soybean and kudzu did not differ. The instar at which insects were transferred from artificial diet to either kudzu or soybean significantly influenced development time, number of instars, foliage consumption, and pupal weights, with instar 4 being the optimum stage for transfer. In an oviposition test, females readily oviposited on kudzu in a no choice test, but when both kudzu and soybean were provided, more eggs were deposited on soybean than on kudzu. Our studies show that although kudzu is an acceptable host, soybean is a preferred and better quality host.