Diapause pupae of Papilio xuthus show color polymorphism, represented by diapause-green, orange, and brownish-orange types that are each associated with specific pupation sites. We investigated the role of the site of pupation on the induction of the development of orange types (or brownish-orange types), and the endocrine mechanism underlying the control of color polymorphism in short-day pupae. All short-day larvae of the wandering stage developed into orange or brownish-orange type pupae when they were placed in rough-surfaced containers after gut-purge. Utilizing a pharate pupal ligation between the thorax and abdomen, the endocrine mechanism underlying the control of color polymorphism was shown to involve a head-thorax factor (Orange-Pupa-Inducing Factor: OPIF) that induced orange types in short-day pupae. OPIF was bioassayed using the ligated abdomens of short-day pharate pupae. OPIF was extractable with 2% NaCl solution from 5th-instar larval ganglia complexes following the mesothoracic complex (TG(2,3)-AG(1-7)), but it could not be extracted with either acetone or 80% ethanol solution. OPIF may not exist in the brains of day-0 pupae or in brain-subesophageal ganglion and prothoracic ganglion complexes of 5th-instar larvae. The short-day pharate pupae responded to OPIF in a dose-dependent manner.