Abstract. . Morphological colour adaptation of pupae of the butterfly Inachis io L. (Lepidoptera: Nymphalidae) is controlled by a factor which reduces cuticular melanization (Biickmann & Maisch, 1987). This so‐called pupal melanization reducing factor (PMRF) is located throughout the entire central nervous system of prepupae (Stamecker et al., 1994). Extracts of abdominal ganglia also stimulated dose‐dependently lutein incorporation into pupal cuticle. In the bioassay higher doses were required to increase cuticular lutein content than to reduce melanization. Ligatures during the prepupal stage demonstrated two different critical periods for these pigmentation effects: an early one for melanization reduction and a late one for lutein incorporation. An initial chromatographic purification yielded only two adjacent fractions which contained both the PMRF and the stimulation of lutein incorporation activity. Therefore it is assumed that only one hormone with a dual function may be responsible for pupal pigmentation. Lutein content was found in gut, fat body, epidermis and haemolymph of I.io. Lutein incorporation into cuticle occurred within 1.5 days of the pupal moult when the cuticle was not yet fully sclerotized. Lutein content is significantly higher in cuticle of yellow pupae than of black ones.

Phenotypic plasticity in pupal colour occurs in three families of butter£ies (the Nymphalidae, Papilionidae and Pieridae), typically in species whose pupation sites vary unpredictably in colour. In all species studied to date, larvae ready for pupation respond to environmental cues associated with the colour of their pupation sites and moult into cryptic light (yellow^green) or dark (brown^black) pupae. In nymphalids and pierids, pupal colour is controlled by a neuroendocrine factor, pupal melanizationreducing factor (PMRF), the release of which inhibits the melanization of the pupal cuticle resulting in light pupae. In contrast, the neuroendocrine factor controlling pupal colour in papilionid butter£ies results in the production of brown pupae. PMRF was extracted from the ventral nerve chains of the peacock butter£y Inachis io (Nymphalidae) and black swallowtail butter£y Papilio polyxenes (Papilionidae). When injected into pre-pupae, the extracts resulted in yellow pupae in I. io but brown pupae in P. polyxenes. These results suggest that the same neuroendocrine factor controls the plasticity in pupal colour, but that plasticity in pupal colour in these species has evolved independently (convergently).

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N eurohorm one, C olor A daptatio n , Polyphenism , Interspecific Effects, Insects A pupal m elanization reducing factor (P M R F ) co n trols incorporation of pigm ents into the cuticle of pupae of the nym phalid butterfly, Inachis io, to a d ap t th eir col o ration to the background colors of th e ir p u p atio n sites. In the present paper, we rep o rt on th e presence of P M R F in the central nervous system (C N S) of fu rth er butterfly species which exhibit a pupal m orphological color adaptation. Interestingly, two b u tterfly species which do not show such an ad ap tatio n , and even two m oth species which pu p ate in cocoons also contained P M R F in their CNS. The ganglionic extracts of non-lepido p teran species did not show a PM R F activity. The oc currence of PM R F (or PM R F-like m olecules), therefore, may be restricted to the lepidopteran o rd er.