A unique protein of 23 kDa (Jf23) was found in the tarsus of the female swallowtail butterfly, Atrophaneura alcinous. Jf23 has 38% identity with a bilin-binding protein, which was found in the cabbage butterfly, Pieris brassicae, and which has two consensus sequences in common with the members of the lipocalin family, suggesting that it is a binding protein for lipophilic ligands. Western blot analysis showed that Jf23 was expressed only in the female, and not in the male. Electrophysiological response of the female tarsi was stimulated by methanolic extract of their host plant, Dutchman's pipe (Aristolochia debilis). The stimulated response was depressed by the presence of Jf23 antiserum. These results suggest that Jf23 is one of the chemosensory signaling proteins, which plays one or more roles in female butterfly oviposition.
