Carotenoids and bile pigments in Danaid and swallowtail butterflies

The carotenoids found in adult kite swallowtails ( Graphium spp.) and the Danaid glassy tigers ( Ideopsis, Tirumala and Parantica ), butterflies with exposed blue/green pigmented wing membranes (which contain pterobilins) and a modified scale vestiture, were compared with those of related species of Papilios and Danaids with concealed wing membranes an an entire scale vestiture. It was found that both the kite swallowtails contained only lutein, and even lacked β-carotene, the first known instance among butterflies. This was presumably due to selective storage by the larva since the food-plant was found to be rich in varied carotenoids. A possible link between the high concentration of pterobilins in the wing membrane and the lack of carotenoids is discussed.