Plant Pigments identified in the Common Blue Butterfly

Abstract

FLAVONOIDS are rare in the animal kingdom, but Ford¹, using a simple colour test, suggested that they were present in a number of butterflies. A difficulty in characterizing the pigments is the fact that a large number of specimens, of the order of hundreds, is required, and it is not always possible to obtain one species in such large numbers. Morris and Thomson², using some 400 specimens, identified tricin and a glycoside of this flavone as well as a glycoside of another flavone, orientin, from the wings of the marble white butterflies Melanargia galathea. They found³ that the small heath butterflies Coenonympha pamphilus contained tricin both free and as glycoside but not orientin. The flavonoids seem to be obtained by the insects through the caterpillars feeding on a particular food host. Carotenoids, on the other hand, are well known in animals, and Goodwin⁴ has suggested that insects accumulate their dietary carotenoids as such or that they may be altered to form other carotenoids not found in the insects' food. A number of specimens of the common blue butterfly Polyommatus icarus Rott. were collected both in France and in England with a view to characterizing the flavonoids and the carotenoids and to comparing these with their food plants. One hundred specimens of P. icarus from Box Hill, Surrey, were feeding on rest harrow Ononis repens and those from St Martial, France (800 specimens), on a species of Anthyllis; both plants are members of the Leguminosae.