Influence of Dietary Lipids on Survival of Phyciodes phaon Butterflies (Lepidoptera: Nymphalidae)

Abstract

The Phaon crescent butterfly, Phyciodes phaon (Edwards), can be reared by placing newly-eclosed larvae on a pinto bean-based artificial diet; however, the adults fail to reproduce. Addition of 10% (w/w) of freeze-dried leaves of the host plant, Phyla nodiflora (L.) Greene, to the artificial diet approximately doubled the number of adults produced, and females oviposited viable eggs. Addition of wheat germ oil, linseed oil, or olive oil to the artificial diet without host plant tissue also increased survival to the adult stage, but adult females failed to oviposit. Larvae and adults reared from the artificial diet with addition of any one of the oils contained a higher quantity of linolenic acid in their body lipids than those reared on the artificial diet without additional oil. Leaves of the larval host plant are especially rich in the polyunsaturated fatty acids, linoleic acid and linolenic acid; whereas, the pinto bean diet is relatively low in these fatty acids, especially linolenic acid. Addition of synthetic β-sitosterol, stigmasterol, and campesterol, the sterols identified in the host plant leaves, to the artificial diet improved neither larval nor adult survival, and adult females did not oviposit. The factor (or factors) present in host plant leaves and acquired during larval feeding that enables reproduction of adults remains to be identified.