Amino-acids in Nectar and their Evolutionary Significance

Abstract

IT has been known since ancient times that nectar, usually secreted from specialized glands within flowers, is utilized by anthophilous (flower-visiting) animals for the energy-providing sugars that it contains. It is usually assumed that protein-making materials will be obtained elsewhere, from larval feeding (Lepidoptera), from pollen (Hymenoptera—Apioideae) or (by vertebrates) from insects. However, some butterflies are known to be attracted to decaying flesh, faeces, urine and stagnant water¹ and well as sweat², while many take phloem-sap from a wound or honey-dew excreted by aphids¹. Moths are known to drink fruit juices, sweat, secretions from the eyes of animals, and even mammalian blood³. Unusual feeding-behaviour is shown by butterflies of the genus Heliconius which collect pollen, steep it in nectar, and subsequently ingest the amino-acids that diffuse from the grains⁴.