Mouthparts of Heliconius butterflies (Lepidoptera : Nymphalidae): A searchfor anatomical adaptations to pollen-feeding behavior

Proboscis length, the length of the tip, the number and length of the vario us sensilla throughout the proboscis, and the size and shape of the labial palpi were compared iri 25 species of pollen-feeding and non-pollen-feeding Heliconiinae (Lepidoptera, Nymphalidae). The mouthparts of pollen-feeding species tall belonging ts the genera Heliconius and Laparus) do not have st ructures exclusive to them. However, in comparison with non-pollen-feeding Heliconiiti, the pollen-feeding species have a significantly longer probosc is without elongation of the tip-region; the bristle-shaped sensilla tricho dea were found to be significantly more numerous and longer on the proximal and mid-region of the proboscis, while the sensilla of the tip-region are significantly shorter. In addition to these proboscis features, the labial palpi were shorter in the pollen-feeding species, which is likewise possibl y associated with pollen-feeding behavior. The biological role of these fea tures is discussed and the evolution bf this unique feeding behavior among Lepidoptera is considered in the context of the phylogenetic relationships among genera of Heliconiini. (C) 1998 Elsevier Science Ltd. All rights rese rved.