Mouthparts of heliconius butterflies (LEPIDOPTERA : NYMPHALIDAE) : a search for anatomical adaptations to pollen-feeding behavior

Proboscis length, the length of the tip, the number and length of the various sensilla throughout the proboscis, and the size and shape of the labial palpi were compared in 25 species of pollen-feeding and non-pollen-feeding Heliconiinae (Lepidoptera, Nymphalidae). The mouthparts of pollen-feeding species (all belonging to the genera Heliconius and Laparus) do not have structures exclusive to them. However, in comparison with non-pollen-feeding Heliconiiti, the pollen-feeding species have a significantly longer proboscis without elongation of the tip-region ; the bristle-shaped sensilla trichodea 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 possibly associated with pollen-feeding behavior. The biological role of these features is discussed and the evolution of this unique feeding behavior among Lepidoptera is considered in the context of the phylogenetic relationships among genera of Heliconiini.