Proboscis morphology and food preferences in nymphalid butterflies (Lepidoptera: Nymphalidae)

Abstract

Many species of nymphalid butter¯ies only exceptionally visit¯owers and feed instead on tree sap, juice of rotting fruits and other decaying substances. To investigate whether the proboscis morphology of these non-¯ower-visiting Nymphalidae differs from that of nectarivorous butter¯ies, representatives from 64 nymphalid species with known feeding preferences were examined. Morphometric comparison of the proboscis revealed characteristic differences in proboscis length, tip-region length, wall composition, and number and shape of proboscis sensilla between these two feeding guilds. The investigated non-¯ower-visiting species belonging to Apaturinae, Limenitidinae, Morphinae, Brassolinae, Nymphalinae and Satyrinae, possess a relatively short and light-coloured proboscis which has a long tip-region with a great number of club-shaped sensilla styloconica. Densely arranged, these sensilla form a¯at brush located laterally from the openings into the food canal on the dorsal side of the tip-region. Among the non-¯ower-visiting species, a second type of proboscis was found in fruit-feeding Charaxinae the stout tip-region of which is equipped with more widely spaced sensilla styloconica. The investigated¯ower-visiting Heliconiinae, Nymphalinae, Satyrinae, Danainae and Ithomiinae are characterized by a slender, darker-coloured proboscis with a rather short tip-region bearing fewer sensilla styloconica in a loose arrangement. Discriminant analysis revealed that the tip-region length, the number of sensilla styloconica and the relative proboscis length are the most important discriminating variables between the¯ower-visiting and the nonower-visiting species. The proboscis morphology of nymphalid butter¯ies corresponds with certain feeding habits and allow us to make predictions on their food preferences. The`brush-tipped' proboscis seems to have a functional role in the accumulation of¯uid and the uptake of liquid from wet surfaces such as rotting fruits or tree sap. We conclude from the phylogeny of the examined taxa that this derived proboscis tip morphology evolved several times independently as an adaptation to the exploitation of new food resources.

Butterfly proboscis: combining a drinking straw with a nanosponge facilitated diversification of feeding habits

“…The lack of a terminal opening would prevent capillary rise, drawing into question the similarity of the proboscis to a drinking straw. The test butterflies also did not probe the porous substrates with the end of their proboscises, but instead pressed the dorsal surface of the distal region to the substrate, leaving the extreme apex unengaged; similar behaviour is characteristic of butterflies and moths feeding from rotting fruits and other wet substrates [2,[10][11][12].…”

Sugar receptor response of the food-canal taste sensilla in a nectar-feeding swallowtail butterfly, Papilio xuthus

“…Furthermore, in V. indica, sugar-sensitive neurons are widely distributed in the tarsal sensilla (Morita et al 1957;Takeda 1961), whereas only a small proportion of the trichoid sensilla located laterally on the tarsi respond to sugar in Pieris rapae (Städler et al 1995). Alternatively, many lepidopteran adults have visible styloconic contact chemosensilla on the outside of the proboscis (e.g., Städler et al 1974;Sellier 1975;Altner and Altner 1986;Paulus and Krenn 1996;Krenn 1998;Krenn et al 2001;Petr and Stewart 2004;Molleman et al 2005;Kvello et al 2006). Three electrophysiological investigations have revealed the presence of sugar-sensitive neurons in the styloconic sensilla and their role in feeding behavior (Städler and Seabrook 1975;Blaney and Simmonds 1988;Ômura et al 2008).…”

Noctuidae moths occurring in grape orchards in Serra Gaúcha, Brazil and their relation to fruit-piercing

“…These noctuid moths show proboscis tips with sensilla very similar to those found in fruit feeding Nymphalidae butterflies (Figs. 10,11 and 12) (Krenn et al 2001;Knopp & Krenn 2003).…”