Effect of curvature on wetting and dewetting of proboscises of butterflies and moths

Abstract

Proboscises of butterflies are modelled as elliptical hollow fibres that can be bent into coils. The behaviour of coating films on such complex fibres is investigated to explain the remarkable ability of these insects to control liquid collection after dipping the proboscis into a flower or pressing and mopping it over a food source. By using a thin-film approximation with the air–liquid interface positioned almost parallel to the fibre surface, capillary pressure was estimated from the profile of the fibre surfaces supporting the films. The film is always unstable and the proboscis shape and movements have adaptive value in collecting fluid: coiling and bending of proboscises of butterflies and moths facilitate fluid collection. Some practical applications of this effect are discussed with regard to fibre engineering.

Ultramorphological Comparison of Proboscis and Associated Sensilla of Scotogramma trifolii and Protoschinia scutosa (Lepidoptera: Noctuidae)

“…This elastic effect combined with the tightly linking cuticular processes may hold the resting position of the proboscis. Coiling and bending not only help package and protect the proboscis, but also provide additional means to optimize fluid intake [42].…”

Self-assembly of the butterfly proboscis: the role of capillary forces

“…We periodically have observed lepidopterans in our colonies that have deformed wings and proboscises that remain uncoupled and distally withered, particularly under dry rearing conditions. We have shown that Lepidoptera can conserve fluids, including saliva, by bending and coiling the proboscis [13]. When saliva is alternately pumped into and retracted from the food canal, water could be lost to evaporation, especially in diurnal Lepidoptera exposed to the sun.…”

“…When saliva is alternately pumped into and retracted from the food canal, water could be lost to evaporation, especially in diurnal Lepidoptera exposed to the sun. Bending and coiling the proboscis during assembly, however, facilitate fluid collection at the permeable dorsal and ventral legular bands [13]. Movement of fluid to the legular bands would promote not only capillary attraction but also re-entry of the fluid into the food canal, thus counteracting any tendency for fluid to remain on the larger evaporative surface of the outer galeal walls.…”

“…The butterfly pushes the drop back and forth and coils and uncoils the proboscis, adjusting the coil radius to ensure that the drop is placed in a position to hold the branching galeae together. We have previously discussed the physical mechanisms of drop formation on the inner margin of the coiled proboscis [13].…”

Janus Interface Materials: A Critical Review and Comparative Study

“…And, the butterfly proboscis is a natural macropatterned surface with an inner liquid channel and a hydrophobic outer side enabling efficient feeding. , It was found out that the external surface of the proboscis of buttterflies and moths has a sharp boundary separating a hydrophilic drinking region and a hydrophobic nondrinking region. , This type of wetting dichotomy falls within the category of macropatterned surface and facilitates fluid uptake from nutrient-rich resources such as floral nectar . The butterfly proboscis is composed of two C-shaped, elongated fibers called galea, which are joined together by cuticular domains, legulae, at the top (dorsal) and bottom (ventral) medial edges, as shown in Figure .…”