Search

Pollen feeding behaviors Heliconius and Laparus (Lepidoptera: Nymphalidae) represent a key innovation that has shaped other life history traits of these neotropical butterflies. Although all flower visiting Lepidoptera regularly come in contact with pollen, only Heliconius and Laparus butterflies actively collect pollen with the proboscis and subsequently take up nutrients from the pollen grains. This study focused on the behavior of pollen processing and compared the movement patterns with proboscis grooming behavior in various nymphalid butterflies using video analysis. The proboscis movements of pollen processing behavior consisted of a lengthy series of repeated coiling and uncoiling movements in a loosely coiled proboscis position combined with up and down movements and the release of saliva. The proboscis-grooming behavior was triggered by contamination of the proboscis in both pollen feeding and non-pollen feeding nymphalid butterflies. Proboscis grooming movements included interrupted series of coiling and uncoiling movements, characteristic sideways movements, proboscis lifting, and occasionally full extension of the proboscis. Discharge of saliva was more pronounced in pollen feeding species than in non-pollen feeding butterfly species. We conclude that the pollen processing behavior of Heliconius and Laparus is a modified proboscis grooming behavior that originally served to clean the proboscis after contamination with particles.

Evolutionary key innovations give organisms access to new ecological resources and cause rapid, sometimes spectacular adaptive radiation. The well known obligate pollination mutualism between yuccas and yucca moths is a major model system for studies of coevolution, and it relies on the key innovation in the moths of complex tentacles used for pollen collecting and active pollination. These structures lack apparent homology in other insects, making them a rare example of a novel limb. We performed anatomical and behavioral studies to determine their origin and found evidence of a remarkably simple mechanism. Morphological analyses of the tentacles and adjacent mouthparts in pollinators and closely related taxa showed that the tentacle appears abruptly in female pollinating yucca moths. Several morphological synapomorphies between the galeae, which constitute the characteristic lepidopteran proboscis, and the tentacle suggest that the tentacle evolved quickly through expression of the genetic template for the galea at an apical growth bud on the first segment of the maxillary palp. Behavioral data indicate that tentacle and proboscis movements are controlled by a shared hydraulic extension mechanism, thus no new mechanism was needed for tentacle function. Known developmental paths from other insects can explain the origin of this sex-specific key innovation in a few steps.

The Neotropical Heliconius butterflies are well known to supplement their nectar diet by active pollen collecting. They extract proteins and free amino acids from pollen grains, exhibiting a particular behavior that involves the use of a fluid of uncertain origin. It has been assumed that this fluid is either regurgitated nectar or saliva, because for anatomical reasons a butterfly is able to release only these two fluids through its proboscis. In an experimental approach, 27 individuals of Heliconius melpomene (L.) were given red-dyed sugar solution and subsequently we observed whether the fluid used in pollen feeding was dyed or not dyed. Because regurgitated nectar should contain sugar, fluid samples were taken from the proboscis of butterflies from natural populations in Costa Rica. Samples of 44 individuals from seven species were tested for the presence of fructose and glucose with the aid of aniline phthalate. This study is the first detailed investigation of the origin of the fluid used by Heliconius butterflies in pollen feeding. The results are discussed in terms of already existing hints in literature concerning the true nature of that fluid. [ABSTRACT FROM AUTHOR]

The mouthparts of the spoon-winged lacewing Nemoptera sinuata are adapted for the uptake of pollen and nectar. Form and function of the mouthparts are described, and the technique of food uptake is discussed in context with flower-visiting behaviour and floral architecture of the preferred flowers. The maxillae are the main organs for food uptake. The brush-shaped laciniae, galeae and maxillary palpi form a functional unit which can be extended by the action of the cardo-stipes joint. Video analyses of the mouthpart movements distinguished different patterns of maxillary motions which occur in nectar feeding or pollen collecting. The flower-visiting behaviour and the specialised mouthparts of the Nemopteridae are derived traits which probably evolved from predatory and biting/chewing mouthparts within the Neuroptera. [ABSTRACT FROM AUTHOR]

Abstract: This review deals with the morphology and function of adult insect mouthparts modified to feed on nectar, pollen or petals. Specialization to nectar-feeding is evident in formation of proboscides of various lengths and designs. Proboscides of many Hymenoptera and Diptera function according to adhesion mechanisms that load nectar onto extensible apical mouthpart regions before fluid is conveyed along the food canal to the mouth by capillarity and suction. Predominantly suctorial proboscides evolved once in Lepidoptera, probably twice in Coleoptera, variously in some Hymenoptera and several times with similar design in Diptera. Many of them are particularly long and have sealed food tubes, specialized apical regions, new proboscis resting positions and modified feeding movements. Mouthparts of obligate pollen-feeding insects can be characterized by modified mandibles, specialized bristles for pollen manipulation and elaborate feeding movements. Often saliva is crucial for pollen retention and ingestion. In Coleoptera, intact pollen is gathered by sweeping movements of mouthparts; in Diptera, it is suspended in saliva prior to suction. Pollen is crushed by asymmetrical mandibles in aglossatan Lepidoptera and one group of basal Hymenoptera. Pollen-piercing mouthparts occur in Thysanoptera and one group of Diptera. Some butterflies and few Diptera extract nutrients from pollen by mixing it externally with saliva on their mouthparts. No mouthpart specializations to petal-feeding are reported in flower-visiting insects. [Copyright &y& Elsevier]