Morphological fine tuning of the feeding apparatus to proboscis length in Hesperiidae (Lepidoptera)

The form and function of the hesperiid feeding apparatus was studied in detail. The butterflies in the family Hesperiidae are of particular interest because the longest proboscis ever recorded in Papilionoidea was found in the Neotropical genus Damas. We focused on the functional morphology by comparing proboscis morphology as well as size and composition of both the stipes pump and the cibarial suction pump in skippers with short and extremely long proboscis. Results revealed that all studied Hesperiidae have the same proboscis micromorphology and sensilla endowment regardless of the proboscis length. However, the numbers of internal muscles of the proboscis, the morphology of the stipes pump as well as the pumping organs for nectar uptake are related to the proboscis length. We conclude that the low number of tip sensilla compared to proboscis length is responsible for remarkably longer manipulation times of long‐proboscid species during flower visits. The organs for proboscis movements and nectar uptake organs are well tuned to the respective proboscis length and are accordingly bigger in species with a proboscis that measures twice the body length.     

Functional constraints on the evolution of long butterfly proboscides: lessons from Neotropical skippers (Lepidoptera: Hesperiidae)

Extremely long proboscides are rare among butterflies outside of the Hesperiidae, yet representatives of several genera of skipper butterflies possess proboscides longer than 50 mm. Although extremely elongated mouthparts can be regarded as advantageous adaptations to gain access to nectar in deep‐tubed flowers, the scarcity of long‐proboscid butterflies is a phenomenon that has not been adequately accounted for. So far, the scarceness was explained by functional costs arising from increased flower handling times caused by decelerated nectar intake rates. However, insects can compensate for the negative influence of a long proboscis through changes in the morphological configuration of the feeding apparatus. Here, we measured nectar intake rates in 34 species representing 21 Hesperiidae genera from a Costa Rican lowland rainforest area to explore the impact of proboscis length, cross‐sectional area of the food canal and body size on intake rate. Long‐proboscid skippers did not suffer from reduced intake rates due to their large body size and enlarged food canals. In addition, video analyses of the flower‐visiting behaviour revealed that suction times increased with proboscis length, suggesting that long‐proboscid skippers drink a larger amount of nectar from deep‐tubed flowers. Despite these advantages, we showed that functional costs of exaggerated mouthparts exist in terms of longer manipulation times per flower. Finally, we discuss the significance of scaling relationships on the foraging efficiency of butterflies and why some skipper taxa, in particular, have evolved extremely long proboscides.     

The proboscis of eye-frequenting and piercing Lepidoptera (Insecta)

The external structures of the proboscis are investigated in eye-frequenting species of Noctuidae, Geometridae and Pyralidae by means of scanning electron microscopy. They are compared with non-eye-frequenting representatives of these families. In Noctuidae, highly specialized fruit-piercing, skin-piercing blood-sucking, and sweat-feeding representatives have been included. All hemi- and eulachryphagous species have a soft proboscis tip which is characterized by few sensilla and strongly elongated, dentate plates of the dorsal galeal linkage. The latter structures leave broad gaps between them that lead into the food canal at the tip. This arrangement permits the uptake of fluid suspensions such as lachrymal fluid, wound exudates and pus. The modified dorsal galeal linkage is regarded as an adaptation for this highly derived feeding habit. The rough surface of the proboscis is likely to cause irritation and possible mechanical damage to the conjunctiva and cornea which results in an increased lachrymal flow and production of pus. In contrast to fruit-piercing and skin-piercing Noctuidae, there are no erectile structures on the proboscis of eye-frequenting species.—The comparison with related non-eye-frequenting species demonstrates that the particular morphology of the proboscis tip in lachryphagous moths evolved convergently in different families of Leipdoptera.     

One proboscis,two tasks: Adaptations to blood-feeding and nectar-extracting in long-proboscid horse flies (Tabanidae,Philoliche)

Female Pangoniinae in the tabanid fly genus Philoliche can display remarkably elongated proboscis lengths, which are adapted for both blood- and nectar-feeding. Apart from their role as blood-sucking pests, they represent important pollinators of the South African flora. This study examines the morphology of the feeding apparatus of two species of long-proboscid Tabanidae: Philoliche rostrata and Philoliche gulosa – both species display adaptations for feeding from a diverse guild of long-tubed flowers, and on vertebrate blood. The heavily sclerotised proboscis can be divided into two functional units. The short, proximal piercing part is composed of the labrum-epipharynx unit, the hypopharynx and paired mandible and maxilla. The foldable distal part is composed of the prementum of the labium which solely forms the food canal and is responsible for nectar uptake via the apical labella. The proboscis works as a drinking straw, relying on a pressure gradient provided by a two-part suction pump in the head. Both proboscis and body lengths and suction pump dimensions show a significantly correlated allometric relationship with each other. This study provides detailed insights into the adaptations for a dual diet using an elongated sucking proboscis, and considers these adaptations in the context of the evolution of nectar feeding in Brachycera.     

Adaptations for nectar‐feeding in the mouthparts of long‐proboscid flies (Nemestrinidae: Prosoeca)

The insects with the longest proboscis in relation to body length are the nectar‐feeding Nemestrinidae. These flies represent important pollinators of the South African flora and feature adaptations to particularly long‐tubed flowers. The present study examined the morphology of the extremely long and slender mouthparts of Nemestrinidae for the first time. The heavily sclerotized tubular proboscis of flies from the genus Prosoeca is highly variable in length. It measures 20–47 mm in length and may exceed double the body length in some individuals. Proximally, the proboscis consists of the labrum–epipharynx unit, the laciniae, the hypopharynx, and the labium. The distal half is composed of the prementum of the labium, which solely forms the food tube. In adaptation to long‐tubed and narrow flowers, the prementum is extremely elongated, bearing the short apical labella that appear only to be able to spread apart slightly during nectar uptake. Moving the proboscis from resting position under the body to a vertical feeding position is accomplished in particular by the movements of the laciniae, which function as a lever arm. Comparisons with the mouthparts of other flower visiting flies provide insights into adaptations to nectar‐feeding from long‐tubed flowers. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.     

Groundplan Anatomy of the Proboscis of Butterflies (Papilionoidea, Lepidoptera)

The anatomy of the proboscis was studied in representatives of all major subfamilies of Papilionoidea and several outgroup taxa which included Hesperiidae, Hedylidae and Geometroidea. In all species the cross-sectional outline of the tapering proboscis continuously changes from proximal to the tip while the central food canal, formed by the concave medial galeal walls, retains its oval shape. Each galea contains three types of muscles, a branching trachea, nerves, sensilla, and at least one longitudinal septum. We focused on the varying arrangement and distribution of the intrinsic galeal muscles from the basal galeal joint to the tip region. The plesiomorphic condition of the galeal composition of Papilionoidea is regarded to include one basal intrinsic muscle in the basal joint region and two series of intrinsic muscles, i.e. the lateral intrinsic galeal muscles and the median intrinsic galeal muscles, both series extending from the proximal region to the tip region. The plesiomorphic arrangements of the intrinsic muscle series are found in all representatives of Papilionidae, in one species of Lycaenidae (sensu lato), in many Nymphalidae (sensu lato), and in all outgroup species. Three apomorphic character states are distinguished regarding the presence and extension of the median intrinsic galeal muscles. (1) Present up to 35% of the proboscis length and absent distally in Pieridae, Lycaeninae (Lycaenidae), Satyrinae (Nymphalidae), and Danainae (Nymphalidae). (2) Present in the proximal third of the proboscis and again near the tip between 80 and 90% of the proboscis length in the examined Heliconiinae (Nymphalidae). (3) Completely absent, as in one lycaenid species from the subfamily Riodininae.     

Functional morphology and movements of the proboscis of Lepidoptera (Insecta)

Summary The mouthparts of Lepidoptera were investigated in a number of species by morphological and cinematographical methods. Both the galeae (which compose the proboscis) and the basal maxillary components (stipites) were studied in the resting position, in motion, and during feeding. In the resting position the proboscis is coiled so tightly that the surfaces of the consecutive coils are in close contact and the outermost coil touches the ventral side of the head. Cuticular processes of the galeal wall interlock between the coils in this position. In the investigated species they occur on the galeal wall and on the ventral side of the head in varying number and distribution. By the extension of the basal galeal joint, the coiled proboscis is released from its resting position and is elevated continuously. It uncoils in 3–5 steps which effect the entire length simultaneously. Each uncoiling step occurs synchronously with a compression of the stipital tubes on either side of the body. These compression movements pump hemolymph into the galeae. In all investigated Lepidoptera the uncoiled proboscis shows a distinct downward bend at a certain point which is also detectable in anaesthetized or freshly killed animals in some species. This feeding position and the movements of the uncoiled proboscis are similar in all species despite the intrinsic galeal muscles being variously arranged in the galeal lumen in different Lepidoptera. When comparing cross-sections through corresponding regions of coiled and uncoiled proboscises, the curvatures of the dorsal galeal walls remain unchanged. Coiling of the proboscis starts at the tip and progresses to the base. After coiling the proboscis tightly beneath the head, the diameter of the spiral widens due to its elastic properties until the proboscis props itself against the ventral side of the head. This elastic effect combined with the interlocking cuticular processes seems to be responsible for the resting position of the proboscis.Abbreviations an antenna - bre bend region - ca cardo - ci cibarium - cl clypeus - co complex eye - cp cuticular process - dre distal region - esm external tentoriostipital muscle - fc food canal - fst flat part of the stipes - ga galea - hs horizontal septum - igm intrinsic galeal muscles - ism internal tentoriostipital muscle - la labium - lap labial palpus - lr labrum - mxp maxillary palpus - ne nerve - pi pilifer - pom primary oblique galeal muscles - pr proboscis - pre proximal region - sa salivarium - se sensillum - som secondary oblique galeal muscles - st stipes - stl stipital lamella - te tentorium - tr trachea - tst tubular part of the stipes - vm ventral membrane - vs vertical septum     

Proboscis sensilla of the black cutworm Agrotis ypsilon (Rottemberg) (Lepidoptera: Noctuidae)

Proboscis sensilla are important for feeding biology in Lepidoptera, and are also valuable characters for species recognition and phylogenetic analysis. However, proboscis has not been satisfactorily explored in many groups in Lepidoptera so far. Here we examined the proboscis sensilla of the black cutworm Agrotis ypsilon (Rottemberg), a cosmopolitan agricultural pest of great economic significance, using scanning electron microscopy. Three types of sensilla were found on the proboscis: sensilla chaetica, sensilla basiconica, and sensilla styloconica. Sensilla chaetica occur only on the external surface of the proboscis and become shorter and more scattered toward the tip. Sensilla basiconica are arranged in longitudinal rows on the external proboscis and one longitudinal row in the inner food canal. Sensilla styloconica are the most characteristic sensilla on the proboscis, consisting of a single sensory cone inserted at the top of a stylus with six or seven longitudinal ribs, and are concentrated on the tip region, and are much longer and more numerous in females than in males. The role of proboscis sensilla in the feeding habit prediction is briefly discussed.     

Vergleichende Morphologie des Schmetterlingsrüssels und seiner Sensillen — Ein Beitrag zur phylogenetischen Systematik der Papilionoidea (Insecta, Lepidoptera)

Comparative morphology of the butterfly proboscis and its sensilla — a contribution to the phylogenetic systematics of Papilionoidea (Insecta, Lepidoptera) The morphology of the proboscis was investigated in more than 70 European representatives of Papilionoidea using light microscopy and scanning electron microscopy. The composition of the proboscis wall, its surface structures, as well as the shape and distribution of the different types of sensilla are compared. Special attention is given to the tip region and the diversity of the sensilla styloconica. Plesiomorphic features of the proboscis of Papilionoidea were found to include vertically extended exocuticular ribs composing the galeal wall, cuticular spines restricted to the ventral side of the proximal galea, and two rows of fluted sensilla styloconica restricted to the tip region. Apomorphic features of the proboscis in Papilionidae are three rows of small sensilla styloconica. The presence of cuticular spines all over the galeae was identified as an autapomorphy of Pieridae. Possible apomorphies of Nymphalidae are oblique exocuticular ribs of the galeal wall and the great number and length of the sensilla styloconica (significant at p < 0.01, t-test). A possible synapomorphy of Lycaenidae and Riodinidae are cuticlar spines up to the distal galeae. Distinct transformation series of sensilla styloconica give evidence that divergent evolutionary trends led from fluted shafts to a multitude of other shapes in Papilionidae, Nymphalidae (sensu lato), and Lycaenidae. Long smooth-shafted, club-shaped sensilla styloconica, bearing apical spines, are found in Nymphalinae, Apaturinae and Limenitidinae. Highly derived sensilla styloconica evolved in Heliconiinae and Melitaeini, which are arranged in only one row in both taxa. Their shafts are smooth, flattened and bear an excentral sensory cone. Further apomorphic character states are dented flutes which evolved several times, independently from each other in Satyrinae, Lycaeninae and Riodinidae. The results are discussed in a systematical context and provide the basis for a better understanding of the function of different morphological structures of the proboscis in feeding.     

The extremely long-tongued neotropical butterfly Eurybia lycisca (Riodinidae): proboscis morphology and flower handling

Few species of true butterflies (Lepidoptera: Papilionoidea) have evolved a proboscis that greatly exceeds the length of the body. This study is the first to examine the morphology of an extremely long butterfly proboscis and to describe how it is used to obtain nectar from flowers with very deep corolla tubes. The proboscis of Eurybia lycisca (Riodinidae) is approximately twice as long as the body. It has a maximal length of 45.6?mm (mean length 36.5?mm?±?4.1?S.D., N?=?20) and is extremely thin, measuring only about 0.26?mm at its maximum diameter. The proboscis has a unique arrangement of short sensilla at the tip, and its musculature arrangement is derived. The flower handling times on the preferred nectar plant, Calathea crotalifera (Marantaceae), were exceptionally long (mean 54.5?sec?±?28.5?S.D., N?=?26). When feeding on the deep flowers remarkably few proboscis movements occur. The relationship between Eurybia lycisca and its preferred nectar plant and larval host plant, Calathea crotalifera, is not mutualistic since the butterfly exploits the flowers without contributing to their pollination. We hypothesize that the extraordinarily long proboscis of Eurybia lycisca is an adaptation for capitalizing on the pre-existing mutualistic interaction of the host plant with its pollinating long-tongued nectar feeding insects.     

Adhesion and Suction Functions of the Tip Region of a Nectar-drinking Butterfly Proboscis

In this study,we investigated the dynamic functions of the tip region of the butterfly proboscis through which liquid is sucked during liquid feeding.The microstructures and flow patterns in the tip region of the proboscis were in vivo analyzed.The tip region can be divided into two functional sections:namely adhesion and suction sections.The liquid adheres to the adhesion section during liquid suction.Although the tip region has numerous slits connected to food canal of the proboscis,liquid is mainly sucked through the suction section,which section is submerged in the fluid pulled by the adhesion section and then successfully imbibes liquid.To check the dynamic functions of the tip region,we fabricated a suction tip model having adhesion and suction parts.The in vitro model experiments show that the hydrophilicity of the adhesion part and the existence of the suction inlet improve the liquid uptake driven by a suction pump.This study may provide insights for the biomimetic design of nectar-feeding butterflies.     

Proboscis sensilla in Vanessa cardui (Nymphalidae, Lepidoptera): functional morphology and significance in flower-probing

 Morphology and distribution of the proboscis sensilla in Vanessa cardui have been investigated in order to contribute to the understanding of flower-probing behaviour in butterflies. The proboscis has a bend region approximately one-third of the length from the base. A short tip region is characterized by rows of intake slits leading into the food canal. Along the dorsal, lateral and ventral sides of the proboscis, sensilla trichodea, sensilla basiconica and sensilla styloconica are distributed in varying patterns depending on their distance from the b ase. The medial food canal bears one longitudinal row of sensilla basiconica only. The bristle-shaped sensilla trichodea are longer in the proximal region of the proboscis and become gradually shorter towards the tip. They are most frequent in number near to the bend region and near the beginning of the tip region. Sensilla basiconica arranged in longitudinal rows increase in number the more distal they are on the proboscis. The tip region is characterized by rows of sensilla styloconica on the dorsal side whereas the sensilla trichodea are mostly restricted to the ventral side. The ultrastructure suggests that the aporous sensilla trichodea function as mechanosensilla while the uniporous sensilla basiconica act as contact chemosensilla. The sensilla styloconica are regarded as bimodal contact chemo/mechanosensilla since their sensory cones are equipped with a single terminal pore and a tubular body at the base. The mouthpart sensilla appear to provide tactile cues on the positioning of the proboscis and on the degree of its insertion into a floral tube. Furthermore, they receive chemical stimuli on the availability of nectar and on the immersion status of the food canal. Accepted: 12 September 1997     

Flies and concealed nectar sources: morphological innovations in the proboscis of Bombyliidae (Diptera)

Bee-flies (Bombyliidae) have morphological adaptations of the mouthparts to particular floral traits. To investigate this the short, plesiomorphic proboscis of Hemipenthes morio was compared with the long, apomorphic proboscis of Bombylius major . A novel feeding position enables B. major to use flowers that open to the side as additional nectar sources. The new horizontal feeding position is enabled by the prolonged ventral base of the proboscis. Bombylius major exploits deep corolla tubes with an elongate proboscis, and an increased efficiency in both the suction pumps and the sealing mechanisms of the proboscis. The exploitation of narrow corolla tubes is made possible by the shift from a sponging feeding mode, exhibited by H. morio , to the exclusively sucking mode in B. major . Besides quantitative changes in the proportions of the different proboscis components, labellar movements as well as the structures of saliva distribution are changed along with this shift. The labial musculature of B. major does not significantly differ from the plesiomorphic state, since both examined species do not only feed on nectar, but also on pollen.     

Interactions between hawkmoths and flowering plants in East Africa: polyphagy and evolutionary specialization in an ecological context

Hawkmoths (Lepidoptera, Sphingidae) are considered important pollinators in tropical regions, but the frequency and degree of reciprocal specialization of interactions between hawkmoths and flowers remain poorly understood. Detailed observations at two sites in Kenya over a two‐year period indicate that adult hawkmoths are routinely polyphagous and opportunistic, regardless of their proboscis length. About 700 individuals of 13 hawkmoth species were observed visiting a wide range of plant species at the study sites, including 25 taxa that appear to be specifically adapted for pollination by hawkmoths. We estimate that 277 plant species in Kenya (c. 4.61% of the total angiosperm flora) are adapted for pollination by hawkmoths. Floral tube lengths of these plants have a bimodal distribution, reflecting the existence of two hawkmoth guilds differing in tongue length. Hawkmoths exhibited strongly crepuscular foraging patterns with activity confined to a 20‐min period at dusk and, in some cases, a similar period just before dawn. Corolla tube length appears to act as a mechanical filter as the longest‐tubed plants were visited by the fewest hawkmoth species and these were exclusively from the long‐tongued guild. Tube length showed a strong positive relationship with nectar volume, even after phylogenetic correction, which implies that plants with long corolla tubes are under selection to offer relatively large amounts of nectar to entice visits by polyphagous long‐tongued hawkmoths. Our study shows that diffusely co‐evolved pollination systems involving long‐tongued hawkmoths are clearly asymmetrical, with plants exhibiting a high degree of floral specialization, while hawkmoths exhibit polyphagous behaviour. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 199–213.     

Salivary glands and salivary pumps in adult Nymphalidae (Lepidoptera)

The salivary glands and salivary pumps were investigated by means of dissection and serial semithin sections in order to expose the anatomy and histology of Nymphalidae in relation to feeding ecology. The paired salivary glands are tubular, they begin in the head, and extend through the thorax into the abdomen. The epithelium is a unicellular layer consisting of a single cell type. Despite the uniform composition, each salivary gland can be divided into five anatomically and histologically distinct regions. The bulbous end region of the gland lies within the abdomen and is composed of highly prismatic glandular cells with large vacuoles in their cell bodies. The tubular secretion region extends into the thorax where it forms large loops running backward and forward. It is composed of glandular cells that lack large vacuoles. The salivary duct lies in the thorax and also shows a looped formation but is composed of flat epithelial cells. The salivary reservoir begins in the prothorax and reaches the head. Its cells are hemispherical and bulge out into the large lumen of the tube. In the head the outlet tube connects the left and right halves of the salivary gland, and its epithelial cells are flat. The salivary pump lies in the head ventral to the sucking pump and leads directly into the food canal of the proboscis. It is not part of the salivary gland but is derived from the salivarium. Both the thin cuticle of the roof of the salivary pump and the thick bottom are ventrally arched. Paired muscles extend from the hypopharyngeal ridges and obviously serve as dilators for the pump. A functional interpretation of the salivary pump suggests that when not in use, the dilators are not contracted and the pump is tightly closed due to its own elasticity. When the dilator muscles repeatedly contract, the saliva is forced forward into the food canal of the proboscis. The salivary gland anatomy was found to be similar to other Lepidoptera. Furthermore, the histology of the salivary glands is identical in all examined butterflies, even in the species which exhibit specialized pollen-feeding behavior.     

小菜蛾成虫喙管感器的超微结构及其神经元中枢投射

【目的】明确小菜蛾Plutella xylostella成虫喙管感器的形态结构及感器神经元的投射。【方法】利用扫描电子显微镜观察小菜蛾成虫喙管结构和感器,利用神经回填技术和激光共聚焦显微镜观察喙管感器神经元在脑部的投射。【结果】小菜蛾成虫喙管上存在毛形感器(两种亚型)、腔锥形感器、锥形感器、刺形感器和栓锥形感器5种不同类型的感器。毛形感器表面光滑,分布于外颚叶外侧,可分为毛形感器Ⅰ型和Ⅱ型两种亚型,其中Ⅰ型比Ⅱ型长;锥形感器分布于喙管外表面,由一个感觉锥和一个短的圆形基座组成;腔锥形感器仅分布于食管内侧,只有一个粗短感觉锥而无基座;刺形感器由一个细长的感觉毛和一个圆形基座组成,表面无孔,分布于喙管的外表面;栓锥形感器是昆虫喙管上最典型的感受器,集中分布于喙管顶端区域,感器顶部凹腔伸出一个单感觉锥。此外,喙管上的感觉和运动神经元投射到初级味觉中枢咽下神经节。【结论】本研究阐明了小菜蛾成虫喙管感器的类型、分布和形态特征及其感器神经元在脑部的投射形态,为深入了解小菜蛾喙管感器的生理和功能奠定了基础。     

Form,function and evolution of the mouthparts of blood-feeding Arthropoda

This review compares the mouthparts and their modes of operation in blood-feeding Arthropoda which have medical relevance to humans. All possess piercing blood-sucking proboscides which exhibit thin stylet-shaped structures to puncture the host's skin. The tips of the piercing structures are serrated to provide anchorage. Usually, the piercing organs are enveloped by a soft sheath-like part which is not inserted. The piercing process includes either back and forth movements of the piercing structures, or sideways cutting motions, or the apex of the proboscis bears teeth-like structures which execute drilling movements. Most piercing-proboscides have a food-canal which is separate from a salivary canal. The food-canal is functionally connected to a suction pump in the head that transports blood into the alimentary tract. The salivary canal conducts saliva to the tip of the proboscis, from where it is discharged into the host. Piercing blood-sucking proboscides evolved either from (1) generalized biting-chewing mouthparts, (2) from piercing mouthparts of predators, or plant sap or seed feeders, (3) from lapping or sponging mouthparts. Representatives of one taxon of Acari liquefy skin tissue by enzymatic action. During feeding, many blood-feeding arthropods inadvertently transmit pathogens, which mostly are transported through the discharged saliva into the host.     

Anatomy of the oral valve in nymphalid butterflies and a functional model for fluid uptake in Lepidoptera

The food canal of the proboscis of Lepidoptera serves for the uptake of nutrient fluids and the discharge of saliva. A valve was discovered at the entrance to the sucking pump in the head that separates these countercurrent flows in nymphalid butterflies. Three species of Nymphalidae were examined by dissections and light microscopic serial semithin sections. The sucking pump is a unit composed of three structures: (1) the oral valve, which is a projection of the epipharynx extending into the anterior cibarial lumen, (2) the expandable lumen, and (3) the posterior sphincter valve which controls influx into the oesophagus. Based on the microanatomical results, a functional model is presented to account for the uptake and swallowing of fluids and for the control of the salivary flow into the food canal of the proboscis. Dilator muscles of the sucking pump expand the lumen by pulling on the muscular dorso-anterior side. This opens the oral valve and fluid can be drawn into the lumen from the food canal of the proboscis. Circular compressor muscles which attach to both sides of the sclerotized ventro-posterior wall of the sucking pump reduce the size of the lumen; passively they close the oral valve and press fluid through the relaxed posterior sphincter opening into the oesophagus. According to this model saliva can be discharged into the food canal during the swallowing phase. The oral valve and pumping unit are similar in all studied species despite the fact that saliva presumably plays a special role in the derived pollen-feeding behaviour of one of them, viz. Heliconius melpomene.     

Proboscis musculature in the butterfly Vanessa cardui (Nymphalidae, Lepidoptera): settling the proboscis recoiling controversy

Krenn, H. W. 2000. Proboscis musculature in the butterfly Vanessa cardui (Nymphalidae, Lepidoptera): settling the proboscis recoiling controversy. —Acta Zoologica (Stockholm) 81 : 259–266 The proboscis of Vanessa cardui (Nymphalidae) contains two basal galeal muscles and two different series of numerous oblique muscles. Both muscle series extend from the proximal region up to the tip‐region; the individual muscles of each series run a constant course throughout the proboscis. In contrast to other butterflies, the knee bend region does not have additional types of muscles. The analysis of shock‐frozen proboscises reveals that the dorsal wall is arched outwardly in the uncoiled, feeding position whereas in the coiled, resting position the dorsal proboscis wall is flat or concave. This results in a significantly greater cross‐sectional area due to the significantly greater dorso‐ventral diameter in uncoiled proboscises. After freezing the proboscis in its distal region, it can still be uncoiled, however, it cannot be fully recoiled. These morphometric and experimental results indicate that the oblique proboscis muscles are responsible for recoiling the proboscis to the resting position.     

Restricted diet breadth of the larvae of Antheraea assamensis and the role of the labrum‐epipharynx and galeal sensilla

The silkworm, Antheraea assamensis Helfer (Lepidoptera: Saturniidae), grows primarily on Persea bombycina and Litsea polyantha. To understand if the restricted diet breadth is due to the specific role of gustatory sensilla of the larvae of A. assamensis, the same fifth instar larvae retaining only labrum‐epipharynx or galeal sensilla were subjected to food choice tests. The foods used were leaves of two host‐plant and two non‐host‐plant species. Mean per cent consumption and per cent of choosing larvae were used as parameters for drawing conclusions. The finding indicated involvement of the labrum‐epipharynx for acceptance and galeal sensilla for rejection of a non‐host‐plant species. Scanning electron microscope studies revealed the presence of two sensilla on the galea, one lateral and one medial sensilla styloconicum and two gustatory sensilla in the epipharynx of A. assamensis. The study revealed the key role of galeal sensilla in the restrictive diet‐breadth of A. assamensis.