Structure & Development 31 (2002) 103–120 www.elsevier.com/locate/asd

Evolution of the suctorial proboscis in (Masarinae, )

Harald W. Krenna,*, Volker Maussb, John Planta

aInstitut fu¨r Zoologie, Universita¨t Wien, Althanstraße 14, A-1090, Vienna, Austria bStaatliches Museum fu¨r Naturkunde, Abt. Entomologie, Rosenstein 1, D-70191 Stuttgart, Germany

Received 7 May 2002; accepted 17 July 2002

Abstract The morphology and functional anatomy of the mouthparts of pollen wasps (Masarinae, ) are examined by dissection, light microscopy and scanning electron microscopy, supplemented by field observations of flower visiting behavior. This paper focuses on the evolution of the long suctorial proboscis in pollen wasps, which is formed by the glossa, in context with feeding from narrow and deep corolla of flowers. Morphological innovations are described for flower visiting , in particular for Masarinae, that are crucial for the production of a long proboscis such as the formation of a closed, air-tight food tube, specializations in the apical intake region, modification of the basal articulation of the glossa, and novel means of retraction, extension and storage of the elongated parts. A cladistic analysis provides a framework to reconstruct the general pathways of proboscis evolution in pollen wasps. The elongation of the proboscis in context with nectar and pollen feeding is discussed for aculeate Hymenoptera. q 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Mouthparts; Flower visiting; Functional anatomy; Morphological innovation; Evolution; Cladistics; Hymenoptera

1. Introduction Some have very long proboscides; however, in contrast to , the proboscis is formed only by the glossa and, in Evolution of elongate suctorial mouthparts have some species, it is looped back into the prementum when in occurred separately in several lineages of Hymenoptera in repose (Bradley, 1922; Schremmer, 1961; Richards, 1962; association with uptake of floral nectar. They can be found, Osten, 1982; Carpenter, 1996/1997; Gess, 1998). The for example, in various ‘symphytans’ (Jervis and Vilhelmsen, traditional classification of the Masarinae, dating back to 2000), parasitoid (Jervis, 1998), sphecids (Ulrich, Saussure (1854), was based on the misunderstanding that Paragia 1924), , Sapygidae, (Osten, 1982, 1991) the glossa of one group (based on ) cannot be retracted at all and the glossa of the other group (based on and in many bees (Michener, 1944, 2000). In Vespidae, Masaris ) can be retracted into the prementum. Carpenter’s despite the fact that the adults of both sexes obtain at least (1996/1997) study of the Paragiina clarified the morpho- some nourishment from floral nectar (Kugler, 1970; Proctor logical misunderstanding and demonstrated that the glossa et al., 1996), a very long elongate suctorial proboscis is not in all groups is retractable. The separation of the Masarinae common, except in Eumeninae (Osten, 1982) and Masarinae. into two main lineages, the Paragiina and Masarina, The Masarinae, or pollen wasps, are unique among the however, was upheld in that study by other features. vespids for their -like habits of provisioning each larval Currently the Masarinae contains 14 genera with about 300 brood cell with pollen and nectar. Female pollen wasps use species (Carpenter 1982, 2001) and is divided into the their mouthparts to gather pollen and nectar from flowers Gayellini and Masarini. The latter tribe consists of and for nest construction (Gess and Gess, 1992; Gess, Paragiina (Australian region only), Masarina (widespread 1996, 2001; Mauss, 1996, 2000; Mauss and Mu¨ller, 2000). except Australia) and Priscomasarina, which was estab- lished to accommodate a newly discovered species from * þ þ Corresponding author. Tel.: 43-1-4277-54497; fax: 43-1-4277- Namibia (Gess, 1998, Fig. 1). 9544. E-mail addresses: [email protected] (H.W. Krenn), volker. The evolution of an elongate proboscis occurred at least [email protected] (V. Mauss). twice in the Masarinae. Elongation of the proximal part of

1467-8039/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S1467-8039(02)00025-7 104 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120

braunsi Schulthess, Celonites peliostomi Gess and Quarti- nioides sp. (classification after Carpenter (2001),who regards Quartinioides as a subgenus of Quartinia ). Fresh specimens were fixed in 70% ethanol or Duboscq- Brasil solution (Romeis, 1989). Whole mount preparations of the mouthparts were made from dissected heads. They were soaked in diluted lactic acid at 40–50 8C for 1–2 days, washed in distilled water, and embedded in polyvinyl lactophenol without dehydration on glass slides. The preparations were covered with glass slips and dried at 50 8C. Serial semithin-section technique was used to examine mouthpart anatomy with light microscopy and to recon- struct the possible functional mechanisms of glossal move- ments. The isolated heads were dehydrated with acidified DMP (2,2-dimethoxypropane) and acetone, then embedded Fig. 1. Dendrogram showing hypothesized phylogeny of Masarinae, in ERL-4206 epoxy resin under vacuum impregnation. combined from Carpenter (1982, 1989, 1993, 1996) and Gess (1998). Taxa in bold type are investigated in this study. Semithin sections were cut using diamond knives. They were stained with a mixture of 1% azure II and 1% the glossa or of the distal part thus defines two lineages, the methylene blue in an aqueous 1% borax solution for subtribe Masarina and Metaparagia (Paragiina) (Carpenter, approximately 1 min at 80 8C. Series of sagittal semithin 1996/1997). As a relatively small group of flower visiting sections were prepared for all the above listed species of Hymenoptera, the Masarinae offer the possibility to Masarinae. Preparations were made of P. decipiens and C. examine the pathways of mouthpart evolution in the context hispanicus individuals with retracted and extended probos- of nectar feeding. We focus on a comparative functional cides. The mechanism of glossal movements was studied in anatomy of the glossa in Masarini since in some genera it is thawed specimens of freeze-killed C. hispanicus and in relatively short yet retractable while in others it is extremely freshly collected C. lusitanicus, C. hispanicus and C. long. We delineate several morphological innovations fonscolombei. which are important for the formation and functioning of For viewing in the scanning electron microscope (SEM), a suctorial proboscis, in addition to discussing further fixed samples of P. decipiens, C. hispanicus, C. peliostomi evolutionary aspects of the proboscis in Hymenoptera. and Quartinioides sp. were dehydrated in ethanol and submerged in hexamethyldisilazane prior to air drying (Bock, 1987). A graphite adhesive tape was used to mount 2. Material and methods them on SEM viewing stubs. The samples were sputter- coated with gold and viewed in a Jeol JSM-35 CF SEM. 2.1. Field observation

Flower visiting behavior and water uptake were observed 3. Results in Ceramius fonscolombei Latreille, C. hispanicus Dusmet, C. lusitanicus Klug in Spain (Arago´n, Province Teruel: Barranco de Zorita, 19–26 June 1998; north of Almohaja, 3.1. Flower visiting behavior 16–18 June 1998; east of Los Iban˜ez, 7–12 June 2000; Rambla de Rio Seco, west of Valdecebro, 9–16 June 2000) The behavioral pattern exhibited by Ceramius on flowers and in C. tuberculifer Saussure in France (Alpes-de-Haute- differed according to the shape of the flower and whether Provence: Peyresq 19–28 July 1994; Montagne de Boules pollen or nectar was collected. On flowers with exposed 26–29 July 1994) in part with the aid of close-up binoculars anthers [Helianthemum spec. (Cistaceae) (C. lusitanicus and and documented by macro-photography (scale 1:1). C. hispanicus ); Reseda spec. (Resedaceae) (C. fonscolom- bei )] females primarily harvested pollen directly (Fig. 2), 2.2. Morphology their mandibles clasped and nibbled the anthers; their maxillae were visibly active during ingestion of the The mouthparts of females were examined using light loosened pollen. The proboscis was never extended. Pollen microscopy in Priscomasaris namibiensis Gess (Priscoma- uptake at zygomorphic flowers with hidden anthers (Lotus sarina), Paragia decipiens Shuckard (Paragiina), Ceramius corniculatus L. (Fabaceae) (C. hispanicus ); Dorycnium hispanicus and C. fonscolombei which are considered to be hirsutum (L.) Ser. (Fabaceae) (C. lusitanicus ); Teucrium basal representatives of Masarina, and several higher montanum L. (Lamiaceae) (C. tuberculifer )) was indirect; Masarina, i.e. Masarina familiaris Richards, Jugurtia pollen was brushed from the anthers or from parts of the H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 105

Figs. 2 and 3. Fig. 2: Ceramius lusitanicus female collecting pollen with mandibles and maxillae at a flower of Helianthemum organifolium (Lam.) Pers. Fig. 3: C. hispanicus female imbibing water from moist soil with extended glossa (arrow). body and brought between the mouthparts by movements of their heads above the main body axis (Fig. 3). When the forelegs, the distal parts of which form pollen brushes. imbibing water the outer surface of the glossa appears to be Although nectar uptake is difficult to verify, it can be covered with adherent water which resulted in shiny supposed to occur at several zygomorphic flowers with a reflections. deep tubular corolla (Marrubium supinum L., Nepeta nepetella L. (both Lamiaceae) (C. hispanicus ); Teucrium 3.2. Mouthpart morphology montanum (C. tuberculifer ); Echium vulgare L. (Boragina- ceae), Dorycnium hirsutum (C. lusitanicus )). The glossa The gross morphology of the head, mandibles and was never extended before the had put its head into the maxillae is briefly summarized for the investigated corolla of these flowers, but on some occasions it could be Masarinae. The surface of the head and exposed areas of observed that the glossa was still somewhat extended when the mouthparts are covered with long unbranched bristles. the wasp pulled its head back. The glossa was always Viewed frontally, the clypeus projects over the labrum. completely retracted shortly thereafter and wasps never flew Long bristles of the labrum protrude from under the clypeus off with extended mouthparts. Ceramius fonscolombei was (Figs. 4 and 8). When the mandibles are closed, they observed to visit the easily accessible flowers of Reseda, obscure the frontal view of the maxillae and labium except presumably for nectar uptake, since its short proboscis could for the tips of the glossa and palpi. The labium and maxillae be seen extended toward the nectar-bearing dorsal enlarge- are visible from the posterior view of the head (Fig. 7). The ment on the disc of the flower, with the mandibles slightly basal parts of the maxilla, i.e. the cardo and stipes, lie opened. between the labium and the head. The stipes is arched and Ceramius uses water to moisten the soil during particular tilted at a slight angle against the labium. Proximally it is stages of nest construction (Gess and Gess, 1992; Gess, attached to the apex of the cardo and distally it bears the 1996, 2001; Mauss and Mu¨ller, 2000). To collect water the lacinia, galea, and maxillary palpus which has six segments females of C. hispanicus (Fig. 3), C. lusitanicus and C. in P. namibiensis and five in P. decipiens. The lacinia is a fonscolombei landed at the edge of a water site or on damp large, flat lobe overlapping the anterior part of the galea. soil. They opened their mandibles and extended the glossa. The distal portion of the galea is composed of several plates, The extension process was very rapid. During the following one of which bears on the inner surface a longitudinal row of period of water uptake only the distal tip of the glossa bristles. Pollen grains are commonly found on this galeal reached the wet surface. Normally the proboscis was comb. The inner surface of the galea is basally continuous slightly bend ventrad. The distal bifurcated section of the with the preoral cavity, which is formed by the epipharynx, glossa was straight and parallel. On a few occasions the the underside of the labrum and the large muscular proboscis was bend slightly dorsally in C. lusitanicus with hypopharynx. The hypopharynx contains the voluminous the distal tip lying on the ground. The posture of the wasp infrabuccal pouch, which in some specimens was filled with depends on the length of its glossa. Females of C. pollen (Figs. 6 and 13). Parts of the lacinia and galea, which fonscolombei with a short proboscis lowered their heads are positioned near the infrabuccal pouch are responsible for close to the water surface, while individuals of C. pushing pollen grains into the mouth (Fig. 6). hispanicus and C. lusitanicus with a long proboscis raised The short-tongued mouthparts of P. namibiensis and P. 106 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120

Figs. 4–6. Fig. 4: Head of P. decipiens (Paragiina); mandibles (md) are open and the glossa (gl) is extended. Clypeus (cl) partly covers the labrum (lr). Fig. 5: Bifurcate glossa (gl) of P. decipiens (Paragiina) in dorsal view; paraglossae (pgl) lie laterally at the basis of the glossa; dorsal side of glossa bears transverse cuticular lamellae which enclose the food canal of the bifid distal region. Fig. 6: Longitudinal section through head of P. namibiensis (Priscomasarina). Glossa (gl) folded under the preoral cavity (poc). Infrabuccal pouch (ibp) filled with pollen grains; m. intralabialis posterior (mip) folds the posterior lingual plate (plp) against the prementum (pr); glossa rod (glr) is bent in posterior direction. Extension of the glossa is achieved by contraction of m. intralabialis anterior (mia) which permits the anterior lingual plate (alp) to revert back to its extended position parallel to the prementum. decipiens correspond in many features to the plesiomorphic occur in the morphology of the glossa which forms the condition for vespids, e.g. Euparagiinae (Bradley, 1922), principle organ of fluid uptake. The plesiomorphic glossa of Eumeninae (Richards, 1962; Osten, 1982) and vespids and basal pollen wasps can be morphologically (Kirmayer, 1909; Brocher, 1922; Duncan, 1939). The labial divided into a proximal section and a distal, often bilobed or palpus is 4-segmented, the glossa is bifid and has a length of bifurcated section with the acroglossal buttons. The anterior approximately 1.5 mm in P. decipiens (Figs. 4 and 5). The surface of the glossa bears transverse rows of flattened hair- glossa is short compared to the prementum, whereas the like cuticular structures, however, in the Masarini these are paraglossae are relatively large and conspicuous (Fig. 5). modified into lamella-shaped plates. The lamellae in The prementum is elongate and u-shaped with large median Priscomasaris transverse the entire glossal surface, while arches adjoining the hypopharynx on its lateral edges. The in Paragia, they are divided medially into two rows glossa emerges from the distal end of the prementum and is extending from the glossal base to the tips of the deeply flanked by the paraglossa, which arise from the paraglossal bifid glossa (Fig. 5). The food canal of the proximal section sclerite. Intermediate the glossa and the prementum on the of the glossa is a deep longitudinal pocket set between the posterior side is the large and strongly flexible ‘posterior lateral rows of lamellae. On the anterior surface of each lingual plate’ (Duncan, 1939) which arises out of the apical glossal lobe, the lamellae arch toward the hair-like cuticular prementum and leads into the short glossal rod; intermediate structures emerging from the posterior surface and together on the anterior side is the ‘anterior lingual plate’ (Duncan, they form a narrow food canal (Fig. 5). An acroglossal 1939) which is characterized by its lateral arms. button with associated sensilla is located on the posterior While the mandibles and maxillae are similar in form and apex of each glossal lobe. The paraglossa are elongate, function in all investigated Masarinae major differences extending beyond the proximal section of the glossa, and H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 107

Fig. 7. Schematic drawing of head of P. decipiens (Paragiina). Striped muscles indicate those responsible for glossal retraction (A, B), and glossal extension (C, D). (A) Posterior view, glossa retracted. (B) Longitudinal section of head; glossa retracted by contraction of m. intralabialis posterior (mip) and m. craniolabialis anterior (mca). (C) Posterior view, glossa extended. (D) Longitudinal section of head, glossa extended by contraction of m. intralabialis anterior (mia) and m. craniolabialis posterior (mcp). Occipital foramen (of); cardo (c); stipes (st); maxillary palpus (mxp); mandible (md); prementum (pr); paraglossa (pgl); glossa (gl), labial palpus (lp). their concave median surfaces laterally embrace the base of in the labium of Ceramius species, as compared to P. the glossa (Fig. 5). In both species, glossa and paraglossae decipiens, regards glossal length, formation of a closed food fold together in repose (Fig. 7). tube, increased flexibility at the articulation between the The plesiomorphic resting position of the labium is a z- basal glossa and prementum, and the resting position of the shaped fold (Figs. 6 and 7). When folded, the glossal base glossa. We investigated two species of Ceramius, the frontally closes the preoral cavity (Figs. 6 and 7). In this relatively short-tongued C. fonscolombei (glossal length position the glossa is bent toward the hypopharynx at a right 2 mm) and the long-tongued C. hispanicus with a glossal angle to the prementum. The posterior lingual plate is flexed length of 5.6 mm (^0.2; n ¼ 10). In both species, the against the prementum and the short glossal rod bends the cuticular structures of the glossa build an enclosed median distal bifurcated section of the glossa in the opposite food tube along its entire length and it can be retracted into direction (Fig. 6). the prementum. Despite variation in glossal length, the The musculature of the labium which is considered functional mechanisms presumed to be responsible for responsible for direct movements of the glossa is diagramed retraction and protraction appear identical, at least with in Fig. 7. The muscles are labeled according to origin and regard to internal anatomy. attachment sites and numbered after Matsuda (1965) with The elongate suctorial glossa of Ceramius and most other regard to probable homology within the Hymenoptera. higher Masarina can be functionally and morphologically Comparison of serial head sections with the glossa in divided into three sections: a short proximal section, a long retracted and extended positions enabled us to draw middle section, and a distal, usually bifurcated, section conclusions on the functional mechanism of glossal move- (Fig. 10). The proximal section of the glossa encompasses ments. The glossa is folded primarily by contraction of the posterior articulation to the prementum (Fig. 9). The musculus intralabialis posterior (M42), which folds back distal prementum connects via the ‘hinge plate’ (Duncan, the posterior lingual plate, and by contraction of m. 1939) to the well-sclerotized posterior lingual plate which is craniolabialis anterior (M34), which draws back the continuous with the glossal rod. The internal elastic glossal anterior lingual plate (Fig. 7B). Extension of the glossa is rod extends the entire length of the glossa to the bifurcated achieved by m. intralabialis anterior (M43) which permits section. The anterior side of the proximal glossa is the anterior lingual plate to revert back to its extended connected to the anterior lingual plate by a thin and flexible position parallel to the prementum, and by m. craniolabialis cuticle which allows the glossa to telescope under the posterior (M35), which originates on the clypeus and anterior lingual plate. Distally, the anterior lingual plate is extends at a right angle to the prementum. Its contraction forked to embrace the lateral base of the glossa which itself pulls the proximal prementum toward the proboscidial fossa is adjoined to the paraglossal sclerite as well as to the lateral of the head capsule and probably thus contributes to initial prementum processes. The posterior and lateral sides of the extension of the glossa (Fig. 7D). glossa are characterized by an elastic cuticular membrane Proboscis of Ceramius species. The major modification up to the middle of the glossa (Fig. 16). 108 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120

The food tube of the middle section is formed by two invaginates at the distal end of anterior lingual plate (Figs. longitudinal and adjacent rows of lamellae on the anterior 13 and 14), extending back beneath the plate near to surface. The arching lamellae of each row overlap the salivarium where it turns forward. The anterior lingual plate preceding ones and the two rows come together to form a extends as a long and narrow sclerite to the proximal end of completely closed median food tube that extends the entire the prementum (Figs. 13 and 14). The paraglossae are short length of the glossa (Figs. 11 and 16). The broad surfaces of and can be only partially retracted. the plates are finely sculptured, a feature that may help to The pronounced difference in labial musculature ensure a tight closure between the plates yet permit between P. decipiens and the Ceramius species concerns flexibility (Fig. 11). In the proximal section of the glossa, the course of the m. intralabialis anterior (M43). This the food canal widens, the lamellae are larger and the two muscle extends between the inner premental margin and the rows do not overlap as tightly as in the middle section. The anterior lingual plate. In Ceramius it is fan-shaped due to proximal widening opens into the preoral cavity which is the strongly u-shaped prementum and the elongation of the covered by the labrum and distal parts of the maxilla. At the anterior lingual plate. One part of this muscle extends from bifurcated section of the glossa, the food tube splits and the proximal end of the prementum to the anterior lingual continues along each glossal lobe (Figs. 12 and 16). Each plate at a right angle to the course of the prementum (Figs. food canal in this section is formed by the strongly curved 13 and 14). Another part extends from the lateral margin of and overlapping lamellae on the anterior side, while the the prementum to the anterior lingual plate at an oblique posterior side is formed by additional cuticular structures angle. Further portions of this muscle extend between the that curve upward from the underside of the glossa, together premental processes and the lateral arms of the anterior enclosing a narrow canal along the inner margin of each lingual plate. Together with the shape of the prementum, the glossal lobe (Fig. 16). They have small spines, possibly to thin fan-shaped muscles form a deep cavity or pouch in increase surface area. Fluids are probably taken up through which the glossa retracts (Fig. 14). the slits between the lamellae and between the hair-like A functional model for the mechanism of extension and structures (Fig. 12). The acroglossal buttons are reduced in retraction of the glossa (Fig. 17) was derived from size and bear numerous short conical sensilla each with a dissections and comparison of the sectional series in single terminal pore. specimens with the proboscis in retracted and extended In the retracted position, the glossa is almost entirely positions (Figs. 14 and 15). In Ceramius the contraction of withdrawn into the prementum and lodged underneath the the fan-shaped m. intralabialis anterior (M43) constricts the anterior lingual plate (Figs. 8, 9, 14 and 16). The glossa rod space between anterior lingual plate and the prementum and is connected to the prementum by the intervening hinge squeezes the premental pouch which envelopes the glossa plate and posterior lingual plate which permits two 908 (Fig. 15). In this manner, the glossa rod is moved forward flexions of the glossa (Fig. 9). First is the flexion of the hinge out of the pouch. Contraction of the anterior part of these plate on the prementum, and second the flexion between the muscles forces the entire anterior lingual plate forward, and hinge plate and posterior lingual plate, together they result the anterior side of the glossa turns inside out. Due to its in a reversal of the direction of the glossa (Figs. 13 and 14). elastic properties the glossa immediately projects forward to At about one third of its length the retracted glossa bends its full extent, as determined in freeze-killed and thawed about 1508 forward so that its anterior surface lies directly specimens. The role of the m. craniolabialis posterior under the anterior lingual plate, the tips of the glossal lobes (M35) is not entirely clear. Its contraction may pull the lie between the maxillae and mandibles. The membranous prementum deeper into the head cavity which would cuticle of the proximal glossa half is pulled into the contribute to the compression of the space between prementum and forms a cavity (Fig. 14). In cross-section, prementum and anterior lingual plate (Fig. 17). Opening the prementum is strongly u-shaped to provide space for the of the mandibles is a likely precondition for glossal loop of the retracted glossal rod. extension. According to the field observations the mandibles The anterior side of the glossa, which is connected to the were always observed to be open when the glossa was median area of the anterior lingual plate, retracts tele- extended (Fig. 3). scopically through the forked arms of the anterior lingual During the initial phase of retraction of the glossa, the plate. The flexible sleeve-like anterior surface of the glossa posterior lingual plate is folded back into the prementum by

Figs. 8–12. Fig. 8: Head of C. hispanicus (Masarina) in frontal view. Mandibles (md) closed; glossa retracted into prementum. Clypeus (cl) covers the labrum. Fig. 9: C. hispanicus (Masarina); distal portion of the labium in lateral view; left mandible and maxilla removed. Glossa retracted into prementum (pr), only glossal tips (gl) visible; posterior lingual plate (plp) at a right angle to hinge plate (hp) which is at a right angle to prementum. Clypeus (cl), mandible (md), labial palpus (lp), maxillary palpus (mxp). Fig. 10: Head of C. hispanicus (Masarina) in lateral view. Glossa (gl) extended; hinge plate (hp) and posterior lingual plate (plp) are extended outward forming the articulation of the glossa (gl) and prementum (pr); glossa tip (glt) is bifurcated; paraglossa (pgl) is short. Fig. 11: Cross cut through the middle section of the glossa. Overlapping cuticle lamellae form the food tube (ft) along the anterior side; the glossa rod (glr) provides stability to the glossa. Fig. 12: Bifurcate glossal tip in C. hispanicus. Each glossal half has a separate food canal formed by spiny cuticular structures; tip bears acroglossal button (ab). H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 109 110 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120

Figs. 13–16. Fig. 13: Ceramius fonscolombei (Masarina), longitudinal section through head. Relatively short glossa (gl) is held in resting position. Posterior lingual plate (plp) is folded and glossal rod (glr) is retracted into the prementum (pr). Anterior lingual plate (alp) is longer than retracted glossa. Paraglossa (pgl), clypeus (cl) and labrum (lr) form frontal closure of the preoral cavity (poc); distal plates of maxillae (mx) transport pollen into the infrabuccal pouch (ibp). Fig. 14: C. hispanicus (Masarina), longitudinal sections through the prementum (pr) with retracted glossa (gl). Glossal rod (glr) articulates with prementum via posterior lingual plate (plp) and hinge plate (hp); glossal tip (glt) at same level as paraglossa (pgl); long anterior lingual plate (alp) give H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 111

Fig. 17. Model of the functional mechanism of glossal movement in Ceramius. (A) Glossa retracts by contraction of m. intralabialis posterior (mip) and m. craniolabialis anterior (mca).(B) Glossa unfolds by contraction of m. intralabialis anterior (mia) and m. craniolabialis posterior (mcp). Areas of articulation between prementum (pr) and hinge plate (hp) and between hinge plate and posterior lingual plate (plp) are extended. Arrows indicate movements of mouthparts. contraction of m. intralabialis posterior (M42) (Fig. 17). At The principle morphology of the glossae and the basic a particular point the elastic properties of the glossal rod mechanism of retraction in all investigated higher Masarina force the glossa to suddenly slip into the premental pouch. is the same as described for Ceramius. The glossa is The membranous cuticle of the anterior side invaginates retracted between the prementum and the anterior lingual under the anterior lingual plate. The posterior side turns into plate, but due to its great length the looped glossa extends the prementum by the double flexion of the glossa (Fig. 17). beyond the proximal end of the prementum to a varying Contraction of m. craniolabialis anterior (M34) pulls back degree in the different species. A sac formed by mem- the anterior lingual plates and the lateral glossal base (Fig. branous cuticle (‘glossal sac’, Richards, 1962) is visible on 17). the posterior side of the head as a lightly colored sac behind Proboscis of higher Masarina. In most of the higher the more darkly sclerotized prementum. Masarine taxa, the glossa is longer relative to body length In J. braunsi,asinCeramius, the glossa lies in one great than in the previously discussed species. In J. braunsi and loop within the prementum and protrudes beyond the M. familiaris the glossa has a length of 3.0–3.3 mm which proximal end of the prementum and cardines (Fig. 18). The is equal to one third body length. In Quartinioides sp. it is musculature of the labium does not envelope the sides of about 4.9–5.0 mm long which is about as long as the body. the glossal pouch. The m. intralabialis anterior (M43) is

attachment site of m. intralabialis anterior (mia); m. intralabialis posterior (mip) attaches at posterior lingual plate. Fig. 15: C. hispanicus (Masarina), longitudinal sections through prementum (pr), glossa (gl) extended. The two articulations between prementum and hinge plate (hp) and between hinge plate and posterior lingual plate (plp) are extended. Anterior lingual plate (alp) pressed against prementum due to contraction of m. intralabialis anterior (mia) and m. craniolabialis posterior (mcp); m. craniolabialis anterior (mca) attaches at anterior lingual plate. Fig. 16: C. hispanicus (Masarina), cross-sections through the glossa in (A) the proximal half, (B) the distal half, and (C) the tip region. Cuticular structures of the lateral glossal wall form the food tube (ft) on the anterior side of the glossa. The glossal rod (glr) stiffens the glossa on the posterior side. The lumen of the glossa (gll) is voluminous in the proximal half and narrow distally; the bifid tip region has a double food tube formed by curved cuticular structures from both sides of the glossa. 112 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120

Figs. 18 and 19. Fig. 18: Longitudinal section through head of J. braunsi (Masarina). Glossal rod (glr) is retracted into a loop which bulges beyond the prementum (pr) and cardo (c). Posterior lingual plate (plp) is folded backward by m. intralabialis posterior (mip); hinge plate (hp) is bent against the prementum. Micrograph is composite of photos of two sections from the same series. Fig. 19: Longitudinal section through head of Quartinioides sp. (Masarina). The glossa (gl) is retracted in several loops into the prementum (pr); glossal tip (glt) frontally covered by distal plates of the maxillae (mx). m.intralabialis posterior (mip). smaller and extends only into the proximal third between the loops within the prementum (Fig. 19). In this species, as in anterior lingual plate and the prementum. This muscle is the examined Jugurtia and Masarina, the m. intralabialis composed of two portions, one runs obliquely in the anterior (M43) is weak and does not envelope the glossal posterior direction to the proximal/median region of the pouch. prementum, the other portion extends in a lateral direction and inserts on the lateral margin of the prementum. 3.3. Cladistics In M. familiaris the glossa sac is remarkably enlarged and arches over the hypostomal bridge. Due to the The Masarinae have been subjected to previous cladistic transparency of the cuticle, the loop of the glossal rod is analyses. In Carpenter’s (1982) phylogenetic study, which visible from outside. The stipites have processes directed was based on 50 characters and numerous vespid taxa toward the median sides behind the proximal end of the including the pollen wasps, the superfamily was prementum. In Celonites peliostomi the glossal sac is large reduced to the single family Vespidae with the following and extends well beyond the head. arrangement: Euparagiinaeþ(Masarinae þ (Eumeninae þ In Quartinioides sp. the prementum is rather flat, broad ( þ ( þ (Vespinae))))). The and rounded on the posterior side and extends with two Euparagiinae were removed from the masarids leaving slender arms over the lateral sides. No glossal sac is present. two tribes of pollen wasps, the Gayellini and Masarini. The In comparison to the short body length, the glossa of Gayellini were analyzed by Carpenter (1989). Carpenter Quartinioides sp. is extremely long and very thin, being (1993) presented a dendrogram of the Masarinae, based on about ten times as long as the prementum. The bifurcate about 50 unpublished characters in which Paragia þ section makes up about 85% of total glossal length. Metaparagia were the sister-group to the remainder of the Longitudinal sections through the head reveal that the Masarini. In an analysis of the Australian species of pollen glossa retracts into several longitudinal and transversal wasps, Carpenter (1996/1997) separated the Masarini into H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 113

Table 1 List of characters and character coding used in cladistic analysis of Fig. 20

Head 1. Clypeal dorsal margin: (0) straight; (1) bisinuate 2.Wing-shaped clypeus: (0) absent; (1) present 3. Eye emargination: (0) present; (1) absent 4. Number of male antennal articles: (0) thirteen; (1) twelve 5. Female mandibles: (0) quadridentate; (1) tridentate; (2) bidentate. Polarity as in Gess (1998) Mouthparts 6. Paraglossa: (0) about as long as or longer than proximal section of glossa; (1) shorter; (2) reduced or absent 7. Prementum: (0) longer or about as long as proximal section of glossa; (1) shorter than proximal section of glossa 8. Glossa: (0) shorter than head length; (1) longer than head length; (2) about as long or longer than body 9. Glossa retractable into prementum: (0) partially; (1) almost fully with one loop; (2) almost fully and coiled into several loops 10. Glossal sac: (0) absent; (1) moderate in size; (2) large extending beyond cardo. Ceramius was coded with state one; however, state two may be present in some species 11. Glossal anterior surface with: (0) transverse rows of hairs; (1) transverse rows of lamellae; (2) median food canal formed by non-overlapping lamellae; (3) median food tube formed by overlapping lamellae. Additive 12. Glossal lobe: (0) without processes; (1) with two rows of flattened processes forming a sponge-like extension; (2) flattened processes overlap and curve together to form a tube. Additive 13. Anterior lingual plate: (0) short; (1) long and narrow sclerite to the proximal end of the prementum 14. Acroglossal buttons: (0) present; (1) absent 15. Maxillary palpi: (0) six-segmented; (1) three-segmented; (2) two-segmented; (3) one-segmented. Additive. Character is variable in Paragiina and Ceramius

Mesosoma 16. Pretegular carina: (0) present; (1) absent. Polarity as in Carpenter (1996/1997) and Gess, 1998) 17. Propodeal spiracle: (0) lateral; (1) more or less dorsal 18. Male foretrochanter: (0) without process; (1) with process

Forewing 19. Marginal cell: (0) not narrower basally than apically; (1) 2r-rs curving basal to insertion of RS so that it is narrower 20. Submarginal cell number: (0) three; (1) two 21. CuA2 and A: (0) angled where meeting; (1) rounded together 22. First discal cell: (0) shorter than subbasal cell; (1) as long or longer than subbasal cell 23. CuA: (0) diverging from M þ CuA; (1) distal to insertion of cu-a; (2) based to insertion of cu-a 24. Cu-a: (0) transverse; (1) inserted on CuA and aligned with A 25. Longitudinal folding: (0) absent; (1) present Hindwing 26. Free apical section of A: (0) present; (1) absent 27. Jugal lobe: (0) present; (1) reduced

Biology 28. Larvae feed on: (0) prey; (1) pollen and nectar

two subtribes, Paragiina (containing Paragia and Meta- subtribal arrangement of taxa as presented in Gess (1998). paragia ) and Masarina. The analysis of Gess (1998) with The clade Paragiina þ Masarina is supported by two consideration of 17 characters split the Masarini into three synapomorphies, both features of the glossa, i.e. food subtribes with Priscomasaris as only member of a new canal of proximal glossa formed by lamellae (character 11, subtribe, Priscomasarina, which formed a sister group state 2), and the presence of a food canal on the glossal lobes relation to remaining subtribes, Paragiina þ Masarina. (character 12, state 2). A processed male foretrochanter The present analysis utilizes 28 characters (Table 1) (character 18) was regarded as another potential synapo- many of which are adopted from Gess (1998) and Carpenter morphy in the analysis of Gess (1998), however, the (1982, 1996/1997). Three multistate characters (11, 12, 15) character plotting is equivocal in this study, since it is representing transformation series were coded as additive. present in Paragia and Ceramius but not the other (Euparagiinae) was selected as the outgroup. investigated Masarina. Computer analysis on the data matrix of Table 2 using The cladistic analysis shows that the trend toward NONA (Goloboff, 1993) yields one cladogram (Fig. 20) elongation of the proboscis is accompanied by morphological with a step length of 49, consistency index of 0.79 and innovations, such as the presence of lamellae on the anterior retention index 0.81. Cladograms were examined and glossa (character 11, state 1) leading to the formation of a characters plotted using WinClada (Nixon, 2000). median food canal between the lamellae (character 11, state The cladogram in Fig. 20 confirms the tribal and 2). Both states are necessary preconditions for the formation 114

Table 2 Distribution of 28 characters (Table 1) used in cladistic analysis (Fig. 20). Character numbers in bold type

Head Mouthparts

Clypeal Shape of Eye Number Female Para- Premen- Glossa Glossa Glossal Lamellae Glossal Anterior Acro- Maxillary dorsal clypeus, margin- of mandibles, glossa tum length, retracted sac, on glossa, lobe lingual glossal palpi margin, 1 2 ation, antennal 5 length, length, 8 into 10 11 with plate, 13 buttons, segment 3 articles, 6 7 premen- food 14 number, 103–120 (2002) 31 Development & Structure Arthropod / al. et Krenn H.W. 4 tum, tube, 15 9 12

Euparagia 000020000000000 Gayella 100000000000000 Priscomasaris 001110000011000 Paragia 001110000022000 Ceramius 010111111132100 Celonites 000122111232111 Masarina 000111111232102 Jugurtia 000111111232102 Quartinioides 000122122032103 Quartinia 000122111132103

Mesosoma Forewing Hindwing Biology

Pretegular Propodeal Male Marginal Submar- CuA2 First CuA, Cu-a, Longitu- Free Jugal Larval carina, 16 spiracle, foretro- cell, 19 ginal and discal 23 24 dinal apical lobe, food, 17 chanter, cell A, 21 cell, folding, section 27 28 18 number, 22 25 of A, 20 26 Euparagia 0000001000000 Gayella 1000000100011 Priscomasaris 1000101210111 Paragia 0111111210111 Ceramius 0010101210111 Celonites 0100101211111 Masarina 0000101010111 Jugurtia 0000101010111 Quartinioides 0000101011111 Quartinia 0000101011111 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 115

Fig. 20. Cladogram of Masarinae based on data in Table 2. Subtribes indicated on right margin. Character numbers are given above line and character states below. The outgroup is represented by Euparagia. Morphological innovations associated with the production of a suctorial proboscis are formation of a food canal, a looped glossa, and a closed food tube. Glossa retracted in several loops is an autapomorphy in Quartinioides. of the closed food tube of the elongated glossa (character 11, glossa which has cuticular structures that allow uptake of state 3) in Masarina. Furthermore, the lengthening of the nectar and water, presumably, in large part by adhesion. The anterior lingual plate (character 13, state 1) seems to be functional morphology which enables a passive uptake of crucial for the development of novel mechanisms enabling liquids, at least until the vicinity of the preoral cavity where the extension of the glossa out of the glossal sac. Elongation pharyngeal suction takes over, is regarded as plesiomorphic of the glossa in Masarina is also associated with shortening of for the Masarinae since it appears to differ little from that of the paraglossa (character 6, states 1 and 2). The presence of a other wasps in Euparagiinae (Bradley, 1922), Eumeninae moderate-sized protruding glossal sac (character 10, state 1) (Richards, 1962; Osten, 1982) or Vespinae (Kirmayer, is interpreted by the analysis as a synapomorphy of the 1909; Brocher, 1922; Duncan, 1939). The higher Masarina Masarina; however, it is absent in Quartinioides.Alarge possesses an elongate suctorial proboscis with morphologi- protruding sac (character 10, state 2) is regarded as cal innovations of the labium, i.e. the lamellar structures of convergent in Celonites and the clade Jugurtia þ Masarina, the glossa forming a food tube, the specialized apex and however, it could be a synapomorphy of the higher Masarina basiglossal articulation, as well as the shape and muscles of with a reversion in Quartinia and a loss in Quartinioides. the prementum. Morphological innovations enabling mouthpart elonga- tion are often novel solutions to biomechanical problems, 4. Discussion such as formation of suction tubes, mechanisms of move- ment and new resting positions for the long proboscis. Some 4.1. Morphological innovations in the suctorial proboscis of of these will be referred to below. pollen wasps Suction. The elongate proboscis in operates like a drinking-soda straw, in that fluid is sucked along an Flower visiting behavior in insects is connected with a air-tight tube due to pressure created by the muscular host of modifications in the mouthparts. Many of these are pharyngeal pump (Kingsolver and Daniel, 1995). The same adaptations for pollen collection and ingestion as well as analogy applies to the glossa of higher pollen wasps, where nectar consumption. Radical transformations of the mouth- the lamellar cuticle structures of the glossa, which must be parts are evident in various forms of elongation that are homologous to the rows of hair structures on the glossa of associated with nectar feeding from flowers with a deep other Vespidae, form the long and air-tight median food corolla (Schremmer, 1961; Jervis, 1998; Jervis and tube. Other mechanisms for ensuring the air-tightness of a Vilhelmsen, 2000). The evolution of an elongate suctorial food canal include the coming together or the interlocking glossa from a short homologous condition is exemplified in of different parts, either temporarily, like in bees, or the pollen wasps. The basal taxa of the pollen wasps, i.e. permanently. Permanent linkage of the two halves of the Gayella, Priscomasaris, Paragia possess a relatively short proboscis is achieved in Lepidoptera by a series of hooks 116 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 and overlapping cuticle plates (Hepburn, 1971; Krenn and protruding beyond the basal part of the prementum. Kristensen, 2000). Compressing the sides of the prementum together is Intake region. Closed suctorial proboscides require probably not sufficient to eject the looped glossa. It is specialized regions at the apex of the food canal for fluid astonishing that the labial musculature in the examined uptake. In pollen wasps, this takes place through the slit-like species of the subtribe Masarina, e.g. Ceramius, is only openings in the food canal of the glossal lobes. In other slightly modified from the plesiomorphic condition in insects the apical regions of the food canal are outfitted with pollen wasps; all muscles can be readily homologized specialized sensilla, for example in Lepidoptera (Krenn, with those in other Vespinae and in general with other 1998; Krenn and Kristensen, 2000; Krenn et al., 2001) and Hymenoptera (Duncan, 1939; Matsuda, 1965). Compared to Diptera (Szucsich and Krenn, 2000, 2002). However, in the short-tongued Masarinae, e.g. Paragia, only one muscle pollen wasps, the acroglossal button and its sensillae are not has modified its course. Due to the elongation of attachment strongly modified even in the most derived species. sites on the anterior lingual plate and the particularly arched The long of bees has different requirements. The prementum, one part of this muscle is positioned up to 908 glossa is enclosed inside the food tube and independently differently from the plesiomorphic condition. In the derived performs licking movements extending beyond the condition the contraction of this muscle compresses the ensheathing tube (Snodgrass, 1956; Harder, 1982; Plant, glossal pouch inward and seems to be the major force in personal observation). The apical food tube must first be initiating extension of the glossa, at least in Ceramius. In the loaded with nectar by means of the glossal movements and plesiomorphic condition, the same muscle functions for capillary action, before it is drawn through the food tube to extension as well, thus no new neural motor pattern is the mouth by suction action (Kingsolver and Daniel, 1995). necessary for the control of the glossa movements. A presuction nectar-loading stage is not necessary in butterflies and the higher pollen wasps, since suction begins 4.2. Comparative remarks on proboscis evolution in with immersion of the apical uptake region in the nectar. Hymenoptera Mechanisms of protraction and retraction. The labio- maxillary complex of aculeate Hymenoptera permits a of an elongated proboscis associ- slight extension and retraction. The mechanisms for this ated with flower visiting behavior is apparent in many have been described for Vespula (Duncan, 1939), sphecids groups of Hymenoptera. Even within the Masarinae a (Ulrich, 1924), scoliids (Osten, 1982, 1988), and the short- second clade, the Australian Metaparagia independently tongued bee Andrena (Harder, 1983). It involves at least evolved an elongated glossa for probing flowers with deep three major steps, the movement of the cardines which corollas (especially Goodeniaceae; Gess et al., 1995; Gess, swing the proboscis in or out of the proboscidial fossa, the 1996). However, in this taxon the proximal section of the z-shaped fold between prementum and glossa, and the glossa is greatly elongated and the paraglossae reach to the folding or unfolding of the galea. When a significant bifurcated section of the glossa; in addition the proboscis is elongation of apical parts of the proboscis takes place, new also retractable into the prementum (Carpenter, 1996/1997) steps of extension and retraction are added onto the but the associated morphological changes and the mechan- preexisting ones. ism of retraction are undetermined. Storage of glossa. The length of the proboscis is Examples of long or moderately long mouthparts are contingent on its required storage space as well as the numerous in other aculeate Hymenoptera, i.e. Eumeninae retraction method; in the pollen wasps, e.g. Ceramius, the (Vespidae), e.g. species of Eumenes, Pterocheilus, Raphi- space available inside the prementum is a limiting factor for glossa, Labochilus (Schremmer, 1961; Richards, 1962; the length of the glossa. One solution taken by the higher Bohart and Stange, 1965; Giordani Soika, 1974; Haeseler, Masarina is to store the glossa outside the prementum by 1975; Osten, 1982; Mauss, personal observation), many creating an ‘opening’ in the cuticular membrane between Sphecinae including Ammophila, , some Bembicinae the cardines through which the glossa invaginates into a (Ulrich, 1924; Bohart and Menke, 1976; Osten, 1982), large sac. The basic mechanism, however, remains the same certain Tiphiidae, Sapygidae, and Scoliinae (Osten, 1982, as in Ceramius, in that the glossa is retracted into one loop 1991) and some Chrysididae and Pompilidae (Jervis, 1998). even if it is so large as to protrude out of the prementum. Most of these derived elongate mouthparts differ from that Quartinioides has taken another direction, its glossa lies in Masarinae in that the food canal is not formed exclusively entirely within the prementum but in several irregular criss- by the glossa but includes other parts of the labium and crossing loops. The mechanism of extension in Quarti- maxillae. For example, in the long-tongued bees ( nioides, however, remains puzzling. It may be significant and Megachilidae) the elongate and flattened labial palpi that its glossa, although very long, is also extremely thin, at together with the galea form a stationary sheath-like tube least in the species examined. Richards (1962) suggested within which the glossa operates (Snodgrass, 1956). that hemolymph pressure was important for extension. It is Retraction of the glossa into the prementum as in the likewise not known how the glossa of Celonites and Masarina is not unique in Hymenoptera. It has been Jugurtia is projected out from its fully retracted position described for Scolia (Scoliidae) (Ko¨nigsmann, 1976; H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 117

Table 3 Composition of food canal produced by elongation of apical mouthparts in various aculeate Hymenoptera. Type of mouthpart specializations (CNEA, see text) follows Jervis (1998)

Glossa Paraglossa Galea Labial Maxill. palpi palpi

Masarinae þ Metaparagia and subtribe Masarina Eumeninae þþ Raphiglossa (CNEA type 1) Eumeninae þþ þ ? Eumenes (Osten, 1982) Scoliidae þþ Scolia (Osten, 1982) Chrysididae þ Parnopes (Linsenmaier, 1997) Sphecinae þþ Ammophila (Ulrich, 1924) (CNEA type 1) Sphecinae þþ þ Bembix Long-tongued þþþMegachilidae, Apidae (CNEA type 4) bees þþþProtomeliturgini, Melitturgini, Perditini (e.g. Perdita ), Calliopsini (e.g. Callonychium ), Andrena (Callandrena ) micheneriana (LaBerge, 1978) (CNEA type 4) Andrenidae þþNeffapis longilingua () (Rozen and Ruz, 1995) (CNEA type 6) þþþþVarious Rophitinae Halictidae þ Ariphanarthra palpalis (Eickwort, 1969) (CNEA type 5) þþ Leioproctus (Filiglossa ) filamentosus (Michener 2000) Colletidae þ Niltonia (Colletinae) (Laroca et al., 1989) Colletidae þ Chilimelissaa, Xeromelissa (Xeromelissinae), species of Hylaeus (Pseudhylaeus ), H.(Prosopisteroides ) (Hylaeinae), Euhesma, and Euryglossa tubulifera (Euryglossinae) (Michener, 1965; Houston, 1983) (CNEA type 5) Colletidae þ Palaeorhiza papuana (males only) (Michener, 1965) Andrenidae þ Oxaeidae, Andrena (Iomelissa ) violae (Michener, 1944), A.(Charitandrena ) hattorfiana, A.(Taenandrena ) lathyri þ Pseudophilanthus tsavoensis (Michener, 1981,asAgemmonia )

a Incorrectly given as labial palpi in Laroca et al. (1989).

Micha, 1927; Osten, 1982, 1988) and Epomidiopteron structures for evolutionary recruitment. In some cases it (Tiphiidae) (Osten, 1991). However, the proboscis at least in may be possible to indicate which structures are preoccu- Scolia is not a thin suctorial tube as both the glossa and pied, for example, in pollen wasps the galea is connected paraglossae are enlarged and fold back into the prementum with pollen eating and therefore presumably not available (Osten, 1982). In long-tongued bees, the elongated apical for elongation. However, in general it is difficult to parts of the proboscis fold back beneath the prementum. determine why one particular structure or one set of Depending on the total glossal length the folded proboscis structures undergoes modification and not another. may exceed the thorax and abdomen. To summarize, at least three morphological–functional Some short-tongued bees have independently evolved an groups of mouthparts can be distinguished which may be elongate proboscis of very similar construction to that in related to feeding habits of adult Hymenoptera. (1) The Apidae and Megachilidae, for example, especially in unspecialized small labiomaxillary complex. (2) Apo- Rophitinae (Halictidae) and Panurginae (Andrenidae) morphic ‘short-tongued’ and (3) Apomorphic elongate or (Michener, 1944, 2000), and also in one species of Andrena ‘long-tongued’. (Andreninae) (LaBerge, 1978). Individual species of short- The first group is presumably plesiomorphic for tongued bees have also achieved other forms of elongation, Hymenoptera (Jervis, 1998).Themainbodyofthe presumably with formation of a food canal, by production of mouthparts usually does not extend beyond the reach of the maxillary palpi, or the labial palpi, or both together. the open mandibles. The labial and maxillary palpi, Elongation of the glossa alone is also occasionally found in however, are very long and active in performing tactile short-tongued bees, however, it is not apparent how or if a sensory movements. The mouthparts are used to lick and special food tube is formed. The structures which constitute suck nectar, honeydew or prey body-fluid, examples are the elongated section of the apical food canal are listed for Syspasis (Ichneumonidae) (Richards, 1977), Ampulex various bees and other aculeate Hymenoptera in Table 3. (Ulrich, 1924) and Psenulus (). It is reasonable to assume that the structures of the Modifications of the plesiomorphic condition have led to maxillae and the labium underlie different selection development of short and long-tongued conditions which pressures and evolutionary constraints arising from their are associated with nectar feeding. The short-tongued role in foreleg cleaning, nectar feeding, pollen ingestion, proboscis as in many bees and wasps can extend somewhat nest and brood cell construction and other functions of the beyond the reach of the open mandibles since it has proboscis. A change in one of these behaviors may free undergone a general increase in size or length of its major 118 H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 parts. These parts of the labiomaxillary complex involve the Furthermore, the mouthpart condition found in typical basal section (cardo, hypopharynx, labrum), the mid-section short-tongued bees such as Hylaeus, Colletes, Andrena and (stipes, subgalea, laciniae, prementum) and not merely the Melitta, does not generally permit these insects to utilize apical section (glossa, paraglossa, labial and maxillary concealed nectar sources. The basal taxa of the Masarinae palpi, postpalpal galea). The short-tongued mouthparts are with short mouthparts are likewise restricted to plant species thus well developed compared to the plesiomorphic small with easily accessible, actinomorphic flowers, e.g. Prisco- proboscis. The principles of proboscis extension, retraction masaris on Molluginaceae and Aizoaceae (Gess 2001), and formation of the food canal are similar to those of the Paragia on Myrtaceae, Proteaceae, Mimosaceae and plesiomorphic small proboscis, however, morphological Bromeliaceae (Houston, 1984, 1986; Snelling, 1986; Gess, differentiation may occur in the postmental region (Plant 1996). Our field observations on flower visiting behavior and Paulus, 1987), shape of the glossa, articulation of the confirm that species of Ceramius with elongate mouthparts base of the glossa, and a reduction in the relative length and are able to utilize derived flower types with concealed function of the maxillary and labial palpi. nectaries (e.g. Fabaceae, Lamiaceae, Pontederiaceae; An elongate proboscis may be defined, as in the reviewed by Gess and Gess (1989), Gess (1996), Mauss Megachilidae and Apidae, when the glossa exceeds the (1996), Mauss and Mu¨ller (2000) and Garcete-Barrett and length of the prementum (Harder, 1983). An apical Carpenter (2000)) while the relatively short-tongued elongation can occur by other structures as well. Essential Ceramius fonscolombei visits flowers with readily access- for the discussion here is when these lengthenings ible nectar. necessitate the addition of new construction designs and The morphology of the proboscis and its mechanisms of morphological innovations with respect to food canal extension in Ceramius permit a rapid exploitation of flowers formation, storage of elongated parts, mechanisms of with very narrow corolla tubes. Pollen wasps can extend extension and retraction, etc. their proboscis into a narrow corolla tube after landing on Jervis (1998) and Jervis and Vilhelmsen (2000) docu- the flower since the glossa is propelled forward from the mented eight types of mouthpart elongations in Hymeno- looped resting position. In contrast, the long proboscis of ptera for the uptake of nectar from flowers with long, bees requires more space to swivel out and unfold into the narrow, tubular corollas and referred to them as CNEA feeding position. Many long-tongued bees must unfold their (concealed nectar extraction apparatus). Briefly stated, these proboscis before insertion into flowers and those with a are: (1) glossa and galea elongate, (2) glossa elongate and particularly long proboscis, such as euglossids and Antho- galea only moderately elongate, (3) glossa, galea and phora, hover in front of blossoms and approach flowers with maxillary palpi elongate, (4) glossa, galea and labial palpi an extended proboscis. elongate, (5) maxillary palpi elongate, (6) glossa and labial Based on the proposed phylogeny and biogeographic palpi elongate, (7) maxillary and labial palpi elongate, (8) pattern of the pollen wasps it is possible to roughly estimate prementum and stipes elongate. These types were intended when the evolution from licking/sucking mouthparts to a to account for the surprising variation found in various pure suctorial proboscis should have occurred (Fig. 20). The groups of symphytans and parasitoid Apocrita. basal subfamilies of the Vespidae, including the Masarinae, We list in Table 3 those structures which partake in the appear to have become established in the early to middle elongation of the apical food canal for various bees and Cretaceous (Grimaldi, 1999). The basal-most group of other aculeate Hymenoptera. Some of these examples pollen wasps, Gayellini, is limited to the Neotropics. The correspond to CNEA types of Jervis (1998) and are Masarini, however, represent a typical disjunct Gondwanan indicated in the table, others would constitute new types distribution with the Paragiina endemic in the Australian of CNEA, e.g. the mouthpart elongation of the higher region and Masarina restricted to the remaining areas (Gess, Masarinae, since it is achieved only by the glossa. 1992; Carpenter, 1993). In addition, most genera of It can be seen that major aspects of the functional Masarinae are highly endemic to continental areas. The morphology between the plesiomorphic small mouthparts diversification of pollen wasps probably thus took place and the apomorphic short-tongued condition are similar. We after the middle of the Cretaceous and coincided with the seek to underscore the functional–morphological differ- diversification of angiosperms (Crane, 1993; Grimaldi, ences between short-tongued and elongated proboscides and 1999). The independent evolution of an elongated proboscis to point out the morphological consequences of elongation, in the stem-groups of the subtribe Masarina and Meta- rather than to emphasize the lengths of the different parts. paragia (Paragiina) must have occurred after separation of Thus we would not include in Jervis’ (1998) CNEA type 1 the Australian land mass in the middle Cretaceous, about most of those flower visiting bees and wasps with 100 million years ago (Fukarek, 1995). mouthparts that have undergone a slight or moderate or short elongation. These forms correspond to our group 2, apomorphic short. A short-tongued condition probably Acknowledgements represents the evolutionary starting point for further modification by elongation. We are especially grateful to J. Carpenter (New York) H.W. Krenn et al. / Arthropod Structure & Development 31 (2002) 103–120 119 and F. Gess and S. Gess (Grahamstown) who kindly Gess, S.K., 1996. The Pollen Wasps—Ecology and Natural History of the collected some of the investigated material for us and to Masarinae, Harvard University Press, Cambridge, MA, 340 pp. L. Castro (Teruel) for his extraordinary hospitality and Gess, F.W., 1998. P. namibiensis Gess, a new genus and species of Masarinae (Hymenoptera: Vespidae) from Namibia, southern Africa, indispensable support of V. Mauss during the field studies. with a discussion of its position within the subfamily. Journal of M. Lo´pez (Diputacion General de Aragon) kindly issued Hymenoptera Research 7, 296–304. the required collection permits. 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