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Micron 42 (2011) 498–505

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Micron

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unctional morphology of the mouthparts in the scorpionfly Sinopanorpa tinctaMecoptera: Panorpidae)

ing Huang, Baozhen Hua ∗

ey Laboratory of Plant Protection Resources and Pest Management, Ministry of Education, Northwest A & F University, Yangling, Shaanxi 712100, China

r t i c l e i n f o

rticle history:eceived 27 July 2010eceived in revised form 27 January 2011ccepted 29 January 2011

eywords:nsectainopanorpaouthpartsorphology

a b s t r a c t

The feeding mechanism of insects can be deduced from the morphology of their mouthparts. The mouth-part morphology of the scorpionfly Sinopanorpa tincta (Navás) was investigated using light and scanningelectron microscopy. The mandibulate mouthparts of S. tincta are situated at the distal end of the rostrum,which is formed from the elongation of clypeus and subgenae. The blade-shaped mandible terminatesin two inwardly curved sharp teeth. The paired maxillae each consist of a triangular cardo, an elonga-ted stipes, a hirsute galea, a spiny lacinia, and a five-segmented palpus. Rows-arranged claw-like spinesare first found to occur on the mesal side of the lacinia. The labium is composed of a basal elongatedmembranous submentum, a central vase-shaped mentum, and a short distal prementum, which dista-lly carries a pair of two-segmented labial palpi. The proximal labial palpomere is very hirsute on mesal

ensillumeeding

side and well sclerotized at the basal part of the lateral side. On the baso-mesal side of the distal labialpalpomere is a triangular area, which is densely furnished with long microtrichia. Various sensilla areconcentrated on the epipharynx, maxillary and labial palpi. The pattern of thick basiconic sensilla at theapex of epipharynx exhibits distinct sexual dimorphism. The feeding mechanism is conjectured from theultramorphology of the mouthparts. We suggest that scorpionflies are likely to feed on liquid food of

l digeserve

their prey after extra-oraand hypopharynx might

. Introduction

Mouthparts are the feeding apparatus of insects, involved inrocessing and manipulating food items (Chapman, 1998, 2003;nodgrass, 1935). Although two basic types of mouthparts can beategorized in insects, one adapted for biting and chewing solidood, and the other adapted for sucking up liquids (Chapman, 1998),4 fundamental mouthpart classes were recognized among extant

nsects by Labandeira (1997). According to fossil record, compa-ative morphology and embryogenesis, mandibulate mouthpartsre the most generalized form from which other types of mouth-arts evolved (Ross et al., 1982). During the evolution of insects,he mouthparts have been modified in various groups to performhe ingestion of different types of food and by different feedingtrategies. In general, insects with mandibulate mouthparts feedpon solid food, while those with sucking mouthparts are modi-

ed to form a tube through which fluid is sucked up into thesophagus (Chapman, 1998). Research on mouthpart morphologyould provide insight on the feeding mechanism of insects (Krenn,007). The morphology of insect mouthparts has become one of

∗ Corresponding author. Tel.: +86 29 87091342; fax: +86 29 87091342.E-mail addresses: huangjing@nwsuaf.edu.cn (J. Huang),

uabzh@nwsuaf.edu.cn (B. Hua).

968-4328/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.oi:10.1016/j.micron.2011.01.011

stion. Hair brushes on the hirsute epipharynx, galeae, laciniae, labial palpi,to filtrate large particles.

© 2011 Elsevier Ltd. All rights reserved.

the most intensively examined and abundantly documented struc-tures among animals (Labandeira, 1997), especially in the Diptera(Coronado-Gonzalez et al., 2008; Tinkeu and Hance, 1998), Ephe-meroptera (Baptista et al., 2006; Polegatto and Froehlich, 2001),Coleoptera (Anton and Beutel, 2006; Betz et al., 2003; Beutelet al., 2001), Lepidoptera (Büttiker et al., 1996), and flower-visitinginsects (Karolyi et al., 2009; Krenn et al., 2005). In Mecoptera, howe-ver, the functional morphology of the mouthparts has not been welldocumented hitherto.

Mecoptera is one of the basal lineages in the endopterygoteinsects, and this is primarily based on larvae having a pair of com-pound eyes on the head and the fossil record. Panorpidae, themost speciose family in Mecoptera, are commonly called scorpion-flies because the genital bulb (the ninth abdominal segment) ofmales is enlarged and recurved backwards like the stinger of ascorpion. As saprophagous insects, adult scorpionflies mainly con-sume soft-bodied dead arthropods (mainly insects) as their primaryfood source (Byers and Thornhill, 1983). In spite of possessingmandibulate mouthparts, scorpionflies were hypothesized to besucking insects after observations were made of their feeding habit

(Nakahara, 1922). However, a thorough understanding of their fee-ding approach is still unclear.

Early research on the mouthparts in Panorpidae was mainlylimited to general morphology (Crampton, 1921; Ferris and Rees,1939; Hepburn, 1969b; Imms, 1944; Issiki, 1933; Miyaké, 1913;

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tanes, 1922) although some detailed descriptions of the mouth-arts have been well documented in the European Panorpaommunis by Steiner (1930) and Heddergott (1938) through lighticroscopy observation. Recently, detailed mouthpart structuresere investigated in Boreidae (Beutel et al., 2008) and Nannocho-

istidae (Beutel and Baum, 2008; Beutel et al., 2009). However, theltramorphology of the mouthparts in Panorpidae has not been stu-ied to date. Herein, we investigated the functional morphology ofhe mouthparts of the scorpionfly Sinopanorpa tincta (Navás, 1931),hich was transferred from the genus Panorpa Linnaeus by Cai et al.

2008), using light and scanning electron microscopy.

. Materials and methods

Adults of S. tincta (Navás, 1931) were collected from theaibaishan National Nature Reserve (107◦42′E, 34◦05′N, 1250 m)n the Qinling Mountains, Shaanxi Province, central China in

id-July 2009, and were preserved in 70% ethanol at 4 ◦C.The mouthparts were dissected in 70% ethanol under a Nikon

MZ1500 microscope. Photos were taken with a QImaging Retica000R CCD digital camera attached to the microscope and thenurther treated with the software Auto-Montage Pro.

The specimens used for scanning electron microscopy observa-ion were ultrasonically cleaned for two minutes, dehydrated in araded ethanol series, dried in a critical point drier, sputter-coatedith gold, examined and photographed under a JEOL JSM-6360 LV

canning electron microscope at 15 kV.

. Results

.1. Gross morphology of the mouthparts

In adult S. tincta, the clypeus and subgenae are conspicuouslyrolonged into a rostrum (Figs. 1C and 2A). The maxillary stipitesnd labial submentum are correspondingly prolonged, lying in antherwise membranous posterior wall of the rostrum; other partsf the mouthparts are not particularly elongated.

The frontoclypeal suture is not recognizable, its existenceeing indicated only by a pair of prominent anterior tentorialits (Fig. 1A). The proximal elongated region is the clypeus, for-ing the anterior wall of the rostrum. The terminal triangular

rea is the labrum, weakly differentiated from the clypeus bywo lateral constrictions. The epipharynx is on the inner side ofhe labrum (Fig. 3A). The mandibles are blade-shaped (Fig. 5A),mmediately behind the labrum. Posterior to the mandibles lie theaired maxillae (Fig. 5C), each of which consists of a basal scle-otized cardo and an elongated stipes which is connected withhe inner lacinia, the outer galea and the well-developed five-egmented maxillary palpus. The labium forms the posterior wallf the rostrum (Figs. 1C and 2A), comprising the proximal post-entum, which is subdivided into a submentum and a mentum,

nd the distal prementum, which bears a pair of two-segmentedabial palpi.

.2. The labrum

The triangular labrum is difficult to differentiate distinctly fromhe clypeus. The clypeolabral suture seems to have vanished, remai-ing only as deep lateral constrictions, which divide the wholerea into a labrum and a clypeus on the lateral margin (Fig. 1B).

he labrum is highly chitinized and strongly convex mesally, bea-ing several setae at the base and 22 bristles on each lateral edgeFig. 1B). There are also a number of setae on the surface of the well-eveloped clypeus, most on the lateral sides, seldom in the middleFig. 1A).

42 (2011) 498–505 499

3.3. The epipharynx

The epipharynx is membranous and is characterized with twonotches at lateral edges, the distal one at the apical third and theproximal one at the basal 1/5 (Fig. 3A).

On the apex of the epipharynx is located a triangular patch ofthick basiconic sensilla (type I) (Figs. 3A and 4), all of which havenumerous longitudinal grooves and are 15.31 �m long with a basaldiameter of 8.51 �m. The number of these sensilla ranges from23–28 in males to 38–47 in females. Their pattern also exhibitsdistinct sexual dimorphism (Fig. 4), three rows in males and sevenin females. The lateral margin of the epipharynx bears a stiff bristlebrush from the apex to the distal notch (Fig. 3A), and long furcatedhair (microtrichium) brushes between the two notches (Fig. 3B).

Palmate sensilla (type I) are present on the distal third of theepipharynx at random (Fig. 3C). At high magnification, it is evidentthat each of these sensilla is situated in a shallow socket and is fur-cated at the tip. A mid band of sensilla extends from the subapexto the centre, consisting of basiconic (type II) and palmate sensilla(type II), differing in structure and distribution (Fig. 3A and C). Twopalmate sensilla II are present at each end of the band, with irre-gular apices. Sixteen basiconic sensilla II are situated in the middle(Fig. 3C), their socket with a triangular process (Fig. 3D). Two late-ral bands of sensilla are in an open V-shape on the basal half of theepipharynx, each consisting of two irregular rows (Fig. 3A): onewith 15 basiconic sensilla (type II) of 8.66 �m long on average, theother with 24 chaetic sensilla (type I) of 5.41 �m long (Fig. 3F). Bet-ween the two lateral bands are numerous microtrichia formed bycuticular extensions (Fig. 3D). An auriform area is produced basal tothe proximal notch (Fig. 3A), bearing bundles of long microtrichiaand 17 basiconic sensilla (type III) on each side (Fig. 3E). These basi-conic sensilla differ from the aforementioned two types by beingsmaller and shorter with flattened sockets.

3.4. The mandibles

The highly sclerotized mandibles are flattened, elongated, andslender with smooth surface (Fig. 5A), 148.5–150.5 �m wide and642–648 �m long (measured from the tip to the hypocondyle). Theleft and right mandibles seem roughly to be symmetrical. Theymirror each other at a distance and swing transversely, constitutinga structure for piercing. When the process of piercing is accom-plished, they will interpose into the area between the galeae andlaciniae after crossing opposingly (Fig. 2A). The mandibular apexterminates in two inwardly curved sharp teeth, with the outer toothdistinctly longer than the inner one (Fig. 5A). The basal areas of thetwo teeth partly overlap.

3.5. The maxillae

The paired maxillae arise from the postgenal bridge, each con-sisting of a cardo, a stipes, a lacinia, a galea, and a palpus (Fig. 1C).The basal cardo is a triangular sclerite. The slender, elongated sti-pes is recognizable on the posterior side of the rostrum, comprisingpart of the elongated rostrum. Distally on the stipes are two lobes,an outer galea and an inner lacinia. The galea and lacinia toget-her form a U-shaped structure with the latter slightly longer. Morelaterally on the stipes is a well-developed, five-segmented maxi-llary palpus (Fig. 2D), which is inserted on a membranous palpifer(Figs. 2D and 6B). Maxillary palpomere I is slightly longer than II.Palpomere III is twice as long as II. Palpomeres IV and V are equal

in length, and slightly longer than palpomere I.

The cardo bears eight setae, two of which are 96–108 �m longand the remaining shorter than 39 �m. On the stipes is a row ofsetae of 132.6 �m long along its whole length (Figs. 1C and 2A).Long microtrichia formed from cuticular extensions (Fig. 6E) are

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500 J. Huang, B. Hua / Micron 42 (2011) 498–505

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ig. 1. Mouthparts of Sinopanorpa tincta, male. (A) Clypeus and labrum in frontallypeus and labrum and (C) mouthparts in posterior view. atp, anterior tentorial pid, mandible; mp, maxillary palpus; pm, prementum; ppf, palpifer; ppg, palpiger;

resent on the mesal side and apices of the galea and lacinia, andre in clusters (Fig. 6A and B). A patch of campaniform sensillas present near the fused base of the lacinia and galea (Fig. 6G).law-like spines occur on the mesal side of the lacinia and are arran-ed regularly in nine rows, each of which has eight spines (Fig. 6Bnd F). In front of the spines is an array of dense long fine micro-richia in a comb-like pattern (Fig. 6E). Campaniform sensilla areresent on the lacinia (Fig. 6F). Each sensillum consists of a domedap hinged to a surrounding ring of raised cuticle. On the maxi-lary palpus, Böhm’s bristles are present at the base of the first andecond segments on the lateral side (Fig. 6B and D). No sensillum

as observed on palpomere I in posterior view, but many campa-iform and chaetic sensilla (type II) were found on palpomeres II–VFig. 6B and D). In frontal view, palpomeres I–IV only bear chaeticensilla (type II), ranging from 22.6 to 117 �m in length (Fig. 6A).t is unique that on the distal palpomere two types of basiconic

ig. 2. Mouthparts of male Sinopanorpa tincta in posterior view. (A) Mouthparts; (B) epipaxilla. ap, anterior pharynx; cd, cardo; epi, epipharynx; gl, galea; lc, lacinia; lp, labial pa

nd II; pm, prementum; ppf, palpifer; ppg, palpiger; sm, submentum and st, stipes. Scale

(B) apical part of the head in frontal view, arrow shows the constriction betweencardo; cly, clypeus; gl, galea; lbr, labrum; lc, lacinia; lp, labial palpus; m, mentum;bmentum and st, stipes. Scale bars: A and C = 500 �m and B = 200 �m.

sensilla (types IV and V) were found. Two groups of short basi-conic sensilla (type VI) occur on the apex of the distal palpomere(Fig. 6C).

3.6. The labium

The labium constitutes part of the posterior wall of the elongatedrostrum (Fig. 1C). The postmentum is subdivided into a proximalsubmentum and a distal mentum. The submentum is prolonged andmembranous, occupying the area between the cardines and stipi-tes of the paired maxillae. The mentum is sclerotized and inverted

vase-shaped. The chitinized prementum terminally bears a pair oftwo-segmented labial palpi, each of which is inserted in a mem-branous palpiger. The basal labial palpomere is much broader andlonger than the heavily sclerotized distal one (Figs. 2C and 7A).Glossae and paraglossae are absent.

harynx and clypeus, showing the mouth (arrow); (C) distal labium and (D) the leftlpus; m, mentum; md, mandible; mp, maxillary palpus; pl1–2, labial palpomeres Ibars: A and B = 200 �m; C and D = 100 �m.

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J. Huang, B. Hua / Micron 42 (2011) 498–505 501

Fig. 3. Epipharynx of Sinopanorpa tincta, male. (A) Habitus, black arrow shows the distal notch; white arrow shows the proximal notch, inset is a magnification of thel wing te n of thm III; CSF

ltadmadTnsssBdlscbaswo

ong furcate microtrichia on the epipharyngeal edge; (B) magnification of (A), shopipharynx, inset shows a magnification of palmate sensillum I; (D) magnificatioid-basal part of epipharynx of (A). Aa, auriform areas; BS1–3, basiconic sensilla I–

= 50 �m; C = 20 �m; D and E = 10 �m.

The glabrous submentum and mentum are devoid of sensi-la. A group of campaniform sensilla are borne on each side ofhe prementum (not shown). Two pairs of extremely long bristlesre situated at the apex of each side of the prementum, exten-ing almost to the middle of the basal palpomere (Fig. 7A). Theesal pair is about 340 �m long and the lateral pair 390 �m on

verage. In frontal view, the whole prementum and palpiger areensely furnished with microtrichia directed downward (Fig. 7B).he basal labial palpomere is mostly fleshy in texture, being fur-ished with dense furcated microtrichia and numerous basiconicensilla (type IV) amid on the mesal side, and seems to be compo-ed of three subsegments on the lateral side (Fig. 7C). The basalubsegment is sclerotized and the longest, being provided withöhm’s bristles (nine short macrosetae) laterally at the base, abun-ant campaniform sensilla at the basal half (Fig. 7C) and eight

ong bristles at the apex. The two inner-most bristles are quitehort, but the other six are considerably long, some almost rea-hing the apex of palpomere I. From inner to outer, these eight

ristles are 77.15, 90.41, 130.90, 183.50, 171.20, 200.47, 141.00,nd 140.30 �m long, respectively. The second subsegment is thehortest and glabrous on the lateral side. The distal subsegment isholly furnished with dense short microtrichia. On the mesal side

f palpomere II is a basal triangular area, on which long microtrichia

he mid-left edge of epipharynx, arrow shows the distal notch; (C) middle part ofe basal part of (C); (E) auriform area of epipharynx and (F) magnification of the1, chaetic sensilla I; PS1–2, palmate sensilla I and II. Scale bars: A = 100 �m; B and

are densely situated (Fig. 7B and F). On the lateral side of palpo-mere II are situated many basiconic sensilla (type IV) of 88–166 �mlong and campaniform sensilla (Fig. 7E), and on the mesal side areborne several basiconic sensilla (types IV and V) (Fig. 7F). On theapex of the distal palpomere are situated two groups of short basi-conic sensilla (type VI) similar to those on the maxillary palpus(Fig. 7F).

3.7. The hypopharynx

The hypopharynx is a tongue-like structure, its apex and surfacebeing densely covered with long furcated microtrichia (Fig. 5B), andlateral sides glabrous. At the base of the hypopharynx, where itjoins the labium, is situated the orifice of the salivary duct (Fig. 5C).Around the orifice are many palm-like spines, each of which bearssix micro-spines (Fig. 5D).

4. Discussion

Mandibulate mouthparts generally have developed and asym-metrical mandibles, which are often differentiated into a moredistal incisor region and a proximal molar region whose develop-ment varies with the diet of insects (Chapman, 1998). In Mecoptera,

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ig. 4. Apical part of epipharynx in Sinopanorpa tincta, showing the pattern of ba= 100 �m and D = 50 �m.

he mandible possesses a well-developed apical and two distinctubapical teeth, and a basal molar part in Caurinus in BoreidaeBeutel et al., 2008), but bears a flattened and unsclerotized dis-al part and a shallow concavity on the lateral margin at the base inannochoristidae (Beutel and Baum, 2008). In Panorpa, the mandi-

le is flattened and parallel-sided, and terminates in two or threeeeth (Issiki, 1933; Otanes, 1922). The mandibles of Sinopanorpa arelongated, blade-shaped and almost symmetrical, with two promi-ent apical teeth (equivalent to the incisor) but with molar partbsent.

ig. 5. Mouthparts of male Sinopanorpa tincta in posterior view. (A) Mouthparts with maxrrow shows the orifice of salivary duct and (D) magnification of the orifice (arrow) of saandible; mp, maxillary palpus; ppf, palpifer; sd, salivary duct and st, stipes. Scale bars:

ic sensilla I. (A) and (C) males; (B) and (D) females. Scale bars: A and C = 20 �m;

There is a long-standing controversy as to whether the two lobesof the stipes are lacinia and galea or merely galea in the mouth-parts of Panorpidae. Issiki (1933) and Otanes (1922) considered thatthe lacinia is absent or reduced, and the galea is subdivided intotwo lobes; while Heddergott (1938), Miyaké (1913), and Steiner

(1930) regarded the inner lobe as lacinia. Imms (1944) further con-firmed this conclusion by dissecting the musculature of maxillaein Panorpidae. Based on our investigation (Fig. 6A), there exists adistinct demarcation between the lacinia and galea, confirming thepresence of lacinia in Panorpidae.

illae and labium removed; (B) hypopharynx; (C) mouthparts with labium removed,livary duct in (C). gl, galea; hcd, hypocondylus; hyp, hypopharynx; lc, lacinia; md,A = 100 �m; B and D = 50 �m and C = 200 �m.

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J. Huang, B. Hua / Micron 42 (2011) 498–505 503

Fig. 6. Maxillae of Sinopanorpa tincta. (A) Frontal view of the right maxilla in male; (B) posterior view of the left maxilla in male; (C) apex of the distal palpomere in male;( headl s andB ensillD

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D) posterior view of palpomere II in male, showing the campaniform sensilla (arrowacinia in male, showing the campaniform sensilla (arrowhead) and claw-like spineöhm’s bristles; BS4–6, basiconic sensilla IV–VI; ClS, claw-like spines; CS2, chaetic s= 20 �m; E and G = 50 �m and F = 10 �m.

Various views also exist on the labial structure in Panorpidae,specially with respect to the region between the labial palpusnd submentum. Miyaké (1913), Crampton (1921), and Steiner1930) considered that the vase-like area is mentum and the regionetween the mentum and palpus is the palpiger. Otanes (1922)egarded the long membranous area and the sclerotized vase-likeegion as submentum. He termed the distal fused prementum, pal-igers, glossae, and paraglossae as a mecaglossa. Ferris and Rees1939) believed that the palpiger sensu Crampton (1921) is separa-ed into a prementum and palpiger, although not very obvious. Weo not want to consider these arguments further here, suffice it toay that the sclerotized vase-shaped plate connected with submen-um is the mentum, distal to which is the prementum and triangularalpiger successively. The boundary between the prementum andalpiger is not well-defined. However, on the prementum therexist two long bristles, which we treated as a landmark of the apexf the prementum. This is in accord with Issiki (1933), Heddergott1938), and Imms (1944).

The sensilla on mouthparts are mainly contact chemoreceptorso taste food (Zacharuk, 1985), serving the functions of olfactionnd gustation as well as mechanosensation (Blaney and Chapman,969; Chapman, 2003; Prakash et al., 1995; Spiegel et al., 2005).arious sensilla on the epipharynx were presumed to serve the

s); (E) magnification of the galea and lacinia in (A); (F) posterior view of part of the(G) apex of stipes in female, showing the campaniform sensilla (arrowheads). BB,

a II; gl, galea; lc, lacinia and ppf, palpifer. Scale bars: A = 200 �m; B = 100 �m; C and

taste function of insects (Faucheux, 1995; Grell, 1938; Heddergott,1938). Several kinds of sensilla were found on the mouthparts ofS. tincta, including basiconic, chaetic, palmate, and campaniformsensilla. On the apex of epipharynx, a pattern of basiconic sensilla(type I) with longitudinal grooves was found in Sinopanorpa (Fig. 4),in contrast to other panorpid genera whose basiconic sensilla havea smooth surface and only 4–8 in number (Huang J., unpublisheddata). The palmate sensilla II have not been described previously,being present only on the two ends of the mid band on the epip-harynx. Campaniform sensilla perceive cuticular stresses resultingfrom mechanical deformation (McIver and Siemicki, 1975). Sensillavary on the maxillary and labial palpi in different orders. In Blatta-ria (Blattellidae), the distal half of the terminal maxillary palpomerebears groove-slit sensilla and the terminal segment of labial palpusare mainly furnished with trichoid and chaetic sensilla in clusters(Bland et al., 1998). In Diptera (Psychodidae), the maxillary palpiand labella are densely covered with trichoid sensilla, which mayfunction as chemo- and mechanoreceptors (Spiegel et al., 2005).

Based on our observations, two groups of basiconic sensilla arepresent on the apex of the maxillary and labial palpi in Panorpidae.

The mouthparts of insects which feed on fluids are modified invarious ways to form a tube through which liquid can be drawn intothe mouth. But some predaceous larvae that feed on the body fluids

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ig. 7. Labium of Sinopanorpa tincta, female. (A) Posterior view of the distal labium; (f palpomere I; (E) lateral side of palpomere II and (F) mesal side of palpomere II. Band II; pm, prementum; ppg, palpiger; arrowheads, campaniform sensilla. Scale b

f their prey have mandibulate mouthparts, the mandibles of whichesemble those of insects feeding on solid food. In general, the fee-ing mechanism of the Mecoptera has not been elucidated clearly

n many groups. In Nannochoristidae, adults were supposed to feedn liquid substance deduced from the discovery of a food channelormed by the distal part of the labrum and mandibles (Beutel andaum, 2008). The saprophagous Panorpidae feed upon soft-bodiedead or dying arthropods (mainly insects), and rarely on heavilyclerotized insects, unless the chitinized cuticle is ruptured (Byersnd Thornhill, 1983). Scorpionflies were observed to suck the bodyuid of insects (Nakahara, 1922), and the extra-intestinal digestionas hypothesized to be aided with the acanthae of the proventri-

ulus (Hepburn, 1969a; Liu and Hua, 2009). The absence of a molarobe on the mandibles suggests that scorpionflies have no func-ion for grinding solid food. When feeding, they move and swinghe two mandibles laterally to pierce the cuticle of dead or dyingrthropods, and then insert the long rostrum into the body of prey.lack liquid with digestive enzymes from the midgut of scorpion-ies is injected into the food to extra-intestinally digest it into liquidefore being further ingested (Hepburn, 1969a). As a rule, insectshat ingest liquid diet require a tightly sealed proboscis, along withne or several fluid pumps (Borrell and Krenn, 2006; Kingsolver and

aniel, 1995). Based on our dissections, the labrum-epipharynx,alea and the posterior labium are the main components of theouthparts enclosing the preoral cavity in the Panorpidae. The

ntrinsic labro-epipharyngeal compressors arise on the anteriorabral plate and insert on opposing epipharyngeal walls in Mecop-

tal view of the distal labium; (C) posterior view of labial palpomere I; (D) mesal sidem’s bristles; BS4–6, basiconic sensilla IV–VI; m, mentum; pl1–2, labial palpomeres= 200 �m; B = 100 �m and C–F = 50 �m.

tera (Hepburn, 1969b). Therefore, we suggest that it is possible toform an airtight pump, which might be the possible mechanismof uptaking liquids. A pressure gradient develops along the preo-ral cavity because of the contraction of compressors in the airtightpump chamber such that the fluid is forced to enter the esopha-gus through the mouth. Since food products after extra-intestinaldigestion are in a state of slurry, which might contain more or lesssolid contents, the liquid-feeding scorpionflies must have a mecha-nism of filtration in order to prevent the large solid particles fromentering the mouth. In this circumstance, the dense microtrichiaand bristles on the galeae, laciniae, labial palpi, hypopharynx, andepipharynx may play an important part in the filtration of solid par-ticles of food. The distally furcated microtrichia on the mouthpartscould be interdigitated or even interlocked during feeding in orderto ensure the filtration effect of solid particles (Coronado-Gonzalezet al., 2008). The long microtrichia might be hydrophilic (Chapman,2003), serving to direct the flow of fluid from the food towardthe mouth, and likely playing a role of capillarity (Kingsolver andDaniel, 1995; Krenn et al., 2005) in the final process of uptakingliquids. The dense claw-like spines and the hair combs on the laci-niae might be associated with filtration (Palmer, 1998).

Acknowledgements

We thank Yao Wei and Hongmin Chen for assistance in specimencollection. Our thanks are also due to Guoyun Zhang for technicalassistance in scanning electron microscopy observation. Dr. James

Journal Identification = JMIC Article Identification = 1611 Date: March 5, 2011 Time: 2:40 am

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. Dunford and other two anonymous reviewers are greatly appre-iated for their valuable comments and suggestions for the revisionf the manuscript. This research was financially supported by theational Natural Science Foundation of China (grant no. 30670255).

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