Comparative study of larvae of Tenebrionoidea ( Coleoptera : Cucujiformia )

With approximately 30,000 described species and 30 currently recognised families (Lawrence & Newton, 1995), Tenebrionoidea is a large and complex superfamily of cucujiform beetles. The composition of the group is largely agreed upon (Lawrence & Newton, 1995). However, the monophyly is not well founded and the interrelationships of the families are largely unresolved despite of a considerable number of phylogenetic investigations (e.g. Crowson, 1966; Abdullah, 1973, 1974; Lawrence, 1977; Doyen & Lawrence, 1979; Pollock, 1995; Pollock & Lawrence, 1995). A large number of studies on tenebrionoid larvae have been published. However, most of them are not very detailed, and a thorough description of internal structures is only available for a single species, Tenebrio molitor (Jösting, 1942). Therefore, the main goal of this study is to improve the knowledge of the larval morphology of Tenebrionoidea. For the detailed descriptions, four larvae representing different families and morphological types were chosen: Orchesia micans (Panzer, 1794) (Melandryidae), Pseudolycus haemorrhoidalis (Fabricius, 1801) (Oedemeridae), Meryx sp. (Ulodidae) and Pytho niger Kirby, 1837 (Pythidae). The findings are compared to structural features of other tenebrionoid larvae, and a list of characters potentially useful for phylogenetic reconstruction and a character state matrix are presented (Table 1). The data for most families were taken from the literature (e.g., Lawrence, 1977, 1991; Lawrence & Spilman, 1991; Pollock, 1995; Pollock & Lawrence, 1995; Pollock et al., 2000; Selander, 1991; Young, 1991). A cladistic analysis was carried out even though it was apparent that the use of the larval characters alone would not be sufficient for a good resolution within the complex superfamily. It is likely that the inclusion of adult characters would have improved the results of the phylogenetic analyses. However, this would have been clearly beyond the scope of this study.


INTRODUCTION
With approximately 30,000 described species and 30 currently recognised families (Lawrence & Newton, 1995), Tenebrionoidea is a large and complex superfamily of cucujiform beetles.The composition of the group is largely agreed upon (Lawrence & Newton, 1995).However, the monophyly is not well founded and the interrelationships of the families are largely unresolved despite of a considerable number of phylogenetic investigations (e.g.Crowson, 1966;Abdullah, 1973Abdullah, , 1974;;Lawrence, 1977;Doyen & Lawrence, 1979;Pollock, 1995;Pollock & Lawrence, 1995).A large number of studies on tenebrionoid larvae have been published.However, most of them are not very detailed, and a thorough description of internal structures is only available for a single species, Tenebrio molitor (Jösting, 1942).Therefore, the main goal of this study is to improve the knowledge of the larval morphology of Tenebrionoidea.For the detailed descriptions, four larvae representing different families and morphological types were chosen: Orchesia micans (Panzer, 1794) (Melandryidae), Pseudolycus haemorrhoidalis (Fabricius, 1801) (Oedemeridae), Meryx sp.(Ulodidae) and Pytho niger Kirby, 1837 (Pythidae).The findings are compared to structural features of other tenebrionoid larvae, and a list of characters potentially useful for phylogenetic reconstruction and a character state matrix are presented (Table 1).The data for most families were taken from the literature (e.g., Lawrence, 1977Lawrence, , 1991;;Lawrence & Spilman, 1991;Pollock, 1995;Pollock & Lawrence, 1995;Pollock et al., 2000;Selander, 1991;Young, 1991).A cladistic analysis was carried out even though it was apparent that the use of the larval characters alone would not be sufficient for a good resolution within the complex superfamily.It is likely that the inclusion of adult characters would have improved the results of the phylogenetic analyses.However, this would have been clearly beyond the scope of this study.
The classification used here is based on Lawrence & Newton (1995) and von Kéler's muscular nomenclature is used in the text and the corresponding numbers in the illustrations (v.Kéler, 1963).
The data were coded as binary characters and entered into Winclada (Nixon, 1999).All characters were equally weighted.Tree searches were done in NONA (Goloboff, 1999).The trees were rooted automatically while executing the search (Nixon & Carpenter, 1993).The data matrix is provided in Table 1.
Salpingidae and Pyrochroidae as defined by Lawrence & Newton (1995) were treated as terminal taxa in the first analysis.Inopeplinae, Othniinae, Salpingidae sensu Lawrence (1991), Pedilinae and Pyrochroidae sensu Lawrence (1991) were treated as terminals in the second analysis (entries in italics in the data matrix; Table 1).

Orchesia micans (Melandryidae)
1.1.General appearance (Fig. 1a).Length of last instar larvae 5.3-6.7 mm (n = 6).Head shiny and of very light brown colour, with strongly sclerotised parts darkened; other parts of body largely unpigmented or yellowish in mature larvae.Legs well developed.Body slightly curved in lateral view and sub-cylindrical, posterior abdomen almost cylindrical.Abdomen about 2.4 times longer than thorax, segments V and VI slightly broader than other segments.Urogomphi absent.
1.12.Cerebrum suboesophageal complex (Fig. 5a).Fairly small in relation to size of head capsule.Posterior part of cerebrum not extending posteriorly into the prothorax.
1.13.Glands (Fig. 5a).A pair of coiled, tube-like glands with asymmetric position originates in the prothorax.They appear to open ventrolaterally close to the premental base.However, the exact distal orifice could not be identified.
1.14.Fat body.Only few and small sheets of fat body tissue present within head capsule (Fig. 8).

Abdominal segments IX and X (Fig. 11a).
Tergum roughly semicircular and in almost vertical position due to posterior extension of terga VII and VIII.Sternum short.Urogomphi absent.Small, transverse segment X enclosed between tergum and sternum of segment IX, ventrally oriented.

Internal skeletal structures (Figs 5b, 6b
). Anteriorly converging gular ridges continuous with developed postoccipital ridges posteriorly.Anterior part high, connected by well developed tentorial bridge (Fig. 6b), anteriorly continuous with strong posterior tentorial arms (Fig. 6b).Posterior arms strongly converging anteriorly.Dorsal arms not identified, extremely reduced or absent.Anterior arms present, attached to head capsule mesad to origin of antennal muscles (Fig. 5b).4b).Fairly short, 3-segmented, ventrally directed.Distal membranous part of articulating area appears antennomere-like in dorsal view.Proximal antennomere about 2.5 times longer than wide, antennomere II 3.5 times longer than wide, with ventrally inserted well developed sensorial appendage.Apical antennomere distinctly smaller than preceeding segments, about twice as long as sensorial appendage.
2.12.Cerebrum and suboesophageal complex (Fig. 5b).Comparatively small in relation to size of head capsule.Posterior part of cerebrum extends into anterior prothoracic region.Submentum almost completely located in prothorax.2.13.Glands (Fig. 5b).A pair of tube-like glands originates in the prothorax and opens between the bases of mentum and maxillae.

Prothorax (Figs 1b, 2b, 10b
). Slightly longer than following thoracic segments.All parts cream-white or testaceous, lightly sclerotised except for anterodorsal semimembranous collar and lateral marginal area of pronotum.Pronotum extending to lateral side of prothorax.Unsclerotised lateral part anteriorly adjacent with anterior transverse sternal plate and posteriorly with epimeral part of pleura.Anterior pronotum moderately arched, posterior part transformed into a distinctly bulging, transverse ampulla with asperities.Ventral side with extensive, transverse, bulging anterior plate, probably representing a fused presternum + cervicosternum, medially not distinctly separated from basisternal plate, which is inserted between the coxae.Indistinct, rounded line separates basisternum from the short, transverse sternellum, which is anteromedially inserted between the posterior part of the coxae.2b).Mesonotum with paired anterior ampullae with asperities.Posterior part moderately arched.Basisternum large, laterally adjacent with mesepimeron, bulging, with indistinctly delimited triangular anteromedian area.Laterotergite with membranous, setiferous protuberance (Fig. 2b).Pleural suture, episternum and epimeron exposed.Coxae widely separated.Legs similar to prothorax.Spiracle indistinct, located on small elevation above posterodorsal margin of prothoracic epimeral area.Coxae widely separated.Legs similar to prolegs.
2.18.Abdominal segments I-VII (Fig. 1b).Abdomen very slightly narrowing posteriorly.Distribution of setae as shown in Figs 1b and 11b.Segments II-V longer and broader than I and terminal segments, segment III longer than II, IV and V. Tergites II and III with paired ampullae with asperities slightly smaller than those of meso-and metathorax.
Unsclerotised pleural areas with membranous, setiferous protuberances, smaller and more clearly defined on anterior segments, broader on posterior segments.Sternites lightly sclerotised, separated from  11b).Segment IX round in cross section and with rounded posterior margin, without urogomphi.Sternite IX much shorter than preceeding sternites.Segment X posteroventrally directed, with separate dorsal tergal part and membranous ventral part.

Head capsule, external features (Figs
3.9.Epipharynx (Figs 5c, 6c).Anterior epipharynx slightly convex, with shallow median edge and very strong paramedian sclerotised longitudinal rods.Anteriormost part, i.e. ventral side of labrum, with longitudinal fields of internally directed microtrichiae.Fine microtrichiae also present between paramedian rods.Posterior part forming a very short preoral chamber together with the mandibular bases and the hypopharynx, and a moderately long prepharyngeal tube with the posterior hypopharynx.Prepharynx with distinct dorsolateral and ventrolateral folds, and an almost quadrangular shape in cross section.
Transverse muscles are present between the anterior components of M 43 and between M 43 and M 45. tum.Surface with strong, dorsally directed setae and short spines.Lateral walls of labio-hypopharyngeal complex connected by strong internal bar, which is posteriorly interrupted and connected by fibrillar structures.Posterior margin of anterior hypopharynx demarcated by transverse bar.Posterior hypopharynx fused with epipharynx laterally, forming a wide prepharyngeal tube, which is almost quadrangular in cross section.
Musculature (Fig. 5c): M 41: M. frontohypopharyngalis, O: central area of frons, between M 9 and M 11, I: on a strong lateral hypopharyngeal apodeme at the hind margin of the prepharyngeal tube; M 42m: M. tentoriohypopharyngalis medialis, a pair of thin bundles, O: not clearly identified, probably from apical part of posterior tentorial arms, I: medially on the ventral wall of the prepharyngeal tube; M 42l: M. tentoriohypopharyngalis lateralis, thin muscle fibres, O: proximal part of dorsal tentorial arm, I: laterally on hind margin of prepharyngeal tube.
Well developed ring muscles present over the whole length of the pharynx (Fig. 5c) 3.12.Cerebrum and suboesophageal complex (Fig. 5c).Cerebrum located in the posterior head region, asymmetric.Suboesophageal complex laterally enclosed by gular ridges.
3.13.Glands (Fig. 5c).A pair of tube-like glands originating in the prothorax.The precise location of the opening in the preoral area could not be identified with the available microtome sections.
3.14.Oesophagus.Posterior oesophagus modified as proventriculus, with moderately thick cuticle, ventral, lateral and dorsal folds and a well developed layer of thin ring muscles.
3.15.Fat body.Present in the posteriormost part of the head.1c, 2c, 10c).Slightly longer than following thoracic segments and equally broad (Fig. 1c).Tergite distinctly sclerotised and dark brown in colour, medially divided by a very thin suture, laterally extending to pleural area, almost saddle-like.Dorsal side and anterior and posterior margins with very long setae (Figs 1c,2c).Areas anteriorly and posteriorly adjacent with tergum sclerotised but unpigmented, with longitudinal parallel striae.Laterotergite broad, largely semimembranous, but with indistinct posterior sclerotised area with a long seta.Anteromedian part of sternum probably composed of the presternum and cervicosternum, reaching gula anteriorly, slightly sclerotised and bulging, with pair of ventrally directed setae (Fig. 10c).Other parts undivided, unsclerotised and unpigmented, not clearly separated from pleural parts.Pleural suture above coxal cavity distinct, not completely dividing lightly sclerotised episternum and epimeron.Legs distinctly separated, 5-segmented, composed of conical coxa with several strong spines anterodistally, well developed trochanter, femur, tibiotarsus, and a strong pretarsal claw with two setae (Figs 2c, 10c).1c, 2c).Shorter than prothorax.Tergum sclerotised and dark brown, with sharp anterior edge but without asperities, sligthly narrower than protergum.Median suture, adjacent sclerotised, unpigmented areas and setation similar to prothorax.Upper parts of pleura semimembranous.Episternum and epimeron separated by short pleural suture, very lightly sclerotised and pigmented.Anteromedian part of sternal area distinctly bulging, main part without clearly separated areas, largely unsclerotised.Annularbiforous stigma located on small anterolateral pleural elevation close to intersegmental border.Legs similar to prothoracic legs, slightly longer.
3.20.Abdominal segment VIII (Fig. 11c).Tergum slightly longer and darker, with very strongly pronounced anterior edge, otherwise similar to segments I-VII.
3.21.Abdominal segments IX and X (Fig. 11c).Tergum IX with strongly sclerotised, very dark dorsal part, with numerous large tubercles and long setae (Fig. 11c).Lateral parts and almost vertical posterior part lightly sclerotised and testaceous.Sternum IX simple, shorter than preceeding sterna.Well developed urogomphi arise from dorsal part of tergum, distinctly curved upwards.Apical part largely smooth, without accessory process.Segment X posteriorly directed, with well developed, lightly sclerotised tergal part with long, posteriorly directed setae, and a largely membranous sternal part with few setae and posteriorly directed, papilla-like structures.
Abdomen more than three times longer than thorax.Tergite IX plate like, extending to ventral side, with distinct urogomphi.2d, 3d, 4d,  5d).Head slightly retracted, prognathous, with dorsal side almost horizontal, laterally rounded, greatest width at posterior third of head capsule.Setation as shown in Figs 2d, 3d and 4d.Antennae inserted on moderately protruding, sclerotised elevation anterior to stemmata.Five stemmata present, arranged in a vertical anterior row of three and a vertical posterior row of two.Labrum moveable, connected to clypeus by a membranous fold (Fig. 5d).Clypeus fairly long, with broad transparent anterior margin, fused with frons posteriorly.Frontal suture (= frontal arms) lyriform, transverse anteriorly, with distinct anterolateral section reaching posterior margin of antennal articulation area.Frons broad anteriorly, almost reaching posterior margin of head capsule posteriorly, posterior margin slightly concave.Coronal suture present but very short, covered by anterior margin of prothorax.Dorsal endocarina absent.Hypostomal rods absent.Epicranial ridges distinct.Maxillary grooves deep.Gula broad, moderately long, slightly convergent anteriorly, fused with submentum, laterally delimited by very distinct gular suture.Posterior tentorial grooves posterior to maxillary groove fissure-shaped, continuous with gular ridge.Posterior part of gula covered by anteromedian prosternal plate.Posteriormost part of ventral side of head closed by broad semimembranous area with low lateral ridges and a median postgular sclerotisation.Dorsal membranous fold connecting head and thorax with paired transverse cervical sclerites.3d, 4d, 6d).Fairly long, about 1/3 of maximum head width, 3-segmented.Antennomere I and II elongate, about three times longer than wide.Sensorial appendage of antennomere II small and conical, inserted ventrally on apical membranous area.Antennomere III slightly shorter than I and II and slender, with apical group of fairly long sensillae.

Head capsule, external features (Figs
Musculature (Fig. 6d): Mm 1, 2, 4: M. tentorioscapalis anterior, posterior, medialis, O: dorsal wall of head capsule, lateral to attachment of dorsal tentorial arms, I: anteroventrally, posteriorly, and dorsally on the base of antennomere I.  4d, 5d).Submentum trapezoidal, anteriorly narrowing, posteriorly fused with gula, border between both areas demarcated by a distinct edge.Mentum widened anteriorly, with a pair of ventrally directed setae.Proximolateral margin covered by pad-like maxillary articulatory area.Prementum broad and short, with short, 2-segmented palps.Both palpomeres about equally long.Ligula sclerotised and well developed, extending anteriorly beyond apex of palps, with pair of anteriorly directed setae and a very dense apical field of microtrichiae.
A very strongly developed transverse muscle connects the lateral walls of the mentum.5d, 6d, 7d).Anterior part moderately convex, with indistinct median ridge.Median part densely covered with very short, mesally directed microtrichiae.Intermediate epipharyngeal section flat, forming preoral chamber together with mandibular bases and hypopharynx.Posterior part laterally fused with hypopharynx, forming broad and flat, moderately long prepharyngeal tube.
Transverse muscles are present between the bundles of M 43 and M 45. 5d, 7d).Anterior part posteriorly adjacent to dorsal side of ligula, with distinct lateral edges with very dense longitudinal combs of hairs and a convexity between them.Dense transverse brush of stronger hairs present on transverse bar anterior to opening of preoral chamber (= transverse sclerome), left side of sclerome with molar-like modification.Posterior part of hypopharynx forming floor of preoral chamber or prepharyngeal tube, respectively, devoid of hairs or microtrichiae.
4.12.Cerebrum and suboesophageal complex (Fig. 5d).Cerebrum and suboesophageal complex located in posterior head region, relatively small in relation to head size.Suboesophageal complex reaching tentorial bridge anteriorly.
4.13.Glands.A pair of tube-like glands originating in the prothorax.The precise location of the distal opening could not be identified.
4.14.Fat body.Voluminous tube-like compartments of the fat body present in the posterior part of the head.1d, 2d, 10d).Longer than following thoracic segments and equally broad (Fig. 1d).Setation as shown in Figs 1d, 2d and 10d.Tergite flat, sclerotised and shiny, but almost completely unpigmented like other parts of body segments, separated into two halves by median suture, with distinct lateral edge and broad, sclerotised inflected part.Large, flat anteromedian plate of sternum probably composed of the presternum and cervicosternum, covering posterior part of gula anteriorly, incompletely divided by a pair of paramedian ridges, with two pairs of ventrally directed setae.Basi-sternum large, fused with episternal area anterior to coxae, with distinct sternal apophyseal pits posteriorly.Small, paired, triangular sclerites between apophyses and posteromesal coxal margin possibly represent a part of the sternellum, separated from epimeral area by a suture.Pleural suture above coxal cavity distinct, clearly dividing episternal and epimeral areas (Fig. 2d).Legs broadly separated, fairly long, 5-segmented, composed of conical coxa with anterior row of spines, well developed trochanter, femur, tibiotarsus, and a strong pretarsal claw (Figs 2d, 10d) with two setae.1d, 2d).Shorter than prothorax.Tergum with median suture and medially interrupted transverse ridge shortly posterior to anterior margin.Lateral edge less distinct, inflected part of tergum moderately broad.Exposed part of pleural suture short.Intersternite fairly broad, with separate lateral piece.Sternum undivided.Spiracle located on elevation between posterior inflected margin of protergum and anterior inflected margin of mesotergum, annular with crenulate margin on one side.Legs similar to prothoracic legs.
4.18.Abdominal segments I-VII (Fig. 1d).Abdomen subparallel, elongate and strongly flattened.Segments very slightly rounded laterally, with lateral groups of long setae.Other setae as shown in Fig. 1d.Segment I shorter than following segments.All segments with distinct anterior ridges (= parabasal ridges sensu Pollock, 1991) with median processes [see Fig. 1d (indicated by arrow) and Pollock, 1991].Segments II-VII with short, paramedian, longitudinal ridges.Tergites not separated from pleural area.Flat and sclerotised sterna separated from lateral part of segments by distinct longitudinal fold.Spiracles close to anterior margin of segments.1d, 11d).Slightly longer than segment VII, with almost straight lateral margin.Paramedian ridges very short.Sternite VIII and IX indistinctly separated medially.1d, 11d).Segment IX strongly sclerotised, with a semicircular row of eight large tubercles on dorsal side and strong, fixed urogomphi with three mesally directed projections.Pit between urogomphi broad, dark and strongly sclerotised.Tergite extending ventrally to form entire terminal segment (= urogomphal plate), with an arch of six quadrangular sclerites around sternite IX and segment X. Quadrangular sternite IX with an anterior row of 20-21 subequal asperities, indistinctly separated posteriorly from strongly reduced, ventrally directed sternum X.
32. M. tentoriopharyngalis posterior: (0) one group of muscles, origin from the tentorial bridge or ventral wall of head capsule; (1) 2-3 groups of muscles with origin from the gular ridges and the posterior tentorial arm.M. tentoriopharyngalis posterior is divided into several subunits, which arise from the gular ridges and the posterior tentorium in the larvae of Tenebrionoidea examined (less strongly developed in Orchesia and with origin shifted to postoccipital ridge).
53. Hypermetamorphosis: (0) absent; (1) present.Rhipiphoridae and Meloidae are characterised by hypermetamorphosis.However, the triungulin and post-triungulin larvae differ distinctly in both families.The hypermetamorphosis is correlated with parasitism in Rhipiphoridae, but with specialised predatory habits in larvae of Meloidae.Meloid larvae feed on eggs, immatures and provisions of other insects in the T-(triungulin) and FG phase (Selander, 1991).

DISCUSSION
Considering the complexity and morphological heterogeneity of Tenebrionoidea, it was not surprising for us that the larval data presented here were not sufficient for a satisfying clarification of the relationships of the families.Therefore, the results have to be treated as very preliminary, and the characters presented above may be mainly considered as a basis for more comprehensive future analyses.
Tenebrionoidea (incl.Ciidae and Prostomidae) was well supported as a clade by several larval autapomorphies (Figs 13,14).Potential synapomorphies of all tenebrionoid families are a posteriorly diverging gula with well developed gular ridges (16.1), anteriorly shifted posterior tentorial arms (17.1;in contrast to Cleroidea and Cucujoidea), asymmetric mandibles (19.1), the absence or vestigial condition of M. craniocardinalis (31.1), and the subdivision of M. tentoriopharyngalis posterior into several bundles arising from the gular ridges (32.1).Whether some or all of these characters are indeed tenebrionoid autapomorphies is uncertain at this stage.However, it is rather obvious that modifications of the posteroventral head capsule and tentorium of larvae played an important role in the early evolution of the superfamily.Two other features are charactersistic for tenebrionoid larvae, but were not confirmed as autapomorphies here: the absence of the prostheca (possible exception in Ciidae: 23.0;Lawrence, 1991), and a rounded or truncate maxillary mala (28.0/1).
Apart from the few features shared by all or most tenebrionoid larvae, the group is highly heterogenous in terms of larval morphology.The larval body is generally subparallel (Fig. 1) and a slightly flattened thorax and abdomen may be considered as a groundplan condition of the superfamily [e.g., Mycetophagidae, Archeocrypticidae, Melandryidae (Fig. 2a), Zopheridae (Fig. 2c); Lawrence, 1991].However, distinctly different body shapes have evolved in correlation with different habits.A nearly cylindrical body seems to be typical for larvae boring in wood or compact mushroom fruiting bodies (Ciidae, Mordellidae; Costa et al., 1988;Lawrence, 1991), c-shaped and grub-like bodies are correlated with specialised developmental strategies (post-triungulin larvae of Rhipiphoridae and Meloidae), and a strongly flattened condition (1.1) has apparently evolved as an adaptation to subcortical habits [e.g., Prostomidae, Pythidae (Fig. 2d), Pyrochroidae].However, life under bark is not necessarily correlated with a flattened body.Thorax and abdomen are subcylindrical in the larvae of Bitoma (Colydiidae), which also live in subcortical habitats.
The shape of the head capsule also varies greatly, usually in correlation with the body shape.A subprognathous or prognathous head with anteriorly sloping dorsal side may represent the ancestral state (e.g., Melandryidae, Colydiidae; Fig. 2a-c).A globular head capsule with ventrally oriented mouthparts (3.1) has evolved in Ciidae and Mordellidae (Fig. 12b).This condition is possibly correlated with an elongate coronal suture in both families (9.1) and with a reduced gula in Mordellidae.A distinctly prognathous head, with almost horizontal dorsal side and anteriorly directed mouthparts is found in all larvae with strongly flattened body (e.g., Prostomidae, Pythidae, Pyrochroidae, Boridae; Fig. 2d), but also in some other taxa (e.g., Synchroidae).
Endocarinae, which serve as additional muscle attachment areas and strengthen the head capsule, have apparently evolved several or many times independently.They occur as median-, paired or Y-shaped ridges (Fig. 3b; chars.[4][5][6], and may be present or absent or variously shaped in representatives of a single family (e.g., Ciidae, Tetratomidae, Melandryidae, Colydiidae).
The length of the coronal suture varies considerably and this is likely correlated with the head shape (Fig. 3; see above).A shortened or absent coronal suture (8.1) is usually found in larvae with a strongly prognathous head (e.g., Prostomidae, Pyrochroidae, Pythidae; Figs 1d, 3d), and an elongate coronal suture in larvae with a globular head capsule (e.g., Mordellidae).A distinctly asymmetric coronal suture as is found in larvae of Pterogeniidae (Lawrence, 1977) is likely an autapomorphy of this family.
The frontal arms are probably primarily lyriform with distinct lateral loops (11.0).This condition is found in most tenebrionoid families (Figs 3c, d) and in the outgroup taxa.V-shaped frontal arms occur in several groups [e.g., Ciidae, Melandryidae part.(Fig. 3a), Zopheridae part., Tenebrionidae part., Stenotrachelidae part., Oedemeridae part.(Fig 3b ); Costa et al., 1988;Lawrence, 1991].Forked frontal arms occur within Tetratomidae.The absence of the frontal arms is likely autapomorphic for Mordellidae, and this seems to be characteristic for boring larvae with a globular head (Lawrence, pers. comm.).An unusual feature is the presence of a transverse ecdysial line connecting the frontal arms.However, the results of the analysis show that this character state has evolved three times independently.It is apparent that the condition of the frontal arms is of limited value for the phylogenetic reconstruction of Tenebrionoidea.
Posteriorly divergent hypostomal ridges (Fig. 4a-c; char.14) are probably present in the groundplan of the superfamily and were lost several times independently [e.g., Tetratomidae part., Melandryinae part., Zopheridae part., Trictenotomidae, Pythidae (Fig. 4d)].Ventral epicranial ridges are missing in most tenebrionoid larvae.It is likely that they have evolved several times independently (e.g., Ciidae, Tenebrionidae part.).At least their presence in larvae of Trictenotomidae and Pythidae (hypostomal ridges absent) may be considered as a potential synapomorphy of these families (see below).
The mandibles of tenebrionoid larvae vary considerably.Asymmetry (19.1), the presence of two or three apical teeth, a tuberculate mola (20.0, 22.0), and the absence of a prostheca (23.1) may be groundplan features of the superfamily, but other interpretations are possible.It is rather obvious that the mola became reduced several times independently [e.g., Tetratomidae part., Melandryidae part.(Fig. 6a), Colydiidae part., Mycteridae part.].The presence of a tooth on the left mandible (Fig. 6d; 21.1) is a characteristic feature of tenebrionoid larvae.However, a reliable evolutionary interpretation of this character is very difficult at present.The tooth is likely used as a crushing device.A close functional relation between the mandibular molae and the hypopharyngeal sclerome was pointed out by Lawrence (1977).Whether the molar-like sclerome (30.1) has evolved several times independently or is a possible autapomorphy of a tenebrionoid subgroup remains an open question.
The maxillae are almost always inserted in a distinct maxillary groove (Fig. 5) with a well developed articulating membrane (24.0).The articulatory area is reduced in most ciid larvae (see below) and the specialised larvae of Rhipiphoridae and Meloidae.A pad-like modification of the membrane (Fig. 4d; 25.1) is a derived condition and a possible synapomorphy of Synchroidae, Prostom-idae and the pythid-salpingid and anthicid-scraptiid lineage (Fig. 13).
The presence of an undivided mala is a groundplan feature of Tenebrionoidea (and Cucujiformia).The condition in Ciidae, i.e. the presence of a separate internal and external lobe (26.0) is certainly the result of reversal and an autapomorphy of this family.The presence or absence of a tooth-like projection on the mala (uncus) is highly variable even at the family level [e.g., Tetratomidae, Colydiidae, Zopheridae (Fig. 7c), Tenebrionoidae, Stenotrachelidae] and is apparently of limited value for phylogenetic reconstruction on a higher level.The rounded apex of the mala is probably a groundpan feature of Tenebrionoidea, and distinguishes their larvae from those of most groups of Cucujoidea.The truncate condition (Figs 7b,d;28.1)has apparently evolved many times independently and varies even at the family level, like the presence or absence of an apical cleft (29.1; e.g., Melandryidae, Stenotrachelidae).
The musculature of the head of tenebrionoid larvae is characterised by the presence of a strong frontoepipharyngeal muscle (M 9; Fig. 5) (absent in Prostomis as a result of an extremely flattened head; Schunger et al., 2003), a moderately sized or weakly developed prepharyngeal dilator (M 43), dorsal and ventral postpharyngeal dilators composed of several bundles (M 46), or subcomponents (M 52; Figs 5,7), respectively.The maxillary musculature is similar to that found in cucujoid larvae and many others.However, the cranial muscle of the cardo is very thin or even absent in most tenebrionoid larvae (Fig. 7).A tendency to reduce the premental retractors is shared with larvae of Cucujoidea and Cleroidea (Beutel & Pollock, 2000;Beutel & lipi ski, 2001).At least one of the three muscles (Mm 28-30) is absent.
The cerebrum and suboesophageal complex are generally located in the posterior region of the head capsule in tenebrionoid larvae (Fig. 5).The relative size is negatively correlated with the size of the head.A complete shift of the brain to the thorax as it is found in all cleroid larvae examined (Beutel & Pollock, 2001) was not observed in larvae of Tenebrionoidea.
Characters of the thorax were not very informative for phylogenetic reconstruction.The presence of an elevated mesothoracic spiracle (34.1) was interpreted as a plesiomorphic feature in our analysis (see above).This is obviously due to its shared presence in the two outgroup taxa (Derodontidae, Protocucujidae) and almost certainly incorrect, since this condition is absent in the vast majority of beetle larvae.A characteristic, almost certainly derived feature is the subdivision of the anterior prosternal plate (33.1).However, the results of our analysis suggest that this condition has evolved several times independently within the pythid-salpingid group.It is possible, however, that this character state is at least synapomorphic for Boridae and Pyrochroidae (Fig. 14).
Modifications of abdominal structures provide phylogenetically useful characters, especially for the pythidsalpingid lineage.A strong elongation of segment VIII (36.1) is a condition characteristic for Mycteridae, Boridae and Pyrochroidae (see below).A feature shared by Prostomidae, the pythid-salpingid lineage, and the anthicid-scraptiid lineage is the nearly horizontal, platelike tergum IX (37.1).A very unusual apomorphic character state is the articulation between segments VIII and IX (38.1).It is a shared derived condition of Prostomidae, Mycteridae, Boridae, Pyrochroidae and Inopeplinae.A feature not known from other beetles is the subdivision of the ventral part of tergite IX into several plates (39.1).This condition is found in Trictenotomidae and Pythidae (Figs 13,14).A derived feature shared by Mycteridae, Boridae, Pyrochroidae and Inopeplinae is a sternite IX partly enclosed by sternite VIII (44.1).
The strict consensus trees (Figs 13,14) show a low resolution.One result, which may be considered as a working hypothesis, is the sistergroup relationship between Synchroidae and a clade comprising Prostomidae, the pythid-salpingid lineage and the anthicidscraptiid lineage (Fig. 13).Potential synapomorphies are the distinctly prognathous head (2.1) and the pad-like maxillary articulating area (25.1).The plate-like tergum IX (37.1) is a possible synapomorphy of this group excluding Synchroidae.The monophyly of groups comprising Trictenotomidae + Pythidae seems to be well supported (see above).A clade comprising Prostomidae + (Mycteridae + Boridae) [strongly flattened body (1.1), articulation between segment VIII and tergum IX (38.1)] is supported when Salpingidae and Pyrochroidae as defined by Lawrence & Newton (1995) are treated as terminal taxa.An elongated segment VIII (36.1) and a sternite IX enclosed by sternum VIII are potential synapomorphies of Mycteridae and Boridae.This implies parallel evolution in Pyrochroidae for both characters.
When Othniinae, Inopeplinae and Pedilinae are treated as separate terminals, the number of minimum length trees is distinctly reduced.The monophyly of Salpingidae sensu Lawrence & Newton (1995) was not confirmed.Othniinae form a clade with Trictenotomatidae and Pythidae (Fig. 14).Pyrochroidae sensu Lawrence & Newton (1995) were also rendered paraphyletic with Pyrochroidae sensu Lawrence (1991) isolated from Pedilinae and as sister taxon of Boridae (characters see Fig. 14).This would reduce homoplasy as it would not imply that the strongly flattened body (1.1), the elongation of segment VIII (36.1), the articulation between segment VIII and tergum IX (38.1), and the enclosure of sternite IX by sternum VIII (44.1) have evolved independently in Pyrochroidae (sensu Lawrence, 1991).
Salpingidae and Pyrochroidae as defined by Lawrence & Newton (1995) are quite heterogenous in their larval morphology and the monophyly of the groups should be critically evaluated in a cladistic study with a more comprehensive data set (e.g., adult morphology).
Another clade in our strict consensus trees is formed by Meloidae and Rhipiphoridae.This is likely an artefact as the derived features shared by both groups are probably related with the specialised life style (e.g., absence of the maxillary articulating area and mandibular mola).Mordellidae are probably not closely related to Ciidae (see Lawrence, 1991), even though they share several features with this family (shape of head and body, elongate coronal suture, distinct frontoclypeal suture, shortened antennae, reduced mola).It is likely, that these derived features have evolved with a similar life style.Larvae of Mordellidae are distinguished from most other tenebrionoid larvae by the globular head, the elongate coronal suture, the orthognathous position of the mouthparts, reduced stemmata and the subcylindrical body (see above).The absence of frontal sutures and the reduced condition of the legs are autapomorphies of the family.
The characters examined show that some taxa are isolated in terms of larval morphology within the families they are assigned to.Larval features suggest a basal position of Sphindocinae within Ciidae.Unlike other representatives of the family they possess 3-segmented antennae and a well developed maxillary articulatory membrane.Loss of antennomere III and a maxillolabial complex very similar to that of elateriform (Beutel, 1995) or cleroid larvae (Beutel & Pollock, 2000) are potential autapomorphies of Ciinae.Orchesia may belong to a monophylum within Melandryidae, which is characterised by strongly shortened antennae and the absence of urogomphi (Figs 1d,4a).The strongly reduced tentorium (Fig. 7a), the weakly developed M. tentoriopharyngalis posterior, and the presence of a strong transverse muscle connecting the posterior tentorial arms (Fig. 8a) are other unusual features of Orchesia, but the condition in other members of the family is unknown.Larvae of Calopus (Calopinae) are distinguished from other oedemerid larvae by several plesiomorphic features, e.g., lyriform frontal sutures, presence of 2-3 apical mandibular teeth, presence of hypostomal ridges, and well developed upturned urogomphi.Larvae of Penthe (Penthinae) differ from other tetratomid larvae by the presence of a median endocarina, a mola transformed into a membranous lobe, a long and narrow ligula, absence of the hypostomal ridges, patches of asperities on meso-and metatergites and on the abdominal tergites I-VIII, and a simple apex of the urogomphi (Lawrence, 1991).
It is obvious that the larval characters are insufficient for the clarification of tenebrionoid relationships (see above).Obvious problems are the complexity of the group, the uncertain monophyly of families (Lawrence & Newton, 1995), and lack of information, especially on internal structures.Another major problem is the high degree of homoplasy.This is reflected by the low consistency indices (see above).Structures which are highly variable even within families are the endocarina, the coronal, frontoclypeal and frontal sutures, the hypopharyngeal ridge, the mandible, the mala, the urogomphi, the asperities of sternum IX, and the spiracles.Taxa which are highly polymorphic in their larval morphology are Tetratomidae (8 polymorphic characters), Melandryidae (15 polymorphic characters), Colydiidae (13 polymorphic characters), Zopheridae (10 polymorphic characters), and Stenotrachelidae (8 polymorphic characters).The monophyly of some of these families appears questionable considering the larval features (see also Lawrence & Newton, 1995).
The strategy for establishing a well founded phylogeny of Tenebrionoidea should be to take a stepwise approach.Single families or potentially monophyletic subunits comprising several families should be analysed with genera or tribes as terminals, and the groundplan of these groups should be established for different stages.The analysis based on groundplans of larger subunits and a broad spectrum of characters may eventually lead to a convincing phylogenetic hypothesis for this large and complex lineage of Coleoptera.
able specimens.The thorough review of the manuscript by S.A. lipi ski and D.A. Pollock is also gratefully acknowledged.
Pleural suture and episternal part of pleura not exposed, covered by unsclerotised lateral part of pronotum and lateral part of anterior sternal plate.Epimeral part connected with sternellum posteriorly.Coxae widely separated, broad and oblique.Trochanter well developed, appearing fused with femur mesally.Femur longer than other leg segments, slightly extended distally.Tibia conical.Tarsungulus well developed, with two setae (Figs 2b, 10b).Setation of other parts as shown in Figs 1b, 2b and 10b.2.16.Mesothorax (Figs 1b,

4. 6 . 4 . 7 .
Mandible (Figs 5d, 6d).Distinctly asymmetric.Broad at base, with slender distal part with two apices and 2 small subapical teeth.Molae present, asymmetric, with transverse ridges.Left mandible with prominent molar tooth.Musculature (Figs 5d): M 11: M. craniomandibularis internus, largest muscle of the head, O: extensive parts of the dorsal, dorsolateral and ventrolateral areas of the head capsule, I: adductor tendon; M 12: M. craniomandibularis externus, O: lateral wall of head capsule, I: abductor tendon.Maxilla (Figs 4d, 7d).Articulatory area pad-like.Cardo transverse, connected with stipes by a hinge, divided by an internal ridge.Mala broad, apicolaterally rounded, very shallowly cleft anteromesally, with a mesally directed protuberance with three distinct teeth.Anterolateral margin with a group of longer anteriorly directed setae, anteromesal margin and mesal margin proximal to protuberance with stronger and shorter mesally directed setae.Palp 3-segmented and fairly short.Distinct palpifer not developed.Palpomeres stout, about twice as long as broad.Apical palpomere with a dense apical field of minute sensillae.Musculature (Figs 5d, 7d): M 15: M. craniocardinalis, an extremely thin bundle between the two subcomponents of M 19, O: posterior to M 19, ventrolaterally on posterior margin of head capsule, I: laterally attached to cardinal base by means of a thin tendon; Mm 17/18: Mm. tentoriocardinalis and -stipitalis, several strong bundles, O: posterior tentorial arm, I: ventral surface of cardo and stipes and mesal stipital edge; M 19: M. craniolacinialis, two parallel bundles, O: ventrolaterally from posterior part of head capsule, between bundles of M 11, I: base of mala; Mm 22/23: M. stipitopalpalis externus and internus, represented by two parallel bundles, O: ventral surface of stipes, I: laterally on base of maxillary palp.4.8.Labium (Figs

Fig. 13 .
Fig. 13.Strict consensus tree (L = 120) of 2650 most parsimonious cladograms with a length of 85 steps.Characters marked by full squares are non-homoplastic (character states below squares).

TABLE 1 .
Character state matrix.