Phylogenetic analysis of Myxophaga (Coleoptera) using larval characters

A phylogenetic parsimony analysis of fifty-four larval characters of Myxophaga (excluding Lepiceridae) resulted in two minimal length cladograms. The monophyly of Torridincolidae, Hydroscaphidae and Microsporidae is supported by several autapomorphies: miniaturization, flattened body with laterally extended tergites, broadened head, scale-like surface structures, broad tentorial bridge, disc-shaped labral sensilla, spiracular gills and pupation in the last larval exuviae. Hydroscaphidae are the sister group of Microsporidae. Larvae of both families are characterized by semi-entognathous mouthparts, tergites with posterior rows of lancet-shaped setae, claws with flattened basal spines and balloon-shaped spiracular gills. The monophyly of all families is supported by autapomorphies. Torridincolidae excluding Delevea is defined as a monophylum by four derived character states: body ovoid, thorax semicircular and as long as abdomen, labral sensilla fused and abdominal sternite IX distinctly reduced and triangular. The monophyly of Torridincolinae (sensu Endrödy-Younga 1997b) is supported by two autapomorphies. The proposed branching pattern suggests that the early representatives of Myxophaga (excluding Lepiceridae) were living in aquatic conditions with a preference for hygropetric habitats. The tendency to live on rocks in running water and miniaturization have played an important role in myxophagan evolution.     

Cephalic anatomy of Sphaeriusidae and a morphology‐based phylogeny of the suborder Myxophaga (Coleoptera)

Myxophaga are a small group of beetles, but phylogenetically crucial as one of the four coleopteran suborders. The monogeneric Sphaeriusidae, one of four myxophagan families, comprise about 20 species, most of them living in moist substrate at river edges. The morphology of the minute hemispherical adult is very insufficiently known. Consequently, we document external and internal head structures using scanning electron microscopy, microtome sections and three‐dimensional reconstructions. The results are discussed with respect to effects of miniaturization and also functional aspects, especially microphagous feeding habits. The head of Sphaerius is less affected by size reduction compared with other beetles of the same size class (e.g. larger Ptiliidae, Corylophidae). Features related to very small size are the absence of externally visible ridges and a partial shift of the brain into the prothorax. The cephalic musculature is apparently not affected. The feeding apparatus is similar to what is found in microphagous species of Polyphaga, especially in Scirtoidea and Staphyliniformia. However, in contrast to polyphagans with similar feeding habits, the hypopharyngeal longitudinal ridge (or process) of Sphaerius is strongly reduced and a fimbriate galea is lacking. The observed features are also evaluated in a cladistic analysis of larval and adult characters. The results are distinctly in conflict with branching patterns suggested by analyses of molecular data, but in agreement with previous morphological studies. In contrast to a pattern obtained in a recent molecular study – (Hydroscaphidae + (Torridincolidae + (Sphaeriusidae + Lepiceridae))) – our analyses yielded Lepiceridae as sister to the remaining Myxophaga (branch support 9), and Sphaerius as sister taxon of Hydroscaphidae (branch support 5). The monophyletic origin of the latter two taxa is supported by unusual synapomorphies of adults and larvae. Sphaerius is characterized by numerous autapomorphies of the head: a labro‐mandibular locking device, a bipartite M. frontoepipharyngalis (M9) with subcomponents oriented in the opposite direction, a deep antennal furrow, an intercalary antennomere with a structure resembling a sucking disc, a strongly elongated flagellomere 1, a compact three‐segmented antennal club, strong bundles of M. tentorioscapalis (M4) originating on the posterior head capsule, a concave anterior side of maxillary palpomere 2, and an elongated second pair of tormae posteriorly connected with a process of the hypopharyngeal suspensorium.     

The head morphology of Clambidae and its implications for the phylogeny of Scirtoidea (Coleoptera: Polyphaga)

External and internal structures of the head of adults of Clambus are described and illustrated in detail. The results are compared with structural features found in the clambid genus Calyptomerus, in representatives of other scirtoid families, and also in species of other coleopteran suborders, notably Myxophaga. The results tentatively support the monophyly of Scirtoidea and a close relationship between Clambidae and Eucinetidae is suggested by one shared derived feature of the mandible, a long and slender apical tooth with a serrate edge. The monophyly of Clambidae is very strongly supported and Acalyptomerus is probably the sistergroup of a clade Calyptomerus + Clambinae. Potential scirtoid autapomorphies are the loss of the dorsal tentorial arms, a bulging gula, a strongly transverse labrum, and a ridge separating the mediostipes from the lacinia. However, all these features are homoplasious. The monophyly of Clambidae is supported by modifications of the head capsule which is strongly flattened and broadened, by a deep clypeofrontal incision enabling vertical antennal movements, and a series of antennal features. Synapomorphies of Clambinae + Calyptomerus (Clambidae excluding Acalyptomerus) are the conglobate body form with the ventral side of the head capsule in contact with the mesocoxae, and compound eyes integrated in the contour of the head. The completely subdivided eye is an autapomorphy of Clambus. An entire series of features is shared by Clambidae (or Scirtoidea) and Myxophaga. Most of them are apomorphies that apparently evolved independently in both groups. However, the presence of well‐developed maxillary and labial glands is arguably a retained groundplan feature of Coleoptera, with parallel loss in Archostemata, Adephaga and various groups of Polyphaga. J. Morphol. 277:615–633, 2016. © 2016 Wiley Periodicals, Inc.     

Basal relationships of Coleoptera inferred from 18S rDNA sequences

The basal relationships of the hyperdiverse insect order Coleoptera (beetles) have proven difficult to resolve. Examination of beetle suborder relationships using 18S ribosomal DNA reveals a previously unproposed relationship among the four major lineages: [(Archostemata(Myxophaga(Adephaga, Polyphaga)))]. Adding representatives of most other insect orders results in a non-monophyletic Coleoptera. However, constraining Coleoptera and its suborders to be monophyletic, in analyses of beetle and outgroup sequences, also results in the above beetle relationships, with the root placed between Archostemata and the remaining suborders.     

Discovery of swimming larvae in Elmidae (Coleoptera: Byrrhoidea)

The aquatic larvae of the family Elmidae (Coleoptera) have been considered unable to swim because they lack swimming setae on their body and legs. We discovered that riffle beetle larvae (Leptelmis gracilis Sharp) are in fact able to swim. After opening the tuft‐like gills on the last abdominal segment they swim by repeatedly bending the abdomen into a U‐shape very quickly and in a wavy manner, while their head and thorax move anteriorly, resulting in a sigmoidal body shape. The flat bodies of L. gracilis larvae could be advantageous for swimming compared to the cylindrical or semicylindrical bodies of larvae in related genera.     

The larval head of Raphidia (Raphidioptera, Insecta) and its phylogenetic significance

External and internal head structures of larval representatives of Raphidiidae are described. The obtained data were compared to characters of other neuropterid larvae and to larval characters of representatives of other endopterygote lineages. Characters potentially relevant for phylogenetic reconstruction are listed and discussed. The larvae of Raphidioptera differ distinctly from other neuropterid larvae in their morphology. They are mainly characterised by autapomorphic and plesiomorphic character states and few features indicate systematic affinities with other groups. Endopterygote groundplan features maintained in Raphidioptera are the complete tentorium, the free labrum, the full set of labral muscles, the presence of four extrinsic antennal muscles, the three-segmented labial palpi, the presence of a full set of extrinsic maxillary and labial muscles, the presence of a salivarium, and possibly the high number of stemmata. Apomorphies likely correlated with predaceous habits are the long gula, the protracted maxillae, the longitudinal arrangement of extrinsic maxillary muscles, and the elongated prepharyngeal tube. Highly unusual, potentially autapomorphic features are the presence of a dorsal ligament of the tentorium and paired gland-like structures below the pharynx. A prognathous or very slightly inclined head and slender mandibles without mola are features shared by larvae of all orders of Neuropterida. The parallel-sided head is a potential synapomorphy of Raphidioptera and Megaloptera. A fully prognathous head with anteriorly shifted posterior tentorial grooves and the presence of a parietal ridge and a distinct neck region are features shared with Corydalidae. Characters of the larval head are not sufficient for a reliable placement of Raphidioptera.     

Functional response of suspension feeding anuran larvae to different particle sizes at low concentrations (Amphibia)

The influence of particle size, initial particle concentration and larval stage on the ingestion rate, ‘retention efficiency’, and filtering rate of anuran larvae with varying filter apparatus anatomy and different life histories was investigated for four species. Larvae of premetamorphic Stages 28 and 32 and prometamorphic Stage 40 were selected for filtering experiments on the basis of their different growth rates. Three different sizes of silica gel particles were offered as mock food. Particle concentration was measured photometrically. The Michaelis-Menten model was used to describe the dependency of ingestion rate, filtering rate, and ‘retention efficiency’ upon initial particle concentration, and to calculate maximum ingestion rate, threshold concentration, and the half-saturation constant. (1) The highest ingestion rates, filtering rates and ‘retention efficiencies’ were achieved by Xenopus laevis larvae, followed by Bufo calamita larvae. Bufo bufo larvae lay at the opposite end of the scale. Rana temporaria larvae were placed between B. calamita and B. bufo larvae. This order is attributed to differences in life histories, especially the different breeding environments in which these larvae occur. (2) The larger the particle size and the older the stage, the greater the tendency toward saturation of the ingestion rate, filtering rate and ‘retention efficiency’. These filtration parameters are graded according to particle size. The ingestion rate (number of particles), filtration rate and ‘retention efficiency’ are greatest for PS3. Ingestion volume is greatest for PS 1. The difference between PS3 and PS2 on the one hand, and PS1 on the other, is often great; for Stage 28 X. laevis it is very great. This shows that larvae ingest large particles more effectively, and that the most effective ingestion takes place at Stages 28 and 32, owing to the growth function of these stages. The ability of larvae to ingest large particles effectively is possibly a very basic phylogenetic characteristic. (3) The threshold concentration is lowest when the particles are at their largest. In accordance with conclusions drawn by other authors, threshold feeding is attributed to regulation by buccal pumping and mucus production. Considerable importance is attributed to threshold feeding with respect to larval adaptation to oligotrophic environments.     

Vergleichende Ultrastrukturuntersuchungen der Eu- und Paraspermien von 13Protodrilus-Arten (Polychaeta,Annelida) und ihre taxonomische und phylogenetische Bedeutung

The morphology of the slender, filiform spermatozoa of 13Protodrilus species of 22 different populations is investigated by light and transmission electron microscopy. All species have two types of spermatoza: fertile euspermatozoa, and paraspermatozoa, which are probably infertile and may comprise up to 20% of the total number of mature gametes. This is the first record of sperm dimorphism in polychaetes. The general construction pattern of the euspermatozoa is very complex. It shows a longish tapering acrosomal vesicle with an internal acrosomal rod, a rod-like conical nucleus, and a midpiece with numerous very complex supporting elements and two thin mitochondrial derivatives. Further, it has a ‘peribasal body’ surrounding the basal body of the axoneme, an anulus region with an ‘anchoring apparatus’ and an anulus cuff. Posteriorly, the tail region proper contains in some species 2 to 9 supporting rods. In several species the euspermatozoon shows very distinct and species-specific alternations of this ‘general pattern’ relating to e.g. size of sperm elements, structure of acrosome and nucleus, presence or absence of axial rod, and number, shape and size of supporting elements in midpiece and tail. In a number of species some sections of the euspermatozoon overlap with each other more or less strongly. The paraspermatozoon has a comparatively simple construction pattern and possesses no supporting structures in midpiece and tail region. The midpiece is very short and, in some species, entirely surrounded by its two thin and elongate mitochondrial derivatives. An axial rod is often missing or reduced; different sperm sections never overlap each other. In contrast to the euspermatozoa, the paraspermatozoa of the different species have a very similar ultrastructure. Their possible function in spermatophore transfer and histolytical opening of the female epidermis is discussed. A comparison of the different forms of euspermatozoa inProtodrilus elucidates possible plesiomorphous and apomorphous sperm traits. Very likely, the hypothetical plesiomorphous type of spermatozoa inProtodrilus has a very similar morphology to that of the paraspermatozoa, which for this reason are considered to be a sort of persisting representatives of the ancientProtodrilus sperm type. InProtodrilus, the different traits of the euspermatozoa represent excellent taxonomic characters for distinguishing species (e.g. ‘sibling species’). They can also be used well for phylogenetics within the genus, whereas the relations ofProtodrilus to other polychaete groups cannot be clarified solely on the basis of sperm characters, since in all groups the sperm structure is primarily an adaptation to a specific mode of reproduction. Generally, the value of sperm characters in phylogenetic considerations at higher taxonomic levels seems to be very limited due to the surprisingly wide range of different sperm structures within a single genus as is demonstrated in the present paper.      

Sexual Selection,Ontogenetic Acceleration,and Hypermorphosis Generates Male Trimorphism in Wellington Tree Weta

Strong sex-specific selection on traits common to both sexes typically results in sexual dimorphism. Here we find that Wellington tree weta (Hemideina crassidens) are sexually dimorphic in both head shape and size due to differential selection pressures on the sexes: males use their heads in male-male combat and feeding whereas females use theirs for feeding only. Remarkably, the sexes share a common ontogenetic trajectory with respect to head growth. Male head shape allometry is an extension of the female’s trajectory despite maturing two instars earlier, a feat achieved through ontogenetic acceleration and hypermorphosis. Strong sexual selection also favours the evolution of alternative reproductive strategies in which some males produce morphologically different weapons. Wild-caught male H. crassidens are trimorphic with regard to weapon size, a rare phenomenon in nature, and weapon shape is related to each morph’s putative mating strategy.     

Phylogenetic Relationships of the Suborders of Coleoptera (Insecta)

One hundred seven external and internal characters of larval and adult representatives of 28 genera of the coleopteran suborders were analyzed cladistically. Four groups of Neuropterida were introduced as outgroup. The analysis yielded 18 trees with a minimum of 194 steps (CI 0.691). All trees support the monophyly of all four suborders and a branching pattern (Archostemata + (Adephaga + (Myxophaga + Polyphaga))). The presence of elytra with meso- and metathoracic locking devices, the specific hind-wing folding, the close connection of exposed sclerites, the absence of the mera, the absence of eight thoracic muscles, the reduced abdominal sternite I, and the invagination of terminal segments are autapomorphies of Coleoptera. The monophyly of Coleoptera excl. Archostemata is supported by further transformations of the thoracic sclerites such as absence of the mesothoracic discriminal line and katepisternal joint, by an internalized or absent metathoracic trochantin, by the presence of a bending zone in the hind-wing, and by eight further muscle losses. Fusion of tibia and tarsus and presence of a single claw are larval synapomorphies of Myxophaga and Polyphaga. Adults are characterized by fusion of protrochantin and propleura and by the rigid connection of the meso- and metathoracic ventrites. The eucinetoid lineage of Polyphaga is characterized by the secondary absence of the bending zone of the alae. This results in a distinctly simplified wing folding mechanism. The monophyly of Cucujiformia (+ Bostrichoidea) is supported by the presence of cryptonephric Malpighian tubules. Transformations of fore-and hind-wings, reinforcement and simplification of the thoracic exoskeleton, and an efficient use of a distinctly reduced set of thoracic muscles play an important role in the early evolution of Coleoptera. Many different larval character transformations take place in the earlier Mesozoic within the suborders.     

Das Prothorakalskelett vonAtractocerus (Lymexylonidae) und seine Bedeutung für die Phylogenie der Coleopteren,besonders der Polyphagen (Insecta: Coleoptera)

Zusammenfassung Das Prothorakalskelett vonAtractocerus (Lymexylonidae) wird untersucht. In der sogenannten Praecoxalbrücke ist das Anepisternum durch eine als Anapleuralnaht gedeutete Furche abgeteilt. Au\erdem ist caudal ein sternaler Bereich (Basisternum und Furcasternum) abgegliedert.Die Trochantinopleura ist durch eine Naht (Pleuralnaht) in Epimeron und Katepisternum + Trochantinus unterteilt.Die Trochantinopleura samt der Coxa ist nur durch eine Membran mit dem Tergum verbunden, spezielle Gelenkstrukturen fehlen in beiden Skleriten. Die Cryptopleura ist daher weniger entwickelt als bei sonstigen Polyphagen.Ein sehr gut skierotisiertes, ausgedehntes Spinasternum ist vorhanden, au\erdem treten je zwei gro\e Postpleuralsklerite auf.Im Halsbereich findet sich au\er den Laterocervicalia jederseits ein gro\es dorsales Cervicale.Im Prothorakalbereichvon Atractocerus ist folglich eine Reihe von Strukturen erhalten und erkennbar, die bei den übrigen Coleoptera (auch bei Adephaga und Cupedidae) verschwunden sind. Die aufgefundenen VerhÄltnisse werden als sehr ursprünglich für die Polyphaga angesehen.Daher wird vermutet, da\ der ursprüngliche Prothorax der Polyphaga dem der Neuropteria sehr Ähnlich war, nÄmlich eine wenig verfestigte Pleura, die mit dem Tergum nur in lockerer Verbindung stand und distal freie und frei bewegliche Coxae besa\. Der ursprüngliche Polyphagenprothorax kommt demnach dem Grundplan des Holometabolenprothorax sehr nahe.Angesichts der Ursprünglichkeit des Polyphagenprothorax wird die Hypothese eines SchwestergruppenverhÄltnisses zwischen Coleoptera und allen übrigen Holometabola erneut zur Diskussion gestellt.Es wird die Ansicht vertreten, der Polyphagenprothorax sei gegenüber dem Prothorax der Adephaga und Cupedidae in vielen Merkmalen plesiomorph. Daher wird die Möglichkeit erwogen, da\ Cupedidae und Adephaga in einem engeren VerwandtschaftsverhÄltnis zueinander stehen als jede dieser Gruppen zu den Polyphagen.Die Stellung der Myxophaga wird diskutiert, kann jedoch zur Zeit nicht entschieden werden. Es wird die Möglichkeit erwogen, da\ die Myxophaga den Adephaga und Cupedidae verwandtschaftlich nÄher stehen als den Polyphaga, sofern die Myxophaga überhaupt eine monophyletische Einheit bilden.

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The prothoracic skeleton ofAtractocerus (Lymexylonidae) and its significance for the phylogeny of Coleoptera, especially of polyphaga (Insecta: Coleoptera)

Summary The prothoracic skeleton ofAtractocerus (Lymexylonidae) is described. In the so-called precoxal bridge the anepisternum is separated by a suture which is recognized as anapleural suture. In the caudal part of the precoxal bridge a sternal plate (basisternum and furcasternum) is separated.The trochantinopleural plate is divided by a pleural suture in epimeron and katepisternum + trochantin.The connexion of trochantinopleura and tergum is only membranous. Specialized joint structures are absent in both sclerites. The cryptopleural invagination is not as much developed as in other Polyphaga.A fairly well sclerotized and large spinasternal plate exists. Two large laterospinae are present on both sides.In the cervical region a large dorsal cervical sclerite and two lateral cervical sclerites are to be found on both sides.Some structures are recognizable in the porthoracic region ofAtractocerus which have been lost in other Coleoptera (also in Adephaga and Cupedidae). Conditions as seenm Atractocerus are believed to be very primitive among Polyphaga.Hence it is supposed, that the original prothorax of Polyphaga has been very alike the neuropterian one in possessing a pleura, membranous over lager areas, the connexion of which to the tergum was not solid. The coxae are supposed to have been free distal being able to free movement. The most primitive polyphagous prothorax is believed to come very close to the generalized prothorax of the holometabolous insects.Concerning the primitiveness of the polyphagous prothorax the hypothesis of a sister-group relation of Coleoptera and the remaining Holometabola is discussed once more.The highly plesiomorphic status of the polyphagous prothorax as compared with the prothorax of Adephaga and Cupedidae is stressed. For this reason it is considered that Cupedidae and Adephaga might be more closely related to each other, than either to the Polyphaga.The position of the Myxophaga is discussed, but is not possible to decide at present. A closer relation of the Myxophaga to Adephaga and Cupedidae than to Polyphaga is taken into consideration. It is not shure at all, however, whether the Myxophaga constitute a monophyletic group.

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Abkürzungen Aes Anepisternum - Apl Anapleuralnaht - Cpl Cryptopleura - Cx Coxa - DCv Dorsales Cervicale - Em Epimeron - Fu Furcaleinstülpung - Kes Katepisternum - LCv Laterales Cervicale - M Ansatz der Membran zwischen Pronotum und Trochantinopleura - Pl-cx Pleurocoxalgelenk - Pln Pleuralnaht - Pn Pronotum - Pps Postpleuralsklerit - Prs Praeepisternum - Sp Spinasternum - Spl Sternopleuralnaht - St Sternum - Stg Stigma - Ti Trochantinus - Ti-cx Trochantinocoxalgelenk     

Food spectra of the farm juveniles of the Chum Salmon <Emphasis Type="Italic">Oncorhynchus keta</Emphasis> (Salmoniformes,Salmonidae) in the Ryazanovka River (Southern Primor’e)

Qualitative data are presented on the diet of juvenile chum salmon Oncorhynchus keta released from the Ryazanovka experimental fish hatchery farm situated in the south of Primor’e Territory. The stomach fullness, frequency of occurrence of food items, their average weight value, and selectivity are estimated. Food spectra of chum salmon juveniles during downstream migration comprised representatives of 51 taxa of bottom freshwater invertebrates and terrestrial insects. The bulk of the diet consisted of larvae of aquatic insects—chironomids, other Diptera, and mayflies. Their diversity increased with the growth of fry. Fry of chum salmon had a wide spectrum of feeding preference, favorite food items were larvae and pupae of chironomids.     

Food habits of wolves in central Italy based on stomach and intestine analyses

We investigated wolfCanis lupus Linnaeus, 1758 food habits in central Italy by examining stomach and/or intestine contents of 59 individuals. Road accident and illegal kills were main causes of the wolves’ death. Ungulates represented the bulk of the diet (55% in frequency), and among them wild boar was the most important prey, followed by domestic Caprinae. Food items of domestic origin accounted for about 1/3 of all the diet. Diet composition did not vary between stomachs and intestines in spite of the higher degree of digestion of the intestines’ contents. The frequent detection of numerous larvae of Diptera and/or necrophagous Coleoptera, let suppose the consumption of already dead animals, and suggests a general underestimate of the wolf’s scavenging behaviour in previous studies based on scat analyses.     

Polyèdres du CPV d’Euxoa scandens [Lep.: Noctuidae] produitsin vivo et sur cellules cultivéesin vitro Études comparatives

Résumé Les polyèdres produits dans les cellules deLymantria dispar L. cultivéesin vitro, après infection par le virus de la polyédrose cytoplasmique d’Euxoa scandens Riley sont de forme exclusivement cubique. Par contre, les formes parasphériques sont rencontrées en très grande majorité lors de l’infection des larves d’E. scandens. La forme cubique se maintient en culture cellulaire après plusieurs passages du virus alors que les polyèdres extraits des cellules infectéesin vitro induisent à nouveauin vivo des inclusions virales de forme hétérogène. Les polyèdres provenent d’un 1^er passage du virusin vitro dans des cellules différentes de celles de l’h?te d’origine entra?nent chez ce dernier une infection causant avec une intensité égle des effets caractéristiques d’une polyédrose cytoplasmique. Néanmoins, les taux d’infection larvaire sont inférieurs à ceux causés par les polyèdres produitsin vivo.

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Summary Cytoplasmic polyhedra first isolated from the larvae ofEuxoa scandens are heterogenous in shape (more than 99% spheric, less than 1% cubic). The non occluded or occluded viruses extracted from infected midgut induce polyhedra, exclusively cubical in shape, inLymantria dispar cells cultivatedin vitro. This shape is maintained after passages of the virus in these cells. Reinfection of the larvae by the polyhedra producedin vitro is characterized by the reapparition of the heterogenous in shape polyhedra. Inclusion bodies synthetized after a 1 st passage of CPVin vitro are less infectious to the original host according to the number of infected larvae. But on the other hand, the physiological effects on the insect of an infection by a cytoplasmic polyhedrosis virus are similar by using either thein vivo orin vitro produced polyhedra.

     

Ocellar atavism in Coleoptera: plesiomorphy or apomorphy?

Ocelli and ocellus‐like structures on the vertex of the adult head were examined in different representatives of Coleoptera and the presence of these was confirmed for the suborder Polyphaga. The presence of structures, which are likely homologous with ocelli of other insects were confirmed by semi‐thin sectioning in Hydraenidae, Staphylinidae, Derodontidae and Dermestidae. The presence of ocelli is newly recorded for a representative of Scydmaenidae (Nesuthia fijii Franz). The weakly pigmented areas on the vertex of Neopelatops (Leiodidae) lack a lens and associated nervous tissue and are referred to as pseudocelli, which may be present in other groups. The internal structure of Coleopteran ocelli is strongly simplified compared with other groups of Insecta where longitudinal retinula cells are arranged at a right angle to the cuticular surface and enclosed by a sheath of pigment cells. Such a regular arrangement is absent from all beetles examined histologically. A flattened group of cells without a rhabdom and without an enclosing layer of pigment cells is present underneath the cuticular lens. While, the infrastructure of the ocelli is more or less reduced in Coleoptera, the presence of these features in the ground‐plan of Coleoptera is dependent on the confirmation of the presence of ocelli in Archostemata (Jurodidae?) and a robust phylogenetic hypothesis for the order.     

On the head morphology of Tetraphalerus, the phylogeny of Archostemata and the basal branching events in Coleoptera

Internal and external features of Tetraphalerus bruchi were studied using X‐ray microtomography (µ‐CT) and other techniques, and head structures were described in detail. µ‐Ct is highly efficient for the assessment of anatomical data. A data matrix with 90 morphological characters of recent and fossil beetles was analyzed with different approaches (parsimony, Bayesian analysis). The results of the parsimony analysis resulted in the following branching pattern: (?Tshekardocoleidae + (?Permocupedidae, ?Rhombocoleidae + (?Triadocupedidae + ((Adephaga + (Myxophaga + Polyphaga))) + Archostemata s.str. [including Jurodidae]))). Sikhotealinia is placed as sister group of ?Jurodes (Jurodidae), and Jurodidae as sister group of the remaining Archostemata (Bayesian analysis) or of a clade comprising Micromalthidae, Crowsoniellidae, ?Ademosynidae, ?Schizophoridae and ?Catiniidae. The monophyly of Ommatidae and Cupedidae is well supported and Priacma is placed as the sister group of all other Cupedidae. Important events in the early evolution of Coleoptera are the shortening of the elytra and the transformation of the elytral venation (Coleoptera excluding ?Tshekardocoleidae), the formation of a closed subelytral space (Coleoptera excluding ?Tshekardocoleidae and ?Permocupedidae), the reduction of two apical antennomeres, and the loss of the broad prothoracic postcoxal bridge (Coleoptera excluding ?Tshekardocoleidae, ?Permocupedidae and ?Rhombocoleidae). Plesiomorphic features preserved in extant Archostemata are the tuberculate cuticle, the elytral pattern with parallel longitudinal ribs and window punctures, a mesoventrite with a transverse ridge, triangular mesocoxae with a distinct meron, and the exposed metatrochantin. The fossils included in the analyses do not only contribute to the reconstruction of character evolution but also influence the branching pattern. An understanding of the major evolutionary events in Coleoptera would not be possible without considering the rich fossil record of Permian and Mesozoic beetles. © The Willi Hennig Society 2007.     

Extremely miniaturised and highly complex: The thoracic morphology of the first instar larva of Mengenilla chobauti (Insecta,Strepsiptera)

Thoracic structures of the extremely small first instar larva of the strepsipteran species Mengenilla chobauti (ca. 200 μm) were examined, described and reconstructed 3-dimensionally. The focus is on the skeletomuscular system. The characters were compared to conditions found in other insect larvae of very small (Ptiliidae) or large (Dytiscus) size (both Coleoptera) and features of “triungulin” larvae, first instar larvae of Rhipiphoridae, Meloidae (both Coleoptera), and Mantispidae (Neuroptera).The specific lifestyle and the extreme degree of miniaturisation result in numerous thoracic modifications. Many sclerites of the exo- and endoskeleton are reduced. Cervical sclerites, pleural ridges, furcae and spinae are absent. Most of the longitudinal muscles are connected within the thorax, and a pair of ventral longitudinal muscles is present in the pleural region of the meso- and metathorax. This results in a high intersegmental flexibility. Due to the size reduction and the correlated shift of the brain to the thorax, with 94 identified muscles the thoracic musculature appears highly compact. Compared to larger larvae the number of both the individual muscles and the muscle bundles are distinctly reduced. The thorax of the first instar larvae displays many additional strepsipteran autapomorphies. At least partly due to the highly specialised condition, potential synapomorphies with other groups were not found.