Patterns of morphological simplification and innovation in the megadiverse Holometabola (Insecta).

We analyzed patterns of complexity and simplicity in holometabolan insects using parsimony and maximum-likelihood. By contrast with other groups of arthropods (and most other groups of animals), insects have undergone a stepwise process of structural simplification in their evolution. The megadiverse Holometabola are characterized mainly by structurally simplified larvae, which differ strongly from the adults in their morphology and usually also in their life habits. Although smaller groups such as Neuropterida have largely maintained their structural complexity in adults and immature life stages, a series of reductions occurred with the appearance and diversification of Coleopterida, Mecopterida and especially Antliophora. Parasitic Strepsiptera or fleas display conspicuous patterns of reduction in different life stages and body regions, and high degrees of simplification also occur in groups with short-lived adults. Larvae living in moist substrates display far-reaching structural simplifications and also morphological uniformity, especially in the species-rich Diptera, but also in other groups. Liquid feeding leads to correlated simplifications and innovation of adult head structures, especially of the mouthparts. Functional or anatomical dipterism leads to an optimization of the flight apparatus in most holometabolous groups, which is correlated with reductions in one of the pterothoracic segments, and coupled (e.g. by hamuli), partly reduced or transformed wings (e.g. halteres). In flightless groups, the pterothoracic skeleto-muscular apparatus is strongly simplified. In the abdomen of adult females a stepwise reduction of the lepismatoid ovipositor occurs. By contrast, the male genital apparatus often undergoes an extreme diversification. Our evaluations revealed a highly correlated complexity between larval and adult stages.

Evolution of cephalic structures in extreme myrmecophiles: a lesson from Clavigeritae (Coleoptera: Staphylinidae: Pselaphinae).

Pselaphinae is a large subfamily, comprising over 10 000 species of the megadiverse Staphylinidae (rove beetles). A remarkable feature of this group is the extreme structural diversity of different body regions, especially the head and its appendages. Within Pselaphinae, Clavigeritae stand out as a clade of highly specialized myrmecophiles. We examined internal and external head structures of the clavigerite species Diartiger kubotai Nomura, using state-of-the-art techniques. The cephalic morphology indicates in a phylogenetic context that the loss of eyes in some Clavigeritae was the latest of major evolutionary changes. We compiled the largest set of morphological data ever scored for the subfamily, comprising 155 characters of the head. Parsimony analyses and Bayesian inference yielded a similar phylogenetic pattern, largely congruent with results published previously. We retrieved Pselaphinae as a clade, and Faronitae as sister to all remaining groups of the subfamily. Faronitae are followed by a "Euplectitae grade" and non-monophyletic Goniaceritae, Batrisitae and Pselaphitae. Clavigeritae are monophyletic, but have evolved within the pselaphite grade. The enigmatic Colilodion Besuchet, recently shifted from Clavigeritae to a paraphyletic Pselaphitae, was placed as sister to extant clavigerites based on an array of cephalic synapomorphies. The current classification of Pselaphinae is unstable and deep changes should be made maintaining only monophyletic units, whereas most of the supertribes are paraphyletic. Characters of the head, with a concentration of mouthparts and sensory structures, and essential parts of the digestive tract and the nervous system, are highly informative phylogenetically. Study of internal structures, presently still at a very preliminary stage, obviously is essential for understanding the evolution of Pselaphinae. Future genetic investigations may reveal mechanisms behind the unique structural megadiversity in this exceptional group of rove beetles.

Structure and Evolution of Insect Sperm: New Interpretations in the Age of Phylogenomics.

This comprehensive review of the structure of sperm in all orders of insects evaluates phylogenetic implications, with the background of a phylogeny based on transcriptomes. Sperm characters strongly support several major branches of the phylogeny of insects-for instance, Cercophora, Dicondylia, and Psocodea-and also different infraordinal groups. Some closely related taxa, such as Trichoptera and Lepidoptera (Amphiesmenoptera), differ greatly in sperm structure. Sperm characters are very conservative in some groups (Heteroptera, Odonata) but highly variable in others, including Zoraptera, a small and morphologically uniform group with a tremendously accelerated rate of sperm evolution. Unusual patterns such as sperm dimorphism, the formation of bundles, or aflagellate and immotile sperm have evolved independently in several groups.

The larvae of Altica koreana (Ogloblin) and A. viridicyanea (Baly) (Coleoptera: Chrysomelidae: Galerucinae: Alticini).

The first instar and mature larvae of Altica koreana (Ogloblin) and A. viridicyanea (Baly) are described and illustrated for the first time and compared with larvae of Altica caerulescens (Baly), A. cirsicola Ohno, and A. fragariae (Nakane). A key to the five related Altica species is also given.

The thoracic anatomy of Pselaphus heisei (Pselaphinae, Staphylinidae, Coleoptera).

We document external and internal thoracic structures of the free-living pselaphine beetle Pselaphus heisei (Pselaphitae) using a set of traditional and modern techniques. Like in the specialized myrmecophile Claviger testaceus (Clavigeritae), the skeletal elements of the pro- and pterothorax are highly compact, with largely reduced inter- and intrasegmental sutures. Features previously listed as synapomorphies of staphylinid subgroups, to which Pselaphinae belong, are confirmed for P. heisei. The only previously proposed thoracic synapomorphy of Pselaphinae, the mesoventral foveae, is likely transformed in P. heisei: we assume that the concavities are directed mesad and internally fused, thus forming a broad channel ("perforation") extending through the keel-like median region of the mesoventrite. The prothoracic foveal system is strongly reduced, with only one pair of pits present in front of the procoxae. Their internal invaginations form a transverse ventral endoskeletal bar that stabilizes the prothorax. The condition observed in the free-living P. heisei is in contrast with previous hypotheses linking the reduction of the foveal system with myrmecophily. Moreover, traces of the mesoventral foveae are even preserved in the highly specialized inquiline C. testaceus. Gland cells are associated with areas of hyaline squamose setae on different body regions, suggesting release of secretions on the ventral side of the head, pro- and mesothorax, and abdominal base. Similar specialized setal patches are common in Pselaphini and related groups within Pselaphitae. The prothoracic musculature in P. heisei is more complex than that in the myrmecophilous C. testaceus and the free-living, unspecialized Creophilus maxillosus (Staphylininae). The metathoracic muscle system is strongly simplified, demonstrating that P. heisei cannot fly, even though wings, some skeletal elements of the flight apparatus, and some small direct flight muscles are preserved. It cannot be fully excluded that indirect flight muscles and thus a functional flight apparatus is preserved in a certain percentage of individuals.

Have female twisted-wing parasites (Insecta: Strepsiptera) evolved tolerance traits as response to traumatic penetration?

Traumatic insemination describes an unusual form of mating during which a male penetrates the body wall of its female partner to inject sperm. Females unable to prevent traumatic insemination have been predicted to develop either traits of tolerance or of resistance, both reducing the fitness costs associated with the male-inflicted injury. The evolution of tolerance traits has previously been suggested for the bed bug. Here we present data suggesting that tolerance traits also evolved in females of the twisted-wing parasite species Stylops ovinae and Xenos vesparum. Using micro-indentation experiments and confocal laser scanning microscopy, we found that females of both investigated species possess a uniform resilin-rich integument that is notably thicker at penetration sites than at control sites. As the thickened cuticle does not seem to hamper penetration by males, we hypothesise that thickening of the cuticle resulted in reduced penetration damage and loss of haemolymph and in improved wound sealing. To evaluate the evolutionary relevance of the Stylops-specific paragenital organ and penis shape variation in the context of inter- and intraspecific competition, we conducted attraction and interspecific mating experiments, as well as a geometric-morphometric analysis of S. ovinae and X. vesparum penises. We found that S. ovinae females indeed attract sympatrically distributed congeneric males. However, only conspecific males were able to mate. In contrast, we did not observe any heterospecific male attraction by Xenos females. We therefore hypothesise that the paragenital organ in the genus Stylops represents a prezygotic mating barrier that prevents heterospecific matings.

In the twilight zone-The head morphology of Bergrothia saulcyi (Pselaphinae, Staphylinidae, Coleoptera), a beetle with adaptations to endogean life but living in leaf litter.

The pselaphine Bergrothia saulcyi shows features seemingly linked with life in deep soil layers, such as greatly reduced and non-functional compound eyes, a sensorium of long tactile setae, long appendages, and flightlessness. However, the tiny beetles occur in forest leaf litter, together with a community of beetles with wings and well-developed eyes. We hypothesize that B. saulcyi moves into deep soil under dry conditions, and returns to upper layers when humidity increases again. Despite the evolutionary cost of a reduced dispersal capacity, this life strategy may be more efficient and less hazardous than moving to different habitats using flight and the visual sense in an environment periodically drying out. We also discuss cephalic features with potential phylogenetic relevance. Plesiomorphies of B. saulcyi include the presence of anterior tentorial arms, well-developed labral retractors, and a full set of extrinsic maxillary and premental muscles. Apomorphic cephalic features support clades Protopselaphinae + Pselaphinae, and Pselaphinae. A conspicuous derived condition, the clypeo-ocular carina, is a possible synapomorphy of Batrisitae and genera assigned to Goniaceritae. A complex triple set of cephalic glands found in B. saulcyi is similar to a complex identified in the strict myrmecophile Claviger testaceus (Clavigeritae). It is conceivable that glands linked with food uptake in free-living pselaphines were genetically re-programmed in ancestors of inquilines, to enable them to appease the host ants. We suggest that behavioral studies are necessary to understand the poorly known life habits of B. saulcyi. Additional information is required to explain why a species with irreversibly reduced visual sense and other adaptations typical of endogean or cave-dwelling beetles was only collected from the upper leaf litter layer.

Anatomy and evolution of the head of Dorylus helvolus (Formicidae: Dorylinae): Patterns of sex- and caste-limited traits in the sausagefly and the driver ant.

Ants are highly polyphenic Hymenoptera, with at least three distinct adult forms in the vast majority of species. Their sexual dimorphism, however, is overlooked to the point of being a nearly forgotten phenomenon. Using a multimodal approach, we interrogate the near total head microanatomy of the male of Dorylus helvolus, the "sausagefly," and compare it with the conspecific or near-conspecific female castes, the "driver ants." We found that no specific features were shared uniquely between the workers and males to the exclusion of the queens, indicating independence of male and worker development; males and queens, however, uniquely shared several features. Certain previous generalizations about ant sexual dimorphism are confirmed, while we also discover discrete muscular presences and absences, for which reason we provide a coarse characterization of functional morphology. Based on the unexpected retention of a medial carinate line on the structurally simplified mandible of the male, we postulate a series of developmental processes to explain the patterning of ant mandibles. We invoke functional and anatomical principles to classify sensilla. Critically, we observe an inversion of the expected pattern of male-queen mandible development: male Dorylus mandibles are extremely large while queen mandibles are poorly developed. To explain this, we posit that the reproductive-limited mandible phenotype is canalized in Dorylus, thus partially decoupling the queen and worker castes. We discuss alternative hypotheses and provide further comparisons to understand mandibular evolution in army ants. Furthermore, we hypothesize that the expression of the falcate phenotype in the queen is coincidental, that is, a "spandrel," and that the form of male mandibles is also generally coincidental across the ants. We conclude that the theory of ant development and evolution is incomplete without consideration of the male system, and we call for focused study of male anatomy and morphogenesis, and of trait limitation across all castes.

Profound head modifications in Claviger testaceus (Pselaphinae, Staphylinidae, Coleoptera) facilitate integration into communities of ants.

Clavigeritae is a group of obligate myrmecophiles of the rove beetle subfamily Pselaphinae (Staphylinidae). Some are blind and wingless, and all are believed to depend on ant hosts through feeding by trophallaxis. Phylogenetic hypotheses suggest that their ancestors, as are most pselaphines today, were free-living predators. Morphological alterations required to transform such beetles into extreme myrmecophiles were poorly understood. By studying the cephalic morphology of Claviger testaceus, we demonstrate that profound changes in all mouthpart components took place during this process, with a highly unusual connection of the maxillae to the hypopharynx, and formation of a uniquely transformed labium with a vestigial prementum. The primary sensory function of the modified maxillary and labial palps is reduced, and the ventral mouthparts transformed into a licking/'sponging' device. Many muscles have been reduced, in relation to the coleopteran groundplan or other staphylinoids. The head capsule contains voluminous glands whose appeasement secretions are crucial for the beetle survival in ant colonies. The brain, in turn, has been shifted into the neck region. The prepharyngeal dilator is composed of an entire series of bundles. However, the pharynx does not show any peculiar adaptations to taking up liquid food. We demonstrate that far-reaching cephalic modifications characterize C. testaceus, and that the development of appeasement glands and adaptation of the mouthparts to trophallaxis determine the head architecture of this extreme myrmecophile.

Distal leg structures of the Aculeata (Hymenoptera): A comparative evolutionary study of Sceliphron (Sphecidae) and Formica (Formicidae).

The distal parts of the legs of Sceliphron caementarium (Sphecidae) and Formica rufa (Formicidae) are documented and discussed with respect to phylogenetic and functional aspects. The prolegs of Hymenoptera offer an array of evolutionary novelties, mainly linked with two functional syndromes, walking efficiently on different substrates and cleaning the body surface. The protibial-probasitarsomeral cleaning device is almost always well-developed. A complex evolutionary innovation is a triple set of tarsal and pretarsal attachment devices, including tarsal plantulae, probasitarsomeral spatulate setae, and an arolium with an internal spring-like arcus, a dorsal manubrium, and a ventral planta. The probasitarsal adhesive sole and a complex arolium are almost always preserved, whereas the plantulae are often missing. Sceliphron has retained most hymenopteran ground plan features of the legs, and also Formica, even though the adhesive apparatus of Formicidae shows some modifications, likely linked to ground-oriented habits of most ants. Plantulae are always absent in extant ants, and the arolium is often reduced in size, and sometimes vestigial. The arolium contains resilin in both examined species. Additionally, resilin enriched regions are also present in the antenna cleaners of both species, although they differ in which of the involved structures is more flexible, the calcar in Sceliphron and the basitarsal comb in Formica. Functionally, the hymenopteran distal leg combines (a) interlocking mechanisms (claws, spine-like setae) and (b) adhesion mechanisms (plantulae, arolium). On rough substrate, claws and spine-like setae interlock with asperities and secure a firm grip, whereas the unfolding arolium generates adhesive contact on smooth surfaces. Differences of the folded arolium of Sceliphron and Formica probably correlate with differences in the mechanism of folding/unfolding.

†Bittacopsocus-a new bizarre genus of †Permopsocida (Insecta) from Burmese Cretaceous amber.

A new insect species (†Bittacopsocus megacephalus Beutel, Prokop, Müller et Pohl gen. et sp. nov.) is described, based on a single small male (ca. 2.5 mm) embedded in mid Cretaceous Burmese amber. The species shows some resemblance with the mecopteran family Bittacidae, mainly due to strongly elongated and thin legs. However, the structural affinities are apparently due to convergency. Different features, but especially the mouthparts and the pattern of wing venation, indicate that the species belongs to the extinct order †Permopsocida (?Archipsyllidae). However, it differs markedly from all species previously described in this extinct group. The very thin and strongly elongated legs are probably autapomorphic. A very unusual feature is the antenna with only seven segments and extremely elongated flagellomeres. The two pairs of wings are unusually narrow. M and CuA are basally fused. Proximal rows of spines, two series of closed cells, and a distinctly increased number of terminal branches of M are present in the forewings, in contrast to other archipsyllid genera. It is conceivable that Bittacopsocus megacephalus used its long legs to rest suspended in the vegetation like Bittacus. The head structures tentatively suggest predatory behavior but the feeding habits are unclarified yet.

The thoracic morphology of the troglobiontic cholevine species Troglocharinus ferreri (Coleoptera, Leiodidae).

The thoracic morphology of the troglobiontic leiodid species Troglocharinus ferreri (Cholevinae, Leptodirini) is described and documented in detail. The features are mainly discussed with respect to modifications linked with subterranean habits. Troglocharinus is assigned to the moderately modified pholeuonoid morphotype. The body is elongated and slender compared to epigean leiodids and also cave-dwelling species of Ptomaphagini. The legs are elongated, especially the hindlegs, though to a lesser degree than in the most advanced troglobiontic species. The prothorax is moderately elongated but otherwise largely unmodified. Its muscular system is strongly developed, with more muscle bundles that in free-living staphylinoid or hydrophiloid species. The pterothorax is greatly modified, especially the metathoracic flight apparatus. The meso- and metathoracic elements of the elytral locking device are well-developed, whereas the other notal parts are largely reduced. The mesonotum is simplified, with the triangular scutellar shield as the only distinctly developed part. The mesothoracic musculature is strongly reduced, with only 6 muscles compared to 12 or 13 in free-living staphylinoid or hydrophiloid species. The metanotum is greatly reduced, without a recognizable subdivision into prescutum scutum and scutellum. It is strongly narrowing laterally and lacks notal wing processes and other wing-related elements, but well-developed alacristae are present. The wings are reduced to small membranous flap-like structures inserted at the posterior end of the metanotum. A metapostnotum is not developed. Like in the case of the head, cave dwelling species of the related Ptomaphagini and Leptodirini show different trends of adaptations, with a compact ovoid or navicular body shape in the former, and a distinct trend towards elongation of the body and appendages in the latter tribe. Structural affinities of the thoraces of T. ferreri and the troglobiontic trechine carabid Sinaphaenops wangorum are mainly due to the reduced flight apparatus. The degree of muscle reduction in the pterothorax is very similar in both species.

The evolution of Strepsiptera (Hexapoda).

An evolutionary scenario for the enigmatic group Strepsiptera is provided, based on the results of a comprehensive cladistic analysis of characters of all life stages. A recently described fossil--+Protoxenos janzeni--the most archaic strepsipteran, sheds new light on the early evolution of the group and reduces the "morphological gap" between Strepsiptera and other insects. It weakens both current hypotheses--Coleoptera+Strepsiptera and Diptera+Strepsiptera (="Halteria"). The splitting into +Protoxenos (Protoxenidae) and the remaining Strepsiptera was linked with a distinct size reduction and many morphological changes. Unlike males of extant strepsipteran species, +Protoxenos was still able to process food. Mengeidae (+Mengea), with two small species, is the sister group of extant Strepsiptera. A unique characteristic of extant males (Strepsiptera s. str.) is the mouthfield sclerite. It is part of an air uptake apparatus which belongs to an extremely modified air-filled "balloon gut". Besides this, male strepsipterans possess specialised antennae and compound eyes, a strongly developed flight apparatus, large testes, and a sperm pump, whereas other organ systems are strongly reduced (e.g., fat body, malpighian tubules). Males are designed to find females within a few hours and to copulate. A dramatic change is linked with the split into Mengenillidae and Stylopidia. The change to pterygote hosts and the permanent endoparasitism of the females are evolutionary novelties acquired by the latter clade, and linked with far-reaching morphological transformations, e.g. the presence of unique brood organs. Hairy tarsal adhesive devices are present in males and guarantee efficient attachment to the host during copulation. A well-founded clade within Stylopidia is Stylopiformia, which are characterised by a unique fissure-shaped birth opening. The evolutionary development towards the most specialised and successful forms (parasites of aculeate Hymenoptera [e.g., Xenidae+Stylopidae], ca. 46% of the species) is a stepwise process. The presented evolutionary scenario comprises a complex network of functionally correlated morphological changes in primary larvae, secondary larvae, females and males.

A New Cretaceous Insect with a Unique Cephalo-thoracic Scissor Device.

Insects use different parts of their body to cling to mating partners, to catch prey, or to defend themselves, in most cases the mouthparts or the legs. However, in 400 million years of evolution [1, 2], specialized devices were independently acquired in several groups to adopt these tasks, as for instance modified legs in mantids, assassin bugs or stick insects [3-5], or clasping antennae of the globular springtails [6]. So far, no known species used the neck region between the head and thorax in one of these functional contexts. Here we describe females of †Caputoraptor elegans, a very unusual, presumably predacious insect discovered in approximately 100-million-year-old [7] Burmese amber. Based on several morphological features, we conclude that this species lived in the foliage of trees or bushes. A unique feature of the new taxon is a scissor-like mechanism formed by wing-like extensions on the posterior head and corresponding serrated edges of the dorsal sclerite of the first thoracic segment. Based on the specific structure of the apparatus, we conclude that it was probably used by females to hold on to males during copulation. A defensive or prey-catching function appears less likely. A similar mechanism did not evolve in any other known known group of extant or extinct insects.

Head capsule, chephalic central nervous system and head circulatory system of an aberrant orthopteran, Prosarthria teretrirostris (Caelifera, Hexapoda).

The head capsule, the circulatory system and the central nervous system of the head of Prosarthria teretrirostris (Proscopiidae) is described in detail, with special consideration of modifications resulting from the aberrant head shape. The transformations of the head are completely different from those found in phasmatodeans, which are also characterised by twig mimesis. The circulatory system is distinctly modified. A hitherto undescribed additional structure in the posterior head region very likely functions as a pulsatile organ. The cephalic central nervous system is strongly elongated, with changes in the position of the suboesophageal ganglion, the corpora cardiaca and the course of the nervus mandibularis. Three-dimensional reconstructions of these two organ systems in combination with the pharynx were made using Alias Maya 6.0 software. Comparisons with other representatives of Caelifera suggest a clade comprising Proscopiidae and Morabinae. The presence of a transverse muscle connecting the antennal ampullae in Prosarthria shows that this structure likely belongs to the groundplan of Orthoptera, even though it is missing in different representatives of this group. The transverse ampullary muscle is a potential synapomorphy of Orthoptera, Phasmatodea and Dictyoptera.

Head structures of males of Strepsiptera (Hexapoda) with emphasis on basal splitting events within the order.

Internal and external head structures of males of Strepsiptera were examined and the head of a species of Mengenilla is described in detail. The results suggest a reinterpretation of some structures. The head of basal extant strepsipterans is subprognathous, whereas it is strictly orthognathous in the groundplan of Strepsiptera s.l. The labrum and hypopharynx are not part of the mouthfield sclerite. The labial palps are absent in all strepsipterans. A very slightly modified mandibular articulation is preserved in Eoxenos, whereas it is distinctly reduced in other extant groups. A salivary duct, salivary glands, and a cephalic aorta are absent. The cladistic analysis of 44 characters of the head results in the following branching pattern: (Protoxenos + (Mengea + (Eoxenos + (Mengenilla [Austr.] + Mengenilla) + (Elenchus + Dundoxenos + Xenos + Stylops)))). Most apomorphies of males are associated with the necessity of finding females within a short time span and with a reduced necessity to consume food: large "raspberry" eyes, flabellate antennae with numerous dome-shaped chemoreceptors, Hofeneder's organ, an ovoid sensillum of the maxillary palp, and the simplified condition of the maxilla and the labium. Strepsiptera excl. Protoxenos are supported by the dorsomedian frontal impression, the dorsally shifted antennal insertions, a reduced number of antennal segments, absence of the galea, and probably by the presence of the mouthfield sclerite, which is a unique apomorphic feature. The balloon-gut combined with an unusual air-uptake apparatus is another possible autapomorphy of this clade. It is likely that the last common ancestor of Strepsiptera excl. Protoxenos did not process food. Strepsiptera s.str. are characterized by the strongly reduced condition of the labrum and the absence of the epistomal suture. Eoxenos is the sister group of the remaining Strepsiptera s.str. Synapomorphies of Mengenilla + Stylopidia are the advanced reduction of the mandibular articulation and the secondary absence of the ovoid sensillum. The monophyly of Mengenilla is confirmed, even though a small free labrum is present in Australian species. Derived features of Stylopidia are the absence of the coronal suture and the reduced condition of the frontal suture. Apomorphies that have evolved within Stylopidia are the membranization of parts of the head, the fusion of antennal segments, the increase or decrease of the number of flabellate flagellomeres, reductions and modifications of the mandibles, and modifications of the mouthfield sclerite. The monophyly of Stylopiformia is not unambiguously supported. A position of the mandibles posterior to the mouthfield sclerite (when adducted) is a possible synapomorphy shared by Xenos, Stylops, and other "higher Stylopidia." The blade-like distal part of the mandibles suggests a closer relationship of Elenchus with these taxa.

Comparative thoracic anatomy of the wild type and wingless (wg1cn1) mutant of Drosophila melanogaster (Diptera).

Genetically modified organisms are crucial for our understanding of gene regulatory networks, physiological processes and ontogeny. With modern molecular genetic techniques allowing the rapid generation of different Drosophila melanogaster mutants, efficient in-depth morphological investigations become an important issue. Anatomical studies can elucidate the role of certain genes in developmental processes and point out which parts of gene regulatory networks are involved in evolutionary changes of morphological structures. The wingless mutation wg1 of D. melanogaster was discovered more than 40 years ago. While early studies addressed the external phenotype of these mutants, the documentation of the internal organization was largely restricted to the prominent indirect flight muscles. We used SEM micrographs, histological serial sections, µ-computed tomography, CLSM and 3D reconstructions to study and document the thoracic skeletomuscular system of the wild type and mutant. A recently introduced nomenclature for the musculature of neopteran insects was applied to facilitate comparisons with closely or more distantly related taxa. The mutation is phenotypically mainly characterized by the absence of one or both wings and halteres. The wing is partly or entirely replaced by duplications of mesonotal structures, whereas the haltere and its associated muscles are completely absent on body sides showing the reduction. Both the direct and indirect mesothoracic flight muscles are affected by loss and reorientation of bundles or fibers. Our observations lead to the conclusion that the wingless mutation causes a homeotic transformation in the imaginal discs of wings and halteres with a direct effect on the development of skeletal structures and an indirect effect on the associated muscular system.

The phylogeny of Strepsiptera (Hexapoda).

Previous phylogenetic analyses of Strepsiptera have been limited to characters from only males or first instar larvae, and by poor taxonomic sampling. This investigation is the first cladistic analysis to use more than fourfold as many characters as any prior study, and a broader sampling of taxa. The analysis of 189 morphological characters of all stages of representatives of all extant strepsipteran families and characters of adult males of amber fossils results in the following branching pattern: (†Protoxenos+ (†Cretostylops + (†Mengea + (Mengenillidae + (Corioxenidae + (Bohartillidae + (Halictophagidae + (Elenchidae + (†Protelencholax + (Myrmecolacidae + (Callipharixenidae + (Xenidae + Stylopidae)))))))))))). The basal placement of the Baltic amber fossil †Protoxenos and the Burmese amber fossil †Cretostylops is well founded. Even though †Cretostylops is older than †Protoxenos it is almost certainly not the most basal strepsipteran group but the sister group of a clade comprising the Baltic amber fossil †Mengea + Strepsiptera s. str. (excl. stemlineage). Monophyly of Mengenillidae, Stylopidia, Stylopiformia s.l., Corioxenidae, Xenidae, and Stylopidae is confirmed. Mengenillidia is paraphyletic (with respect to †Mengea (Mengeidae)), Elenchidae (with respect to †Protelencholax) and the genus Stichotrema (with respect to the Baltic amber fossils). Thus Protelencholacidae fam. n. is described, and S. weitschati and S. triangulum are transferred to Palaeomyrmecolax. A ground plan of adult male Strepsiptera is provided and evolutionary interpretations are presented based on the obtained cladograms.

The larval head of Exechia (Mycetophilidae) and Bibio (Bibionidae) (Diptera).

Exechia and Bibio have retained several plesiomorphic groundplan features of Diptera and Bibionomorpha, including a fully exposed and sclerotized head capsule, the transverse undivided labrum, the absence of movable premandibles, and undivided mandibles without combs. The fusion of the hypostomal bridge with the head capsule and largely reduced antennae are derived features shared by both taxa. The absence of teeth at the anterior hypostomal margin is a potential autapomorphy of Bibionomorpha. A basal position of Anisopodidae is suggested by a number of plesiomorphies retained in this family. Apomorphies of Bibionomorpha excluding Anisopodidae are the reduction of tentorial elements, the partial fusion of the labrum and clypeus, one-segmented antennae, the absence of a separate submental sclerite, the loss of the labial palpus, and the reduction of the pharyngeal filter apparatus. Head structures of Bibio are largely unmodified. The subprognathous orientation is one of few autapomorphic features. In contrast, the mouthparts of Exechia are highly modified in correlation with the specialized food uptake. The rasping counterrotating movements of maxillae and mandibles with teeth oriented in opposite directions are carried out by strongly developed extensors and flexors of the paired mouthparts. The modified labium mechanically supports the "drill head" formed by the mandibles und maxillae. The necessary stability of the head capsule is provided by the hypostomal bridge which also compensates the far-reaching reduction of the tentorium.