Musculature of the Male Abdominal Segments and Terminalia in <Emphasis Type="Italic">Musca autumnalis</Emphasis> De Geer, 1776 and <Emphasis Type="Italic">Pyrellia rapax</Emphasis> (Harris, 1780) (Diptera,Muscidae: Muscini)

The structure of the abdominal and pregenital segments and genitalia of males was studied in Pyrellia rapax (Harris, 1780) and Musca autumnalis De Geer, 1776 (Muscidae, Muscini). The musculature of these species is compared with that in Musca domestica Linnaeus, 1758 (Muscidae) and Scathophaga stercoraria (Linnaeus, 1758) (Scathophagidae), previously investigated by O.G. Ovtshinnikova. Morphological analysis of sclerites and muscles of abdominal and pregenital segments and genitalia of males in Pyrellia rapax, Musca autumnalis, and M. domestica demonstrates processes of reduction in Musca as compared with P. rapax and S. stercoraria.     

Skeleton and musculature of the male genitalia in the family Nothybidae (Diptera)

Sclerites and musculature of the male genitalia of Nothybidae (Diptera) were studied for the first time. Symmetry of the genital and pregenital sclerites, similar to that in Psilidae, was revealed. The muscles of the male genitalia of Nothybus resemble the apomorphic plan of Cyclorrhapha (Sciomyzidae, Scathophagidae and Calliphoridae) due to the splitting of the hypandrium and hypandrial muscles.     

Musculature,nervous system and glands of metasomal abdominal segments of the male of Nomia melanderi Ckll. (Hymenoptera,Apoidea)

Each muscle of the third metasomal segment of the male of Nomia melanderi Ckll. is described in detail. The points of attachment of each muscle are compared with their homologs in other pregenital segments and with their homologs in the female. The function desgnated for each muscle describes its action alone or in conjunction with other muscle(s). New names are given to genital muscles by referring in the name to their points of attachment. Each intratergal muscle has homologous points of attachment in the pregenital segments of both sexes. The median tergo-dorsoplical muscle of the seventh segment and the oblique tergo-dorsoplical muscle of the eighth segment have changed their points of attachment. The intrasternal muscles are modified to suit the needs of courtship and mating, thus they are different from their homologs in the female. The spiracular muscles are well developed in all segments except the eighth, where the sterno-spiracular muscle is absent. The extrinsic genital muscles are derived from the intrasternal muscles of the eighth and ninth segments. The parameral and volsellar muscles are reduced in number. The aedeagal muscles, except the aedeago-phallic, have retained similar points of attachment to those found in primitive Hymenoptera. The topography of the metasomal nervous system is reported in detail by following each nerve and nervule to its termination. The study shows that (at least in Nomia) the criterion of nerve-concentration should not be used alone to indicate evolutionary levels. To accommodate the morphological changes in the terminal segments the Anterior and Posterior Lateral Nerves have migrated to new locations. The pattern of nerve topography (even at the nervule level) is homologous both in the different pregenital segments and between the sexes. The fact that homology does not exist between the external genitalia of the male and the modified ovipositor of the female supports the thesis that the male genital capsule is of phallic rather than prephallic origin. A pair of intersegmental membrane glands located between the seventh and eighth sterna is described. These glands may be the source of a pheromon responsible for gregariousness among “sleeping” males.     

Motor supply of the dorsal longitudinal muscles,I: homonomy and ontogeny of the motoneurones in locusts (Insecta,Caelifera)

The neural supply of the dorsal lingitudinal muscles in successive segments from the prothorax to the pregenital abdomen of adult and larval instar locusts (Locusta migratoria and Schistocerca gregaria) has been studied. Stainings have also been carried out for embryos. The whole complement consists of three muscles, of which one or both of the smaller ones degenerate in the pterothoracic segments during early imaginal life. Based on morphological criteria, several motoneurone types can be distinguished. The neural set is almost identical for all segments, independent of the general organization of each segment. At about 65% of embryogenesis, all neurone types can be identified with respect to soma position and basic features of the central branching pattern. By the end of embryogenesis, a dendritic pattern is established which resembles the adult pattern in all major aspects. The reiteration of homonomous elements suggests that they form part of the basic segmental neural Bauplan generated early in embryogenesis. This study of muscles and motoneurones forming identifiable, reiterated neuromuscular units can serve as a segmental matrix for a comparative study comprising other phylogenetic groups of the Tracheata.Abbreviations DLM dorsal longitudinal muscle - DUM dorsal unpaired median - M muscle (number) - MN motoneurone - N nerve (number)     

Phylogenetic relevance of the genital sclerites of Neuropterida (Insecta: Holometabola)

Abstract Segment 9 of male Raphidioptera, comprising tergite, sternite, gonocoxites, gonostyli and gonapophyses, is a benchmark for homologies in the male and female terminalia of the three Neuropterida orders Raphidioptera, Megaloptera and Neuroptera. The segments relating to genitalia are 9, 10 and 11 in males and 7, 8 and 9 in females. Results from holomorphological and recent molecular cladistic analyses of Neuropterida agree in supporting the sister‐group relationships between: (1) the Raphidioptera and the clade Megaloptera + Neuroptera, and (2) the suborder Nevrorthiformia and all other Neuroptera. The main discrepancy between the results of these studies is the nonmonophyly of the suborder Hemerobiiformia in the molecular analysis. The monophyly of the Megaloptera (which has been repeatedly questioned) is further corroborated by a hitherto overlooked ground pattern autapomorphy: the presence of eversible sacs within the complex of the fused gonocoxites 11 in Corydalidae and Sialidae. The recently discovered paired complex of gonocoxites 10 (parameres) in Nipponeurorthus (Nevrorthidae) indicates that the curious apex of sternite 9 of Nevrorthus and Austroneurorthus is the amalgamation of the sclerites of gonocoxites 10 with sternite 9, interpreted as synapomorphic. In the molecular study, the Nevrorthidae, Sisyridae and Osmylidae branch off in consecutive splitting events, a result that is supported by the analysis of male genital sclerites reported here. Extraordinary parallel apomorphies (e.g. excessive enlargement and modification of gonocoxites 10 ending in a thread‐like ‘penisfilum’) in derived representatives of Coniopterygidae, Berothidae, Rhachiberothidae and Mantispidae corroborate the dilarid clade of the morphological analysis and leads us to hypothesize a sister‐group relationship of the Coniopterygidae with the dilarid clade. A re‐interpretation of the tignum of Chrysopidae as gonocoxites 11 means that the structure previously called the gonarcus represents the fused gonocoxites 9. In Hemerobiidae, the corresponding sclerite is consequently also homologized as fused gonocoxites 9. The enlargement of the lateral wings of the gonocoxites in both families is interpreted as a synapomorphy. Excessive enlargement of gonostyli 11 in the Polystoechotid clade and Myrmeleontiformia supports a sister‐group relationship of these two clades. The occurrence of certain serial homologues of female genitalia structures (gonocoxites and gonapophyses), such as the digitiform processus together with the flat appendices in segment 8 of certain Myrmeleontidae, or the wart‐like processus together with the flat circular sclerites in segment 7 of certain Berothidae, as well as the presence of gonocoxites 8 as pseudosternites in certain Nemopteridae and Coniopterygidae, are probably character reversals. The digitiform processus of tergite 9 (pseudogonocoxites) in Rhachiberothidae and Austroberothella (Berothidae) are either independently developed acquisitions with a function in oviposition, or are homologous sclerites, possibly of epipleurite origin.     

Musculature, nervous system and glands of pregenital abdominal segments of the female of Nomia melanderi Ckll. (Hymenopters, Apoidea)

The gross anatomy of muscles, the topography of nerve tissues, and the histology of the pregenital abdominal glands of Nomia melanderi Ckll. are reported in detail. The movable and fixed points of muscle attachment were utilized in establishing a system of nomenclature for a typical abdominal segment. Names of nervules correspond to those of the tissues they innervate. The points of attachment of muscles of the fifth abdominal segment are essentially the same in both Nomia and Apis, except for the second tergo-sternal muscle which, in Nomia, has shifted its point of movable attachment to the membranous integument in front of the intersegmental membrane gland where it helps in relasing glandular secretion. The general plan of the nerves in the fifth abdominal segment in Nomia is more diffuse than in Apis, but there is no difficulty in establishing homology between the nervules of the two species. A pair of intersegmental stretch organs was found in abdominal segments 3–6. Glands of the sixth intersegmental membrane possess a reservoir with peripheral pouches both of which are absent in those of the fifth. Both types of glands have neither closing nor opening mechanisms, and neither is innervated. Release of glandular secretion is accomplished by the action of the tergo-sternal muscles.     

Brush-border formation in the midgut of an insect,Calliphora erythrocephala meigen

Summary The embryonic development of the brush-border of anterior midgut cells of Calliphora was studied by electron microscopy. Dense surface-forming vesicles, as described by Bonneville (1970), are found prior to microvillus formation. These dense vesicles provide membranous and coating material for the moulding of the microvilli. The number of dense vesicles increases rapidly to a maximum just before brush-border formation, after which it decreases very rapidly, accompanied by an increase in the number of microvilli. Formation of microvilli proceeds in essentially the same way as in Xenopus. First, some of the vesicles fuse with the apical cell membrane, resulting in an increase of the cell surface, part of which is coated with filamentous material deriving from the dense vesicles. This in turn leads to bulging, and short irregular microvilli appear. These are erected and elongated.Prefabricated tubular elements are believed to play a part in this erection and elongation, probably due to the unwinding of spirally coiled strands.Microvillus formation proper lasts 2 to 3 hours in Calliphora. Almost the entire amount of membranous and coating material is prefabricated prior to the formation of microvilli.     

Morphology of the abdominal skeleton and muscles of the mosquito,Culiseta inornata (Williston) (Diptera: Culicidae)

The morphology of the abdominal skeleton and muscles of the adult mosquito is incompletely known. The objectives of this study were to investigate these features in a common species, Culiseta inornata (Williston). Preserved specimens were stained lightly with methylene blue and studied with a dissecting microscope at 70 × and lower. The sclerites of the pregenital segements are best developed in segment II. The base of segment VIII in the male is narrow and semicircular in shape. This modification aids in rotation of the terminalia. Two new names are introduced for parts of the terminalia. Apodeme of sternum 9 is proposed for atrial plate of the female. Gonocoxital apodeme is a new term for a structure in the male. Both of these structures serve for attachement of muscles. Terms preferred for parts of the male terminalia are: (1) gonocoxite and gonostylus for the clasping organ; (2) paramere for the sclerotized plates on each side of and joined to the aedeagus; (3) sternum 10 for paraprocts. Sternum 10 is used because the occurrence of true paraprocts in the Nematocera is questionable. Thirty-four muscles are illustrated, and the origin and insertion of each is described. Eighteen of the muscles are newly described for the mosquito. The rotational muscles of the male terminalia were identified. The results are presented in 21 text figures.     

Homonomies within the ventral muscle system and the associated motoneurons in the locust,Schistocerca gregaria (Insecta,Caelifera)

To understand the segmental reiteration of an insect, the serially arranged neuromuscular system of the locust, Schistocerca gregaria, is studied. The ventral muscle system is chosen and its motoneuronal supply is described in the thoracic and pregenital segments. In general, repetitively arranged, similar sets of motoneurons (MNs) supply the ventral muscles of these segments. Common criteria of both topology of muscles and neural features (nerve branches and motoneuronal supply) suggest possible homonomies of the ventral longitudinal muscles and ventral diaphragm of the thoracic and abdominal system. Based on a segment-by-segment analysis, muscle topology and motor supply match, in most instances. There are, however, cases where such a parallelism is missing. In a particular cases the supply of apparently homonomous muscles shifts from one set of MNs to another. In another case, putatively equivalent MNs of different ganglia supply morphologically different muscle structures in the adult animal. Therefore, it becomes apparent that muscles and their supplying MNs are, in principle, independent elements which might be subjected autonomously to ontogenetic processes. As a consequence, in the search for the basic segmental Bauplan depending on homonomous structures, muscles and MNs have to be regarded as separate entities.Abbreviations A1–6 abdominal ganglion (or neuromere A1–3) - AS1–6 abdominal segment 1–6 - DUM doisal unpaired median - M muscle (number) - MN motoneuron - N nerve (number) - PMN paramedian nerve - T1–3 pro-, meso-, metathoracic ganglion - TS1–3 pro-, meso-, metathoracic segment - VD ventral diaphragm - VM ventral muscle     

The pregenital abdomen of Enicocephalomorpha and morphological evidence for different modes of communication at the dawn of heteropteran evolution

The internal and external anatomy of the posterior metathoracic region, pregenital abdomen, and associated nervous system of the heteropteran infraorder Enicocephalomorpha are thoroughly described, using an array of state-of-the art techniques. Based on morphology, it is hypothesised which modes of communication these insects use. This study is based primarily on an undescribed species of Cocles Bergroth, 1905 (Enicocephalidae) and another undescribed species of Lomagostus Villiers, 1958 (Aenictopecheidae), but additional representatives of the infraorder are also examined. Our results are compared with the literature on other Heteroptera. The metathoracic scent gland system of Enicocephalomorpha uses the same muscles as that of more derived Heteroptera, although the efferent system is different. The presence of a tergal plate and well-developed longitudinal musculature in the families Enicocephalidae and Aenictopecheidae, as well as a sexually dimorphic set of sclerites and membranes that allow an as yet undetermined type of motion, may indicate the presence of vibrational signaling in the infraorder, although experimental confirmation is required. Our findings raise new research questions regarding heteropteran functional morphology and communication.     

On the utility of female genitalia in the systematics of Curculionidae: examples from Entimini and Hylobiina (Coleoptera: Curculionidae)

The utility of the female genitalia and associated sclerites (tergite and sternite VIII) in the systematics of the Curculionidae is discussed. Examples from the tribe Entimini (Entiminae) and subtribe Hylobiina (Molytinae: Hylobiini) are given. The female characters prove to be informative for establishing the phylogenetic relationships among genera of Entimini. They are essential in determining species groups within the genus Arniticus Pascoe, Hylobiina.     

Fine structure of a sensory organ in the arista of Drosophila melanogaster and some other dipterans

Summary The arista, a characteristic appendage of dipteran antennae, consists of 2 short segments at the base and a long distal shaft. A small sensory ganglion, from which arises the aristal nerve, is located proximally in the shaft. The fine structure of the aristal sensory organ was studied in detail in the fruitfly (Drosophila) and for comparison in the housefly (Musca) and the blowfly (Calliphora). In Drosophila, the aristal sense organ consists of 3 identical sensilla that terminate in the hemolymph space of the aristal shaft, and not in an external cuticular apparatus. Each sensillum comprises 2 bipolar neurons and 2 sheath cells; a third sheath cell envelops the somata of all six neurons of the ganglion. The neurons have long slender dendrites with the usual subdivision into an inner and an outer segment. One of the outer segments is highly lamellated and bears small particles (BOSS-structures) on the outside of its cell membrane; the other outer segment is unbranched and has a small diameter. The fine structure of the first dendrite is strongly reminiscent of thermoreceptors known from the antennae of other insects. These thermoreceptors are often coupled with hygroreceptors; however, we can only speculate whether the second dendrite of the aristal organ also has this function. Our present results argue against mechanoreceptive functions, as formerly postulated. The aristal sense organs in Musca and Calliphora are similar to those in Drosophila, but contain more sensilla (12 in Musca, 18 in Calliphora).     

Skeletomuscular development of genital segments in the dragonfly Anax imperator (Odonata, Aeshnidae) during metamorphosis and its implications for the evolutionary morphology of the insect ovipositor

The skeleton-muscular organisation of abdominal segments 7-9 in female Anax imperator L. (Anisoptera, Aeshnidae) was examined in the stages of ultimate larva, teneral imago, and mature imago, with special emphasis on the transformation of the muscle arrangement. The absence of certain muscles in the genital segments compared to the 7th pre-genital segment was noted on all studied stages. Reductions of certain muscles in adults compared to those in larvae are reported. Some of ovipositor's muscles appear already in larvae. Attachment sites of larval muscles are retained in freshly emerged females concurrently with integument transformations. This situation allows for precise determination of the borders of newly differentiated genital sclerites and, therefore, of the possible origin of certain ovipositor elements in odonates. All changes in the segmental sets of studied abdominal muscles during metamorphosis are tabulated, and displacements of muscles are documented and illustrated. Schematic figures illustrating homologies between the parts of larval and imaginal abdominal sclerites are provided. The origins of the components of the endophytic ovipositor in Odonata as well as their implications for the evolutionary morphology of the insect ovipositor are discussed.     

The fate of specific motoneurons and sensory neurons of the pregenital abdominal segments inTenebrio molitor (Insecta : Coleoptera) during metamorphosis

The anatomy and innervation of the lateral external muscle and sensory cells located in the ventral region of pregenital abdominal segments were examined at the larval and adult stages ofTenebrio molitor (Coleoptera). All seven muscles located in this region degenerate during the pupal stage, whilst only the lateral external median (lem) appears in the adult. Backfillings of the motor nerve innervating this muscle reveal that, at both larval and adult stages, it is innervated by ten neurons. Intracellular records from the muscle fibres show that two neurons are inhibitory, and at least five are excitatory. There are also two unpaired neurons. A variety of sensory organs are located in the ventral region of the larvae, whilst only campaniform sensilla are found in the adult. At both stages, the innervation pattern of the sensory nerve branches is very similar. Also, the central projections of the sensory cells occupy similar neuropilar areas. Finally, prolonged intracellular records from the lem muscle revealed that, at the larval stage, it participates only in segmental or intersegmental reflexes, whilst in the adult it has a primary expiratory role in ventilation. The results show that extensive changes occur in the number of muscles located in the ventral region of the pregenital abdominal segments, as well as in the arrangement and number of sensory neurons, in the structure of the exoskeleton, and even in the central nervous system. In contrast, only minor changes are observed in the sensory and motor nerve branches, in the sensory projections, and in the number and the location of the motoneurons innervating the lateral external median muscle. Correspondence to: G. Theophilidis     

XENOCHIRONOMUS TUBEROSUS SP. NOV. FROM SOUTHERN CHINA,WITH EMENDATION TO THE DIAGNOSIS OF THE GENUS (DIPTERA: CHIRONOMIDAE)*

Abstract Xenochironomus tuberosus sp. nov. from southern China is here described and illustrated as male imagines. The new species is separated from other known species of this genus in having frontal tubercle, unusual stout setae on tergite VI, characteristic chaetotaxy on tergite IX and unique superior volsela. Based on the new species, an emendation to the diagnosis of the genus is given. This paper is the first record of genus Xenochironomus from China.     

A possible evolutionary pathway to insect flight starting from lepismatid organization

Starting from the hypothesis that flight in Pterygota evolved from lepismatid organization of their ancestors, the functional anatomy of the thorax was studied in Lepisma saccharina Linnaeus, 1758, and a Ctenolepisma sp. in regard to both the adaptations to the adaptive zone of Lepismatidae and to pre‐adaptations for the evolution of Pterygota. Well‐preserved parts of three subcoxal leg segments were found in the pleural zone participating in leg movement. The lepismatid strategy of escaping predators by running fast and hiding in narrow flat retreats led to a dorso‐ventrally flattened body which enabled gliding effects when dropped, followed by flight on the ground. The presumed exploitation of soft tissue at the tips of low growing Devonian vascular plants opened a canalized pathway to the evolution of the flying ability. Locomotion to another plant was facilitated by dropping. It is possible that threat by spider‐like predators favoured falling and gliding as escape reactions by selection. Falling experiments with `lepismatid' models revealed a narrow `window' for gliding, with optimum dimensions of 8 mm body length and 8 mg weight. An equation was derived which describes the glide distance as function of weight, area of the horizontal outline, the specific glide efficiency of the body, and a non‐linear function of the falling height. Improved gliding was made possible by enlarging thoracic paratergites into broad wing‐like extensions of light‐weight organization. The disadvantage of the lateral lobes for locomotion on the ground could be minimized by tilting them vertically when running and horizontally when gliding. This movability could be attained by the intercalation of a membranous strip between tergite and paratergite and the utilization of the pre‐existing muscular system and the articulation between the two most basal subcoxal sclerites as a pivot. The dorsal part of the most basal subcoxa was thus integrated into the wing. Initiation of active flight was possible by flapping movements during gliding. Morphological, ontogenetic and ecological aspects of the origin of Pterygota are discussed.     

A new octocoral genus (Cnidaria: Anthozoa) from Antarctic waters

Sphaeralcyon weddellensis gen. nov. et sp. nov. is described and illustrated from three colonies collected in the eastern Weddell Sea on the Polarstern cruises ANT V/3 and ANT VI/3. The new genus is compared with three closely related alcyoniid genera, all having capitate or mushroom-shaped colonies and dimorphic polyps. Sphaeralcyon is readily distinguishable from Malacacanthus by the presence of sclerites (absent in the latter genus), and from Anthomastus by sclerite shape, mainly in the form of tuberculate spheroids, and by the horny periderm on the stalk (absent in Anthomastus). Sphaeralcyon also differs from Verseveldtia in the set of sclerites, which are elongate spiny rods and a different type of tuberculate spheroid, and in the presence of eight-points as anthocodial armature (absent in Verseveldtia). The discovery of this new genus lends further support to the notion that diversity in benthic communities in Antarctica is higher than suggested by previous studies. Accepted: 6 December 1999     

The female postabdomen and genitalia of the basal moth family Heterobathmiidae (Insecta: Lepidoptera): Structure and phylogenetic significance

Female Heterobathmia have the segments behind VIII forming a compact ‘terminal unit’ with a large saddle-shaped dorsal plate and a membranous ventroposterior surface bearing the separate gonopore and anus. While females of most of the nine known species are overall similar, Heterobathmia valvifer is unique amongst lepidopterans in possessing paired ventral appendages (‘ovipositor valves’) arising from the intersegmental groove following segment VIII; evidence from musculature contradicts an interpretation of these appendages structures as ‘true’ ovipositor valves. The ventroposterior wall of the terminal unit in H. valvifer bears paired sclerites, possible homologues of the ‘ventral rods’ in basal Lepidoptera-Glossata. In Heterobathmia megadecella sclerites on paired longitudinal elevations in comparable positions probably are/include homologues of these sclerites. Their similarity with paired sclerotizations in the corresponding region of hydrobiosid caddisflies is noted. A prominent frame-like sclerotization in the genital chamber, located in front of the spermathecal duct origin, is present only in H. megadecella.Putative heterobathmiid autapomorphies include an enlarged ‘subgenital plate’ on venter VIII, absence of apophyses on segment VIII, shortened apophyses on the terminal unit, multilobed accessory glands (but their ‘type 1’ secretory epithelium is plesiomorphic at this level), a conspicuous papilla in the chamber cuticle bearing the opening of the ductus bursae on its apex, and inwards-pointing spines in the ductus bursae. A variably developed thickening of the anterior genital chamber intima is another putative family autapomorphy, while an extreme thickening of the posterior intima seen in Heterobathmia pseuderiocrania is not of general occurrence in heterobathmiids. A sistergroup relationship between Heterobathmiidae and Glossata is supported by their fully developed ‘2-compartment section’ of the spermathecal duct and losses of some likely lepidopteran groundplan muscles.