Comparison of Postembryonic Organization of the Genital Segments in Trichoceridae, Tipulidae, and Anisopodidae (Diptera, Nematocera)

The number of abdominal segments in Tipulomorpha and Bibionomorpha larvae and aduts is discussed. For Nematocera, the most primitive number of abdominal segments in both male and female larvae is nine. Reduction of the IX abdominal segment and its subsequent fusion with the VIII segment occurs in different phyletic lines in Nematocera and might have evolved several times. In Trichocera spp. nine abdominal segments are present. In the genital segments the main interrelationships in the position of the anus and some main innervation areas, especially the ventral lobes, and the derivatives of the genital primordia were followed during postembryonic reorganization by studying variously stained serial sections from all developmental stages from the first larval instar to the adult stage. Homologies between male and female derivatives of the IX segment genital primordium were established for Trichoceridae. The trichoceroid male claspers and female ovipositor were found to be of sternal origin and highly specialized structures. They appear to be unique features of the Tipulomorpha. Postembryonic development in Limonia nubeculosa Meigen, 1804 and Sylvicola cinctu (Fab-ricius, 1787) was studied in the same way. In Limonia males the trichoceroid functional system for grasping is present. In Anisopodidae ( Sylvicola ), another functional system for grasping has been evolved by the male, which only includes primordial derivatives. In the adults, fusion of the VIII and IX segments prevents development of outer clasping organs or special structures for egg guidance.     

Musculature of the ovipositor of <Emphasis Type="Italic">Oxyna parietina</Emphasis> (Linnaeus, 1758) (Diptera,Tephritidae) and its relation to the larval habits

The structure of the ovipositor sclerites and muscles was studied in the tephritid fly Oxyna parietina (Linnaeus, 1758) inducing galls on the stems of Artemisia vulgaris. Adaptations of the ovipositor structure associated with changes of the oviposition substrate due to new larval habits are analyzed. The ovipositor muscles of Oxyna parietina are compared to those of Campiglossa. The genera Oxyna Robineau-Desvoidy, 1830 and Campiglossa Rondani, 1870 belong to the same genus-group of Tephritini, but differ in their host associations and oviposition habits: the larvae of Campiglossa plantaginis (Haliday, 1833) develop in the capitula of Aster tripolium and other asters (Asteraceae). The ovipositor sclerites and muscles are similar in the two genera. Progression of hemolymph into the membranous sheath of the ovipositor and protraction of the aculeus are necessary conditions for laying eggs into the capitula of Asteraceae (Campiglossa plantaginis), as well as for insertion of eggs into the axils of Artemisia leaves (Oxyna parietina). The most significant characters of Oxyna and Campiglossa include the presence of the hyaline apodeme and associated muscles MVM 6 and MVM 7 (instead of the median apodeme in Urophora). Thus, in other tephritid flies similarity in the structure of the ovipositor muscles may reflect similar morphofunctional adaptations to laying eggs into similar substrates, but similarity of Campiglossa and Oxyna in the structure of the ovipositor muscles is due to their close relations.     

Comparative anatomy of muscle sets in larval and adult stages ofZophobas morio (Coleoptera,Tenebrionidae)

Summary The muscles of the metathoracic segment are described for the larva and imago of the beetleZophobas morio. In the search for possible homonomous and ontogenetic persistent structures, we further employed muscles served by the first segmental nerve in the thoracic and abdominal segments. In the larva, eight muscles per hemisegment are associated with this nerve. Based on topological criteria they may be characterized as homonomous for all tested segments. In the adult, the topology of the dorsal muscles seems to be different compared to the larval situation, due to the complex structural remodelling during metamorphosis. However, a supplementary analysis employing the innervation pattern allows us to equate larval with adult muscles, even down to the level of individual motor units. Comparison of different orthopteran and coleopteran species provides some evidence that these muscles are homologous, apparently representing part of a basic pattern common in pterygote insects.     

Musculature of the ovipositor of Lenitovena trigona (Matsumura) (Diptera, Tephritidae) with reference to the larval saprophagy

The larvae of most Tephritidae are endobiotic in various living plants and are therefore convenient objects for analysis of the associations of this dipteran family with seed plants. The structure of the sclerites and musculature of the ovipositor of Lenitovena trigona (Matsumura) a Far Eastern tephritid of the tribe Acanthonevrini with initially saprobiont larva, was investigated to facilitate understanding of the morphological changes in the adults associated with larval shift from saprophagous to herbivorous habit. Differences between the ovipositor of L. trigona and those of species of the genera Urophora, Ceratitis, and Rhagoletis with endophytic larvae have been found; the ovipositor musculature of these genera has been described by Dean (1935), Nanna (1938), and Berube and Zacharuk (1983).     

The morphology and evolution of the female postabdomen of Holometabola (Insecta)

In the present article homology issues, character evolution and phylogenetic implications related to the female postabdomen of the holometabolan insects are discussed, based on an earlier analysis of a comprehensive morphological data set. Hymenoptera, the sistergroup of the remaining Holometabola, are the only group where the females have retained a fully developed primary ovipositor of the lepismatid type. There are no characters of the female abdomen supporting a clade Coleopterida + Neuropterida. The invagination of the terminal segments is an autapomorphy of Coleoptera. The ovipositor is substantially modified in Raphidioptera and distinctly reduced in Megaloptera and Neuroptera. The entire female abdomen is extremely simplified in Strepsiptera. The postabdomen is tapering posteriorly in Mecopterida and retractile in a telescopic manner (oviscapt). The paired ventral sclerites of segments VIII and IX are preserved, but valvifers and valvulae are not distinguishable. In Amphiesmenoptera sclerotizations derived from the ventral appendages VIII are fused ventromedially, forming a solid plate, and the appendages IX are reduced. The terminal segments are fused and form a terminal unit which bears the genital opening subapically. The presence of two pairs of apophyses and the related protraction of the terminal unit by muscle force are additional autapomorphies, as is the fusion of the rectum with the posterior part of the genital chamber (cloaca). Antliophora are supported by the presence of a transverse muscle between the ventral sclerites of segment VIII. Secondary egg laying tubes have evolved independently within Boreidae (absent in Caurinus) and in Tipulomorpha. The loss of two muscle associated with the genital chamber are likely autapomorphies of Diptera. The secondary loss of the telescopic retractability of the postabdomen is one of many autapomorphies of Siphonaptera.     

Homeotic gene function in the muscles of Drosophila larvae

The segmental musculature of Drosophila melanogaster larvae consists of 24-30 muscles per segment. Unique patterns of muscles are found in the three thoracic segments and the first and last abdominal segments; the remaining abdominal segments share the same pattern. Mutations in Ultrabithorax (Ubx) cause partial transformation of the muscle pattern of larval abdominal segments towards metathorax. The muscles of the thorax are not affected. In the first two abdominal segments the changes include the loss of at least 11 `abdominal' muscles and the gain of 11 `thoracic' muscles. Less extensive transformations are seen in more posterior abdominal segments. Anterobithorax, bithorax, postbithorax and bithoraxoid mutations also induce transformations of the larval musculature. Each allelic group affects a domain that is a subset of the entire Ubx domain but these domains are not restricted to compartments or segments and may extend through as many as five segments. In the muscles the segmental distribution of Ubx antigen correlates with the segments affected by Ubx mutations. The different domains of Ubx in mesoderm and ectoderm argue that the segmental diversity of the muscle pattern is not simply induced by the overlying epidermis and that Ubx function in the mesoderm is required for the correct development of abdominal segments.     

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.     

长蝎蛉幼期形态附生物学记述

【目的】蝎蛉科(Panorpidae)是长翅目(Mecoptera)最大的科,是重要的生态指示昆虫。然而,由于对环境条件要求苛刻,饲养困难,其幼期研究很不充分。【方法】本研究通过人工饲养成虫获得了长蝎蛉Panorpa macrostyla Hua的卵、幼虫和蛹等全部虫态,运用光学显微镜和扫描电子显微技术观察了其超微形态,并简要记载了其生物学特性。【结果】长蝎蛉每年发生1代,成虫发生于6月末至8月初。卵椭球形,卵壳表面覆盖一层隆起的网状结构。幼虫蠋型,具3对分4节的胸足和8对不分节的腹足;头壳高度骨化,具1对由26个小眼组成的复眼和1对3节的触角,口器咀嚼式;腹部第1-9节背面具有成对的背毛突,第10节仅有1根背毛突,腹部末端具有一个可伸缩的吸盘;呼吸系统为周气门式,具1对前胸气门和8对腹气门。幼虫共4个龄期,以预蛹期在土室内越冬。蛹为强颚离蛹,外形接近成虫,雄蛹腹部末端膨大。【结论】基于幼虫形态特征,长蝎蛉明显区别于新蝎蛉属Neopanorpa、华蝎蛉属Sinopanorpa、双角蝎蛉属Dicerapanorpa以及单角蝎蛉属Cerapanorpa幼虫。然而,长蝎蛉幼虫头部刚毛L2和SO2,腹部末节刚毛D2,SD1和SD2端部均膨大呈棒状,与蝎蛉属Panorpa其他种类区别明显,表明长蝎蛉的属级地位需要进一步研究。     

Anatomy and innervation of the abdominal segmental muscles in larval and adult Tenebrio molitor (Coleoptera)

The external morphology, musculature, and the innervation of the abdominal segments were examined in larvae and adult Tenebrio molitor. In the larva, there are 26 pairs of muscles arranged at four different levels in the ventral, lateral, and dorsal region of each segment. In the adult, the number of muscles has been dramatically reduced and is limited to six pairs of muscles located at the dorsal and lateral region of the segment. These muscles, in either larval or adult stages, are innervated by two main nerves, n1 and n2, which originate from the segmental ganglia. The cell bodies of the motoneurons innervating the muscles of the 3rd abdominal segment are located in the 3rd and 2nd abdominal ganglia. Some cell bodies are retained throughout metamorphosis, but others disappear during the larva-pupa transition.     

Homology of the genital sclerites of Megaloptera (Insecta: Neuropterida) and their phylogenetic relevance

The genitalia of Megaloptera are crucial for taxonomic identification and represent a significant component of characters for phylogenetic interpretation of this order. However, several complex genital structures, especially those related to segments 9 and 11 in Megaloptera, have yet to be subjected to a comprehensive survey of homology. The terminology for genital sclerites has been variously and even incorrectly used by different authors, a fact which could lead to much confusion about character evolution. In this paper, we first present a comprehensive morphological comparison of the sclerites of male and female genital segments in 23 megalopteran genera representing all major lineages of Corydalinae, Chauliodinae and Sialidae. Accordingly, we then provide new interpretations on the homology of the genital sclerites which often appear to be considerably different among Megaloptera. Based on our new and revised homology assessments, we conclude that: (i) the small to medium‐sized sclerite beneath the ectoprocts in males of Sialidae represents the fused gonocoxites 11; (ii) the male gonocoxites 11 in Corydalidae are largely reduced and are sometimes retained as a small sclerite beneath the anus; (iii) the predominant sternite‐like sclerite of the female abdominal segment 8 represents the fused gonocoxites 8; and (iv) a pair of sclerites amalgamated with the lateral arms of male gonocoxites 10 in Chauliodinae is the gonocoxites 9. Furthermore, based on our genital homology assessments, we reconstruct an intergeneric phylogeny including all genera of Megaloptera using genital characters in a parsimonious analysis to test their phylogenetic relevance. The phylogeny herein recovered is largely congruent with the results from several previous studies, thus underlying the significant phylogenetic relevance of the megalopteran genital sclerites. The present work provides new insights into the evolution of insect genitalia.     

The transstadial and vertical transmission of a granulosis virus from the corn borer Sesamia nonagrioides

The effects of a granulosis virus from Sesamia nonagrioides were established in the larval, pupal, and adult stages. Different ages of larvae were compared as to their survival rates. Pupae deriving from diseased larvae had a sex ratio that deviated from the expected 1:1; in some of these pupae an incomplete pigmentation was noticed in abdominal segments. Adults deriving from inoculated larvae were less fertile, as measured by oviposition and by hatching rate. Offspring of inoculated parents had a greater incidence of the granulosis virus disease than did offspring of uninoculated parents.     

Superextension and supercontraction in locust ovipositor muscles

A ten times elongation of certain abdominal intersegmental muscles occurs in female locusts during digging prior to oviposition. During and after oviposition the muscles contract, shortening by up to 90% or more, restoring the resting positions of the abdominal segments.Discontinuous Z-discs permit supercontraction at the resting length and then fragment into Z-bodies when the muscle is stretched, so enabling it to superextend without loss of the contractile property. In this superextended state the fibres resemble smooth muscles. After oviposition, the muscle fibres contract but the sarcomeres are not restored completely, some of the Z-bodies being unevenly distributed in the recontracted fibres. Locust ovipositor muscle has the most extreme example of Z-disc disagregation known from the insects and is the insect muscle which approaches most closely the smooth muscle condition.Two types of motor nerve innervate this muscle, one is ordinary and the other, containing granules, resembles an octopaminergic fibre possibly involved in regulating a catch mechanism in the muscle.The physiological requirements for egg-laying with an extensible ovipositor, which is also part of the normally functioning abdomen, are well met by the ultrastructural specializations of locust ovipositor muscles.     

The muscular system of the ovipositor of Spaziphora hydromyzina (Fallén) (Diptera, Scathophagidae)

The structure of the ovipositor sclerites and muscles was investigated in Spaziphora hydromyzina (Diptera, Scathophagidae).     

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     

What is the epipleurite? A contribution to the subcoxal theory as applied to the insect abdomen

The epipleurites were originally described by Hopkins in 1909 on the imago and larva of a beetle. Then this term was widely used in insect morphology, mainly for larvae, to designate certain sclerites of the pleural region. They have recently been interpreted as tergopleural (i.e. pleural but not strictly appendicular) by Deuve in 2001, but a study of embryonic development by Kobayashi et al. in 2013 has shown that they are instead eupleural (i.e. appendicular) and correspond to a dorsal part of the subcoxa. Their presence in the abdominal segments of insects illustrates the fundamental importance of the subcoxa in segmental structure, with a function of anchoring and supporting the appendage when the latter is present. However, the epipleurites are normally separated and functionally dissociated from the coxosternum, which integrates the ventral component of the subcoxa. In females, the epipleurite of segment IX of the abdomen corresponds to the gonangulum, as already pointed out by Deuve in 1994 and 2001, and it is involved in gonopod articulation. At segments VIII and IX of both males and females of holometabolans, the formation process of the genital ducts leads to an internalisation of the whole subcoxosternum (i.e. the coxosternum with the exception of the coxal and telopodal territories), and it is the two flanking epipleurites that ventrally close the abdomen in relation to the rearward displacement of the gonopore. This model may be generalised, in its broad lines, to a large part of the hemimetabolans. The body plan of the insect abdomen underlines the morphological and functional importance of the subcoxa in its fundamental structure, but the study of the Hexapoda in general also indicates the presence of a more proximal segment, the precoxa, which would belong to the groundplan but is more cryptic because it is often closely associated with the subcoxa and/or the paranotal lobe. Its location, which is sometimes on the ventral flank of the paranotal lobe, is in line with the hypothesis of a dual origin of the pterygote wing.     

A comparison of techniques used to study the morphology of final instar larvae of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae)

Abstract. The morphology of the head sclerites of final instar larvae of aphid parasitoids prepared from cast larval skins and excised heads of whole larvae are compared, using both optical and scanning electron microscopy. Remarkable differences in the apparent shape of head sclerites, particularly mandibles, were found. Some of these differences are probably due to a consistent dorso-ventral flattening of the head during moulting, observed in cast skin preparations, whereas excised heads tend to flatten antero-posteriorly. The importance of these findings for understanding the three-dimensional shape of final instar mandibles and for the study of larval morphology and taxonomy of Hymenoptera is discussed     

Development of the sensory system in larvae and pupae of Chaoborus crystallinus (DeGeer, 1776; Diptera, Chaoboridae): sensory cells, nerves and ganglia of the tail region

Using various microscopical techniques, we have studied changes in the sensory equipment and architecture of the peripheral nervous system (PNS) around the first metamorphic molt from larva to pupa in the phantom midge Chaoborus. The transparent larvae and pupae of this dipteran with ancestral features allow us to investigate sensilla and their central projections from whole-mount preparations of complete groups of segments. Each sensillum on the posterior larval and pupal segments was identified using its external shape and position, and the morphology of the abdominal ganglia and segmental nerves was investigated. In addition, retrograde fills with the carbocyanine dye DiI were used to trace the axonal paths of most of the extero- and proprioreceptors. These findings were combined to produce maps of the sensory elements of larval and pupal abdomens that were analyzed at three levels: seriality (homonomy), ontogenetic changes of individual sensilla, and homology of the PNS between different species. Comparison of different segments shows for both stages that primarily there is a homonomous basic design of the PNS, but segment-specific modifications are evident in segments 8-10. Comparison of corresponding larval and pupal segments shows that many sensilla retain their internal structure and axonal projections. However, their external cuticular parts are changed in relation to the different life habits of larvae and pupae. Furthermore, some sensilla are completely reduced during the pupal molt, especially those of the tenth segment which appears as a distinct larval structure (caenogenesis). Comparison between species indicates that despite the varying types of sensilla their basic segmental arrangement and their axonal trajectories are conserved.