Anatomy and mechanics of the telescopic ovipositor system of Scelio latreille (Hymenoptera: Scelionidae) and related genera

The telescopic ovipositor system possessed by the genus Scelio Latreille (Hymentoptera : Scelionidae) and related genera is described in detail for the first time, and found to be anatomically and mechanically unique amongst the parasitic Hymenoptera. Its basic plan is similar to the Ceratobaeus-type ovipositor system described previously for other scelionids, in that the ovipositor is invaginated entirely into the body cavity when at rest and attached to the terminal metasomal segment only by a lightly sclerotized collapsible membranous tube. There are, however, significant anatomical and mechanical modifications that permit the Scelio-type system greater extendability. Telescopic extension of multiple sections of greatly elongated intersegmental membrane, operated by changes in hydrostatic pressure, allows the entire ovipositor system, including the terminal metasomal tergite (T7 + T8), to be exserted from the body cavity during oviposition, thus extending the range of the ovipositor by as much as 3.5 times its length. These changes are accompanied by the incoporation of the lateral apodemes into the wall of the most distal segment of telescopic tube, and the loss of their associated musculature. Similar to other scelionids, orientation of the ovipositor in Scelio is controlled by contraction of muscles connecting the proximal head of the ovipositor with the fused terminal metasomal tergite (T7 + T8). A model for the mechanics of extension and retraction of the Scelio-type ovipositor system is proposed, and is supported by anatomical evidence, behavioural observations and direct manipulation of the system. The evolution of this system in relation to the exploitation of a particular host group, the eggs of Orthoptera, and its significance in resolving phylogenetic problems within the Scelionidae, are also discussed.     

Phylogeny of the platygastroid wasps (Hymenoptera) based on sequences from the 18S rRNA, 28S rRNA and cytochrome oxidase I genes: implications for the evolution of the ovipositor system and host relationships

The Platygastroidea are a diverse group of mostly small to tiny wasps, the common biology for which is endoparasitism of insect and spider eggs. No analytically‐based phylogeny exists for the superfamily, and the current suprageneric classification is flawed in part because of its reliance on homoplasious and pleisiomorphic morphological characters. To determine platygastroid relationships as a basis for investigating host and ovipositor evolution, phylogenies of > 70 in‐group species (representing 55 genera) were reconstructed by parsimony and Bayesian methods using three molecular markers; the mitochondrial cytochrome oxidase I and the nuclear genes 28S and 18S rRNA. The results strongly support the monophyly of the superfamily and one of the two families, Platygastridae, but the Scelionidae are most likely polyphyletic. However, within the Scelionidae, there is a well supported ‘main scelionid clade’ that contains the majority of genera assigned to the family. At the subfamilial level, both putative subfamilies of Platygastridae, the Platygastrinae, and Sceliotrachelinae, are likely to be polyphyletic. Within the Scelionidae, both the Teleasinae and Telenominae are monophyletic, but the Scelioninae is clearly not so. The current tribal classification for the Scelionidae is in need of major reassessment because no tribes, with the exception of the Scelionini s.s., were found to be monophyletic. Further illustrating the problems associated with the current classification is the nonmonophyly of a number of genera, namely Opisthacantha Caloteleia, Telenomus, Trimorus, Teleas and Idris. Analysis of ovipositor evolution in the superfamily revealed that the Ceratobaeus‐type ovipositor system is ancestral; however, this trait was lost prior to the evolution of the main scelionid clade, for which the Scelio‐type ovipositor system is ancestral and defines a mostly paraphyletic assemblage. Ancestral state analysis indicates that the Ceratobaeus‐type ovipositor was subsequently re‐evolved in the main scelionid clade, representing a possible contradiction of Dollo’s law. Previously, the tribal placement has been used to predict the host associations of genera for which host data were unavailable. However, the fact that most tribes are not monophyletic throws into doubt any such speculation based on the current classification. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91 , 653–669.     

Spider silk felting—functional morphology of the ovipositor tip of Clistopyga sp. (Ichneumonidae) reveals a novel use of the hymenopteran ovipositor

Apical serrations of the hymenopteran ovipositor have been widely postulated to originally constitute adaptations for cutting through hard substrates. Simplifications of the ovipositor tip have occurred in several ichneumonid wasp genera associated with spiders. Despite such reduction in Clistopyga (Hymenoptera, Ichneumonidae), the ovipositor still possesses some apical serrations. Through the first detailed study, we believe, on the behaviour of an ovipositing Clistopyga species, we show that it can alter its ovipositor for different purposes and that the primary function of the apical serrations is clinging to its spider host as the spider attempts to escape. Intriguingly, we also discover a hitherto undocumented adaptation for the hymenopteran ovipositor. The female wasp seals openings in the silken spider nest by using its ovipositor on the silk in a highly sophisticated way that is comparable to how humans entangle wool by needle felting. By studying the ovipositor morphology through a scanning electron microscope, we elucidate how this works, and we hypothesize that by closing the nest the female wasp protects its developing kin.     

Sense organs on the ovipositor of Macrocentrus cingulum Brischke (Hymenoptera: Braconidae): their probable role in stinging,oviposition and host selection process

Parasitoid wasps from the insect order Hymenoptera can be deployed successfully as biological control agents for a number of pests, and have previously been introduced for the control of corn pest insect species from the Lepidopteran genus Ostrinia. Organs on the ovipositor of parasitoid wasps have mechanical and tactile senses that coordinate the complex movements of egg laying, and the ovipositor of Hymenopteran insects have evolved associated venom glands as part of their stinging defense. The ovipositor of parasitic wasps has evolved an additional function as a piercing organ that is required for the deposition of eggs within suitable host larvae. The morphology and ultrastructure of sense organs on the ovipositor and sheath of Macrocentrus cingulum Brischke (Hymenoptera: Braconidae) are described using scanning and transmission electron microscopy. Three types of sensilla trichodea were shown to be abundant on the outer sheath of the ovipositor, with types II and III being most distal, and the inner surface of the ovipositor covered with microtrichia, more densely near the apex. Sensilla coeloconica are distributed on both ventral and dorsal valves, while campaniform sensilla and secretory pores are only located on the dorsal valve. The olistheter-like interlocking mechanism, as well as the morphology of the ventral and dorsal valve tips and the ventral valve seal may be important in stinging, oviposition and in the host selection process.     

Functional anatomy of the ovipositor clip in the parasitoid leptopilina heterotoma (Thompson) (Hymenoptera : Eucoilidae), a structure to grip escaping host larvae

Observations on the host attack behaviour of the parasitoid Leptopilina heterotoma (Hymenoptera : Eucoilidae) led to the supposition that this wasp should possess a structure on its ovipositor by which it can hold a host larvae in a fixed position until the larva is paralyzed. The ovipositor was studied by light, scanning and transmission electron microscopy and appeared to have a clip with teeth on the unpaired valve of the ovipositor, about 50 μm from the tip. Based on the structure of this ovipositor clip and the oviposition behaviour, the functioning of the ovipositor clip is discussed.     

The ovipositor musculature of Carpomya schineri (Loew) (Diptera, Tephritidae)

The structure of the ovipositor sclerites and musculature was studied in the tephritid fly Carpomya schineri (Loew) whose larvae develop in the fruits of Rosa. The structural characters of the ovipositor of this species facilitating laying eggs into such fruits are discussed. The ovipositor musculature and functioning in Carpomya are very similar to those in Ceratitis and Bactrocera; species of all these genera lay eggs in fruits. In the details of the ovipositor musculature, Carpomya is more similar to Ceratitis than to Bactrocera. The genera Carpomya, Ceratitis and Bactrocera are phylogenetically close but Ceratitis and Bactrocera belong to sister tribes within one subfamily, Dacinae. Thus, morpho-functional similarity of the ovipositor structure may not only reflect close relationship but also result from common adaptive transformations.     

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).     

Review of <Emphasis Type="Italic">Dotocryptus</Emphasis> Brèthes (Hymenoptera,Ichneumonidae, Cryptinae), with a New Species from Colombia

The taxonomic limits of the Neotropical genus Dotocryptus Brèthes are reviewed. The genus is characterized mainly by the very long ovipositor, at least 2.2× as long as hind tibia; apex of ovipositor distinctly depressed, ventral valve expanded, and overlapping dorsal valve as a sheath; and mandible long with ventral tooth longer than dorsal one. A new species, Dotocryptus arcadius sp. nov., from Colombia is described and illustrated. The new species can be diagnosed mainly by the head and mesosoma with multiple whitish marks; epicnemial carina reaching 0.2–0.3 of distance to subalar ridge; legs marked with dark brown, orange, and whitish; and metasoma polished and glabrate. This is the northernmost record of the genus, previously known from Ecuador to southern Chile. An updated identification key to the species of the genus is provided, as well as diagnoses and new records for the previously known species.     

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.     

Assessing the morphological and physiological adaptations of the parasitoid wasp Echthrodesis lamorali for survival in an intertidal environment

As a result of a variety of chemical, environmental, mechanical and physiological difficulties, insects that spend their entire life spans in the marine or intertidal region are relatively rare. The present study assesses whether morphological and physiological adaptations have evolved in a maritime parasitoid wasp species Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae, Scelioninae), in response to environmental pressures on its respiratory functioning. Scanning electron and light microscopy of whole and sectioned specimens show the presence of structure‐retaining taenidia in the tracheal tubes, although there is an absence of other major adaptations associated with the trachea or spiracles. Histological sectioning reveals the presence of unusual sacs in the female metasoma whose role is unknown, although they are hypothesized to most likely be linked to ovipositor control. Respirometry experiments illustrate the formation of a plastron when submerged, with the longevity of the wasps being increased by quiescence. The critical thermal range of E. lamorali is shown to be large: from ?1.1 °C ± 0.16 to 45.7 °C ± 0.26 (mean ± SE). Behavioural and physiological adaptations in E. lamorali appear to have evolved in response to exposure to the heterogeneous environmental conditions experienced within the intertidal zone.     

Revision of the tribe Colpopterini Gnezdilov, 2003 (Homoptera, Fulgoroidea: Nogodinidae)

The tribe Colpopterini Gnezdilov, 2003 is revised, upgraded to the subfamily Colpopterinae, stat. n., and transferred from the family Issidae Spinola to Nogodinidae Melichar. The tribe Colpopterini is recorded from the Afrotropical Region for the first time—Bumerangum deckerti gen. et sp. n. is described from Southern Africa. The tribe Colpopterini s. str. comprises 6 genera: Bumerangum gen. n., Caudibeccus Gnezdilov et O’Brien, 2008, Colpoptera Burmeister, 1835, Jamaha Gnezdilov et O’Brien, 2008, Neocolpoptera Dozier, 1931, and Ugoa Fennah, 1945. The genera Cheiloceps Uhler, 1895, Tempsa Stål, 1866, Eupilis Walker, 1857, and Gabaloeca Walker, 1870 are transferred to the tribe Issini Spinola of the family Issidae. Issus longulus Lethierry, 1890 is transferred to the genus Colpoptera Burmeister. A key to the genera and a list of the species of the tribe Colpopterini are given. Morphological data confirming independent evolution of similar ovipositor types in the families Issidae and Nogodinidae are provided. The term “styletization” is suggested for describing the transformation of the ovipositor from a rounded to an elongate type.     

A new species of the genus Himertosoma from the Ryukyus,Japan, with a key to species from the Palaearctic and Oriental Regions (Hymenoptera,?Ichneumonidae,Banchinae)

A new species of the genus Himertosoma Schmiedeknecht, Himertosoma kuslitzkii sp. n., was discovered in Amamioshima Island, the Ryukyus. This new species resembles two Oriental species, Himertosoma philippense Chandra & Gupta and Himertosoma townesi Chandra & Gupta, in the colour pattern of the head and metasoma, number of flagellomeres, and the relatively slender first metasomal tergite, but can easily be distinguished from them by the nearly evenly punctate propodeum, different length/width ratio of the first metasomal tergite, different length of the ovipositor sheath, tricoloured mesosoma, and the whitish band along the posterior margin of the second and following metasomal tergites. A key to the Palaearctic and Oriental species of Himertosoma is also provided.     

The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism,Sexual Body Component Dimorphism,and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

Sexual differences in morphology, ranging from subtle to extravagant, occur commonly in many animal species. These differences can encompass overall body size (sexual size dimorphism, SSD) or the size and/or shape of specific body parts (sexual body component dimorphism, SBCD). Interacting forces of natural and sexual selection shape much of the expression of dimorphism we see, though non-adaptive processes may be involved. Differential scaling of individual features can result when selection favors either exaggerated (positive allometry) or reduced (negative allometry) size during growth. Studies of sexual dimorphism and character scaling rely on multivariate models that ideally use an unbiased reference character as an overall measure of body size. We explored several candidate reference characters in a cryptically dimorphic taxon, Hadrurus arizonensis. In this scorpion, essentially every body component among the 16 we examined could be interpreted as dimorphic, but identification of SSD and SBCD depended on which character was used as the reference (prosoma length, prosoma area, total length, principal component 1, or metasoma segment 1 width). Of these characters, discriminant function analysis suggested that metasoma segment 1 width was the most appropriate. The pattern of dimorphism in H. arizonensis mirrored that seen in other more obviously dimorphic scorpions, with static allometry trending towards isometry in most characters. Our findings are consistent with the conclusions of others that fecundity selection likely favors a larger prosoma in female scorpions, whereas sexual selection may favor other body parts being larger in males, especially the metasoma, pectines, and possibly the chela. For this scorpion and probably most other organisms, the choice of reference character profoundly affects interpretations of SSD, SBCD, and allometry. Thus, researchers need to broaden their consideration of an appropriate reference and exercise caution in interpreting findings. We highly recommend use of discriminant function analysis to identify the least-biased reference character.     

Antennal and ovipositor sensilla of Pseudoligosita yasumatsui (Hymenoptera: Trichogrammatidae)

Pseudoligosita yasumatsui Viggiani and Subba Rao 1978 (Hymenoptera: Trichogrammatidae) is a common egg parasitoid of rice insect pests. The surface morphology of the antenna and ovipositor on P. yasumatsui was examined using scanning electron microscopy. The antenna of P. yasumatsui is geniculate in shape, hinged at the scape-pedicel joint, approximately 190 μm in length and consists of seven antennomeres. In total, the male and female antennae have ten different types of sensilla: trichoid sensilla type 1, 2, 3, 4, 5, 6, campaniform sensilla, basiconic sensilla, and placoid sensilla type 1 and 2. The flagellum of the female antenna is covered with cuticular pores, which are absent on the male antennal flagellum. The distal extremity of its ovipositor stylet has campaniform sensilla and styloconic sensilla. Trichoid sensilla found on its apical abdomen part may play a role in the host detection and egg placement. The types and distribution of antennal and ovipositor sensilla on the parasitoid were discussed.     

Sexual dimorphism of antennal and ovipositor sensilla of Tetrastichus sp. (Hymenoptera: Eulophidae)

Tetrastichus sp. (Hymenoptera: Eulophidae) is a primary parasitoid of the Metisa plana (Lepidoptera: Psychidae), an oil palm bagworm. The sensilla on the surface of the antenna and ovipositor of Tetrastichus sp. were examined using a scanning electron microscope. The antennae of both male and female Tetrastichus sp. are geniculate in shape and hinged at the scape-pedicel joint. The female antenna is about 200 µm longer than the male antenna. However, the male antenna has an additional flagellomere compared to the female antenna. In total, eight different types of antennal sensilla were observed on the antenna of Tetrastichus sp.: trichoid sensilla type 1, 2, 3, 4, placoid sensilla type 1 and 2, basiconic sensilla, and campaniform sensilla. The antenna of the female Tetrastichus sp. lacks placoid sensilla type 2 and campaniform sensilla. The distribution and abundance of the antennal sensilla were compared between the male and female Tetrastichus sp. and discussed. On the ovipositor stylet of Tetrastichus sp., coeloconic sensilla, styloconic sensilla and campaniform sensilla were observed. Trichoid sensilla were observed at the medial part of the distal extremity of the ovipositor.     

A new species of Parapanteles Ashmead, 1900 (Hymenoptera: Braconidae: Microgastrinae) parasitic on Charaxes athamas (Drury) (Lepidoptera: Nymphalidae) in India

A new species of gregarious endoparasitoid, Parapanteles athamasae n. sp. (Hymenoptera: Braconidae), parasitising caterpillars of Charaxes athamas (Drury) (Lepidoptera: Nymphalidae) on the host plant Senegalia catechu (=Acacia catechu) (L.f.) Hurter & Mabb., is described from Maharashtra, India. Diagnostic characters of the new species include: propodeum with areola 0.93× longer than wide, legs yellow, hind tibia 4.30× as long as ovipositor, ovipositor sheaths exerted, first metasomal tergal plate 1.24× longer than wide, with coarse sculpture merging with longitudinal striations at 3/4 of the apical region. This is the first time a species of the family Nymphalidae Rafinesque is recorded in association with Parapanteles Ashmead, 1900. A key to the Indian species of Parapanteles based on females is also provided.     

A new species of <Emphasis Type="Italic">Uniclypea</Emphasis> Bouček, 1976 (Hymenoptera: Pteromalidae) parasitic on <Emphasis Type="Italic">Apoderus tranquebaricus</Emphasis> Fabricius (Coleoptera: Attelabidae) from India with notes on biology

One new species of parasitic wasp, Uniclypea similis n. sp. (Hymenoptera: Pteromalidae), reared from the leaf knots constructed by Apoderus tranquebaricus Fabricius (Coleoptera: Attelabidae) on the host plant Grewia abutilifolia Vent. ex Juss. is described and illustrated. The characteristic features of the new species are: post-marginal vein 2.3× stigmal vein, metasoma length 4.3× its width and costal cell 1.47× marginal vein. To my knowledge, the male of a species of Uniclypea is described and illustrated for the first time.     

Meek mothers with powerful daughters: effects of novel host environments and small trait differences on parasitoid competition

Outcomes of competition may depend both on subtle differences in traits relevant to fitness and on how those traits are expressed in the context of the environment. Environmental effects on traits impacting population dynamics are often overlooked in studies of parasitic wasp (parasitoid) competition. Lineages of the parasitoid Diachasma alloeum (Hymenoptera: Braconidae) differ in relative ovipositor length (a trait affecting the proportion of hosts available for parasitism). Since the size of natal hosts affects the overall body size of many adult parasitoids, outcomes of competition between D. alloeum lineages should be influenced by both their natal host's size and their inherited ovipositor:body size ratios. Previous genetic work showed the unexpected result that the apparently inferior competitor (the lineage with smaller ovipositors in its ancestral environment) has successfully colonized a new host. We present body size measurements and a phenomological model of competition showing that relative ovipositor sizes of the two lineages predict success of the apparently inferior wasp lineage in the new host. We present several variants of the model, including simulations: 1) wherein competitors have either ancestral trait values or trait values acquired in the novel environment; 2) that allow varying rates of constant immigration from the inferior competitor's source population; and 3) with stochastic immigration from both lineages' source populations. We show that ancestral trait differences and changes in environmentally mediated traits interact to affect outcomes of competition. Apparently inferior female parasitoids (‘meek mothers’) attacking a host in a novel environment can produce highly successful daughters if those daughters inherit large ovipositor:body size ratios and grow to a larger size in the new environment. Predictive models of parasitoid competition that consider effects of environmentally mediated trait changes may be particularly important for biocontrol programs wherein parasitoids are introduced into new environments or used to control novel hosts.     

A review of the genera <Emphasis Type="Italic">Calotelea,Calliscelio</Emphasis>, and <Emphasis Type="Italic">Oxyscelio</Emphasis> (Scelioninae,Scelionidae, Proctotrupoidea) from the Palaearctic fauna

Nine new species of scelionids collected in Japan, Israel, and the Ukraine, Calotelea shimurai Kononova et Fursov, C. japonica Kononova, C. stellae Kononova, Calliscelio recens Kononova, C. floridum Kononova, C. parilis Kononova, C. ordo Kononova, Oxyscelio florum Kononova, and O. perpensum Kononova, are described. A brief morphological characteristics of the mentioned genera and some data on the geographical distribution of these species are given. Calotelea shimurai differs from C. striola Kononova in the sculpture of the metasoma (tergites I–III striate, whereas in C. striola striation present only on tergites I and II), fore-wing venation (stigmal vein of C. shimurai 0.43 times as long as postmarginal vein and 1.75 times as long as marginal one; in C. striola, stigmal vein 0.52 times as long as postmarginal vein and 1.3 times as long as marginal one), and the length of the metasoma (in C. shimurai and C. striola, metasoma 4.0 and 2.3 times as long as wide, respectively). Calotelea shimurai parasitizes in eggs of the dragonflies Aeshna nigroflava Martin, Planaeschna milnei Selys, and Boyeria macachlani (Aeshnidae, Odonata). C. japonica is closely related to C. originalis Kozlov and Kononova, but differs from it in the sculpture of the metasoma (metasomal tergites with longitudinal wrinkles against the bright smooth background; in C. originalis, tergites I and II with longitudinal wrinkles against the alveolate background), in the coloration of fore wing (infuscate in C. japonica and dark, with dark transverse stripes in C. originalis). C. stellae differs from C. artus Kozlov and Kononova in the more flattened mesoscutum (C. artus with protruding mesoscutum) and the sculpture of the metasomal tergites (in C. stellae, only petiolus and tergite II striate, while in C. artus, such striation present on tergites I–IV). C. stellae was reared from eggs of unidentified Orthoptera. C. recens is closely related to C. parilis Kononova. It can be distinguished by the fore-wing venation (C. recens has stigmal vein, which is twice as long as marginal vein and 0.66 times as long as postmarginal one; stigmal vein of C. parilis is 3 times as long as marginal vein and 0.83 times as long as postmarginal one), by the sculpture of the metasoma, and coloration of the coxae (yellow in C. recens and black in C. parilis). C. floridum is similar to C. mediterranea Kieffer, but can be identified by the length of the postmarginal vein, which is 3 times as long as the stigmal vein, whereas C. mediterranea has the postmarginal vein, which is only twice as long as the stigmal one. C. floridum also differs in the sculpture of the metasoma (C. floridum has all the metasomal tergites with longitudinal lines, while C. mediterranea has only metasomal petiolus with the same sculpture and tergites II–IV with alveolate sculpture, tergites V and VI are slightly stippled) and in the coloration of the legs, which are yellow (as coxae), while C. mediterranea has brownish black legs. C. parilis resembles C. recens, but differs from it in the fore-wing venation, sculpture of the metasoma, and coloration of the coxae. C. ordo differs from the closely related C. ruficollis Kozlov et Kononova in the head sculpture, which is finely alveolate in C. ordo and finely granulate in C. ruficollis. Oxyscelio florum is closely related to O. perpensum, but differs from it in the coloration of the body and size of the antennal segments, stigmal and postmarginal veins, and metasomal tergites. O. perpensum is closely related to O. florum. The main distinguishing morphological characters are similar to those in O. florum. O. perpensum was reared from eggs of unidentified Orthoptera.     

Host location and oviposition in a basal group of parasitic wasps: the subgenual organ, ovipositor apparatus and associated structures in the Orussidae (Hymenoptera, Insecta)

Anatomical studies and behavioural observations indicate that representatives of the Orussidae use vibrational sounding to detect suitable oviposition sites. During host location, vibrations generated by tapping the tips of the antennae against the wood are picked up by the fore legs through the basitarsal spurs, transmitted along the basitarsi to thin-walled areas on the tibiae and through haemolymph to the subgenual organs, where they are transduced into nerve impulses. The apical antennomeres are distinctly shaped and have the cuticle thickened distally. The fore basitarsi have weakly sclerotised basitarsal lines proximally and membranous basitarsal spurs distally. The external wall of the fore tibiae have thin-walled areas distally on their posterior parts. Internally, large subgenual organs are situated opposite the thin-walled areas and each organ consists of 300–400 scolopidial units suspended between a lateral cuticular spine, a ventral sheet and a median ridge. The ovipositor is several times the length of the body of the wasp. When at rest, it extends all the way into the prothorax, where it is coiled before extending posteriorly to lie between the third valvulae distally. The ovipositor lies in a membranous ovipositor sac attached posteriorly to the proximal parts of the ovipositor apparatus and the posterior margin of sternum 7. In the ovipositor apparatus, the anterior parts of the second valvifers are displaced and expanded anterodorsally, inverting the first valvifers and the base of the ovipositor. When in use, the ovipositor is extended and retracted by median apodemes situated on the anterior margins of abdominal sterna 3–7. Longitudinal muscles between the apodemes allow the latter to grip the ovipositor in troughs between them. The ovipositor extends from the abdomen at the tip of sternum 7, and an internal trough on sternum 7 serves to guide the ovipositor into the wood. Despite the alterations observed in the ovipositor apparatus in the Orussidae, the musculature is almost complete and the mode of operation presumably not much different from that of other representatives of the Hymenoptera. The different ways parasitic wasps with very long ovipositors handle and accommodate these and the implications for the evolutionary history of Hymenoptera are discussed. Accepted: 14 March 2001