Morphology and mechanics of the ovipositor system of Ceratobaeus ashmead (Hymenoptera : Scelionidae) and related genera

This paper aims to describe the ovipositor system of Ceratobaeus spp. (Hymenoptera : Scelionidae), which is unlike that known for nearly all other parasitic Hymenoptera. It is invaginated into the body cavity and is detached from the terminal segments of the metasoma (gaster). It is contained within a sclerotized membranous tube and is connected to the posterior metasoma only by elongated muscles and apodemes. However, the ovipostor of Ceratobaeus appears to operate in essentially the same manner as has been described for other insects. A model for the mechanics of ovipositor movement, including extension and retraction from the body cavity, is proposed. Observations on ovipositional behaviour and morphology of the system provide support for the proposed model. Closely related genera (Idris, Hickmanella and Baeus) have ovipositor systems that are very similar in structure to Ceratobaeus. Only Odontacolus has an ovipositor that differs substantially from the previous genera, although it is also thought to be closely related to this group. The anatomy, mechanics, and evolution of the hymenopteran ovipositor are discussed in the light of the present study.     

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.     

Multiple infestation by seed predators: the effect of loculate fruits on intraspecific insect larval competition

Many morphological features of fruits are important factors affecting predispersal seed predation by insects. This paper analyses the predispersal seed predation process of a major predator (a Noctuidae lepidopteran larvae) in loculate fruits of a bushy perennial plant, Cistus ladanifer. The main aim of the study is to assess the potential effect of internal valvae (which partition groups of seeds) in the intraspecific competition between larvae in multiple-infested fruits.Our results show that larvae do not reject already infested fruits, but they avoid the proximity of other larvae within the fruit, keeping an average minimum distance of one locule. In multiple-infested fruits, larval mortality increases and the proportion of seeds consumed by each larvae decreases. In those situations in which valvae keep apart larvae within a fruit, these only suffer the cost of exploitation competition with a low acquisition of resources. However, when all valvae between them are pierced by the larvae, competition switches to an interference component and larval mortality increases markedly. The existence of valvae within a fruit allows larvae to diminish the cost of intraspecific competition, obtaining high life expectancies (70%), even in triple-infested fruits.     

Ovipositor morphology correlates with life history evolution in agaonid fig wasps

The high adaptive success of parasitic Hymenoptera might be related to the use of different oviposition sites, allowing niche partitioning among co-occurring species resulting in life history specialization and diversification. In this scenario, evolutionary changes in life history and resources for oviposition can be associated with changes in ovipositor structure, allowing exploitation of different substrates for oviposition. We used a formal phylogenetic framework to investigate the evolution of ovipositor morphology and life history in agaonid wasps. We sampled 24 species with different life histories belonging to all main clades of Agaonidae including representatives of all described genera of non-pollinating fig wasps (NPFW). Our results show an overall correlation between ovipositor morphology and life history in agaonid fig wasps. Ovipositor morphologies seem to be related to constraints imposed by features of the oviposition sites since ovipositor morphology has experienced convergent evolution at least four times in Sycophaginae (Agaonidae) according to the resource used. Non-galling species have more distantly spaced teeth with uneven spacing, as opposed to the observed morphology of galling species. Our results suggest that the ancestral condition for ovipositor morphology was most likely the presence of one or two apical teeth. Regarding life history, ovary galling species that oviposit in receptive figs possibly represent the ancestral condition. Different ovipositor characteristics allow exploitation of new niches and may be related to resource partitioning and species co-existence in the fig-fig wasp system.     

Manganese and zinc in the ovipositors and mandibles of hymenopterous insects

X-ray microanalysis of the ovipositor and mandibles of various hymenopterous insects has revealed the presence in many species of up to 10% wt/wt of either zinc or manganese in the cuticle. These metals appear to be involved in cuticular hardening, so helping to reduce abrasive wear. Zinc is found in the ovipositors of most Siricidae, Stephanoidea, and Chalcidoidea. In Ichneumonoidea and Cynipoidea, the metal involved is manganese. Megalyroidea are unique in the Hymenoptera in having both zinc and manganese in their ovipositors, though in different locations. Except for Bethylidae, no metals were detected in the ovipositors or stings of species that penetrate soft substrates or do not make holes at all. The cutting edge of the mandibles of many insects that chew their way through hard substrates during egress from their pupation sites almost invariably contain high concentrations of zinc, and this is present in many that lack metals in their ovipositor. The phylogenetic and ecological implications of metal occurrence are discussed.     

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.     

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.     

The eggshell of the almond wasp Eurytoma amygdali (Hymenoptera, Eurytomidae) - 1. Morphogenesis and fine structure of the eggshell layers

The almond wasp Eurytoma amvgdali (Hymenoptera: Eurytomidac) feeds and oviposits exclusively in almonds and therefore is characterized as an insect of economic importance. Its meroistic polytrophic ovaries include follicles with a tri-partitc configuration. The mature follicles exhibit two filaments occupying the two poles of the egg. One is the micropylar filament while the other might serve for respiration since it is likely that its flattened end layers remain outside the almond fruit. The eggshell is formed by aposition and the follicle cells, which surround the follicle until the end of oogenesis, may be responsible for protein synthesis and secretion which finally lead to the assembly of the eggshell. The eggshell comprises the thin vitelline membrane, possibly a 'wax' layer of waterproofing function, a transluscent layer which appears amorphous even at the end of choriogenesis, a granular layer, including large and small electron-dense granules, and finally a columnar layer very similar to layers found in other insect species of the same or different orders. Peroxidase is histochemicalLY found for the first time in an eggshell of the Hymenoptera order: the tranluscent layer in particular is positively stained (electron-dense). Two possible roles of this peroxidatic activity are discussed, first, in comparison to other fruit-infesting insects, we assume that elastic chorion is produced through the function of peroxidase induced bonds (resilin-type bonds), very important for avoiding premature breaking, while being oviposited through a narrow ovipositor. Second, referring to other studies, this layer can play a bactericidal role for additional embryonic itprotection.     

Sex,life history and morphology drive individual variation in flight performance of an insect parasitoid

1. The movement of organisms can be driven by multiple factors and has implications for fitness and the spatial distribution of populations. Insects spend a large proportion of their adult lives foraging by flying for resources; however, their capability and motivation to move can vary across individuals. 2. The aims of this study were to examine interindividual and sex differences in flight performance and flight characteristics, using a flight mill bioassay, in Megarhyssa nortoni (Hymenoptera; Ichneumonidae), a parasitoid of the invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae), one of the most important pests of pine afforestation worldwide. We also assessed the influence of morphological traits in combination with sex on flight and explored the cost of flight on longevity and mass loss. 3. The results show a difference between sexes in flight characteristics and performance. Females show greater total distance flown than males, and have a better capacity to undergo sustained flight. Sexual size dimorphism was also found and it was noted that size positively affects distances travelled. Females have a longer life span than males, yet no differences were noted in longevity within sex between individuals that did not fly and those that flew. Age did not influence flight performance of females or impacted on post‐flight longevity. Females lost less body mass than males even after flying longer distances. 4. These results suggest that sex‐specific behaviours probably govern flight abilities together with (and not only because of) morphological traits. The paper discusses sex‐specific life‐history strategies in parasitoids and their implications for biocontrol programmes.     

Quantifying interspecific variation in dispersal ability of noctuid moths using an advanced tethered flight technique

Dispersal plays a crucial role in many aspects of species' life histories, yet is often difficult to measure directly. This is particularly true for many insects, especially nocturnal species (e.g. moths) that cannot be easily observed under natural field conditions. Consequently, over the past five decades, laboratory tethered flight techniques have been developed as a means of measuring insect flight duration and speed. However, these previous designs have tended to focus on single species (typically migrant pests), and here we describe an improved apparatus that allows the study of flight ability in a wide range of insect body sizes and types. Obtaining dispersal information from a range of species is crucial for understanding insect population dynamics and range shifts. Our new laboratory tethered flight apparatus automatically records flight duration, speed, and distance of individual insects. The rotational tethered flight mill has very low friction and the arm to which flying insects are attached is extremely lightweight while remaining rigid and strong, permitting both small and large insects to be studied. The apparatus is compact and thus allows many individuals to be studied simultaneously under controlled laboratory conditions. We demonstrate the performance of the apparatus by using the mills to assess the flight capability of 24 species of British noctuid moths, ranging in size from 12–27 mm forewing length (~40–660 mg body mass). We validate the new technique by comparing our tethered flight data with existing information on dispersal ability of noctuids from the published literature and expert opinion. Values for tethered flight variables were in agreement with existing knowledge of dispersal ability in these species, supporting the use of this method to quantify dispersal in insects. Importantly, this new technology opens up the potential to investigate genetic and environmental factors affecting insect dispersal among a wide range of species.     

GENETIC CORRELATIONS AMONG TRAITS DETERMINING MIGRATORY TENDENCY IN THE SAND CRICKET,GRYLLUS FIRMUS

Migration by flight is an important component of the life cycles of most insects. The probability that a given insect will migrate by flight is influenced by many factors, most notably the presence or absence of fully-developed wings and functional flight musculature. Considerable variation has also been reported in the flight propensity of fully-winged individuals with functional flight musculature. We test the hypothesis that these components of migratory tendency are genetically correlated in a wing-dimorhic cricket, Gryllus firmus. Flight propensity and condition of the dorsal longitudinal flight muscles (DLM) are examined in fully-winged (LW) crickets from lines selected for increasing and for decreasing %LW, as well as from unselected control lines. Increased %LW is found to be associated with increased flight propensity among individuals with intact DLM, and with retention of functional DLM. The opposite is true for lines selected for decreased %LW. These results indicate both phenotypic and genetic correlations among behavioral, physiological, and morphological traits determining migratory tendency. We propose that these correlations may result from the multifunctional role of juvenile hormone, which has been reported to influence wing development, flight muscle development and degeneration, and flight propensity. Finally, we discuss the potential influence of genetic correlations for migratory traits on the evolution and maintenance of migratory polymorphisms in insects.     

Inferring life history from ovipositor morphology in parasitoid wasps using phylogenetic regression and discriminant analysis

Our understanding of the critical shift in life history among insect parasitoids from ectoparasitism to endoparasitism is hindered by the fact that this particular life history trait is not known for many phylogenetically important taxa. One method of coping with this problem is to seek correlations between the ovipositor structure and this life history trait among taxa whose life history is known, and then to use this to infer the trait in species whose life history in unknown. In one group of parasitoid wasps, the Ichneumonoidea (Hymenoptera), we scored a total of 20 morphometric and morphological characters of the ovipositor for 41 species whose life histories are known – representing all the main clades in which there have been independent transitions to endoparasitism plus a broad range of the ectoparasitoid groups; we then used phylogenetic regression and discriminant analyses to infer the life history of four species whose life histories are unknown. To allow for the effect of phylogenetic non-independence in the discriminant analysis, we carried out analyses using different randomly chosen representatives of the endoparasitoid clades (phylogenetic regression controls for phylogeny). These two methods gave congruent results from which we conclude that Megalohelcon and Gnamptodon are endoparasitoids, and Aspilodemon and Allobracon are ectoparasitoids. We discuss the consequences of these inferences for our understanding of the evolution of endoparasitism in the Ichneumonoidea.  © 2003 The Linnean Society of London. Zoological Journal of the Linnean Society , 2003, 139 , 213–228.     

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.     

The smallest insects evolve anucleate neurons

The smallest insects are comparable in size to unicellular organisms. Thus, their size affects their structure not only at the organ level, but also at the cellular level. Here we report the first finding of animals with an almost entirely anucleate nervous system. Adults of the smallest flying insects of the parasitic wasp genus Megaphragma (Hymenoptera: Trichogrammatidae) have only 339-372 nuclei in the central nervous system, i.e., their ganglia, including the brain, consist almost exclusively of processes of neurons. In contrast, their pupae have ganglia more typical of other insects, with about 7400 nuclei in the central nervous system. During the final phases of pupal development, most neuronal cell bodies lyse. As adults, these insects have many fewer nucleated neurons, a small number of cell bodies in different stages of lysis, and about 7000 anucleate cells. Although most neurons lack nuclei, these insects exhibit many important behaviors, including flight and searching for hosts.     

The cost of defense in social insects: insights from the honey bee

Defense is one of the most important factors affecting life history. The relationship of defense to life history traits as well as its possible costs has been reviewed extensively for many groups, including plants. However, defense in social insects, such as honey bees, has never been examined from a trade‐off perspective, although defense in honey bees, Apis mellifera L. (Hymenoptera: Apidae), has been widely studied. In this review, we discuss the life history traits of honey bees, particularly traits related to defense. We then examine trade‐offs in the context of resource availability. Lastly, we offer suggestions for future research on trade‐offs in honey bees and other social insects.     

Development of Microplitis croceipes as a biological sensor

Classical conditioning, a form of associative learning, was first described in the vertebrate literature by Pavlov, but has since been documented for a wide variety of insects. Our knowledge of associative learning by insects began with Karl vonFrisch explaining communication among honeybees, Apis mellifera L. (Hymenoptera: Apidae). Since then, the honey bee has provided us with much of what we understand about associative learning in insects and how we relate the theories of learning in vertebrates to insects. Fruit flies, moths, and parasitic wasps are just a few examples of other insects that have been documented with the ability to learn. A novel direction in research on this topic attempts to harness the ability of insects to learn for the development of biological sensors. Parasitic wasps, especially Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), have been conditioned to detect the odors associated with explosives, food toxins, and cadavers. Honeybees and moths have also been associatively conditioned to several volatiles of interest in forensics and national security. In some cases, handheld devices have been developed to harness the insects and observe conditioned behavioral responses to air samples in an attempt to detect target volatiles. Current research on the development of biological sensors with insects is focusing on factors that influence the learning and memory ability of arthropods as well as potential mathematical techniques for improving the interpretation of the behavioral responses to conditioned stimuli. Chemical detection devices using arthropod‐based sensing could be used in situations where trained canines cannot be used (such as toxic environments) or are unavailable, electronic devices are too expensive and/or not of sufficient sensitivity, and when conditioning to target chemicals must be done within minutes of detection. The purpose of this article is to provide a brief review of the development of M. croceipes as a model system for exploring associative learning for the development of biological sensors.     

Description and behavioural biology of two Ufens species (Hymenoptera: Trichogrammatidae), egg parasitoids of Homalodisca species (Hemiptera: Cicadellidae) in southern California

The morphology, distribution, and hosts of two egg parasitoids, Ufens principalis Owen sp. n. and U. ceratus Owen sp. n. (Hymenoptera: Trichogrammatidae), are described for the first time. These species are compared to U. niger (Ashmead), the only species of Ufens s. str. currently described from the Nearctic, and diagnostic differences are presented. The behavioural biology of U. principalis, and U. ceratus to a smaller extent, is also described for the first time. Ufens principalis exhibited a rapid and long-distance response in the form of directional flight toward freshly laid eggs of Homalodisca species, its primary hosts in southern California. Parasitism involved aggregations of female U. principalis on fresh Homalodisca egg masses, which remained attractive to U. principalis for a relatively short time. The level of oviposition by U. principalis females was low during most of the day and peaked before sunset in tandem with a peak in Homalodisca oviposition. Oviposition behaviour of U. principalis is described and the distribution of ovipositor probe durations showed that most probes were generally of very short duration. Mating of both Ufens species occurred on the egg mass, with males showing aggressive behaviour towards each other as they competed for emerging females. Ufens ceratus males displayed greater aggression towards other males than U. principalis males. By contrast, fights among U. principalis males involved more individuals and lasted longer than corresponding fights between U. ceratus males.     

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.     

Notes on ciliates (Protozoa,ciliophora) from Espeletia trees and Espeletia soils of the Andean Páramo,with descriptions of sikorops espeletiae nov. spec. and Fragmocirrus espeletiae nov. gen., nov. spec.

Melittobia hawaiiensis Perkins (Hymenoptera: Eulophidae), a common gregarious ectoparasitoid of aculeate Hymenoptera and other orders of insects, is reported for the first time as a parasitoid of Melitoma segmentaria (Fabricius) (Hymenoptera: Apidae) in Buenos Aires, Argentina.     

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.