Wasp Larvae Research Articles

Laticifer distribution in fig inflorescence and its potential role in the fig-fig wasp mutualism

Although in Moraceae the presence of laticifers is considered to be a synapomorphy, little is known about the distribution and morphology of this type of secretory structure in the reproductive organs of its species. Ficus, the largest genus of Moraceae, is characterized by an inflorescence known as syconium and by an obligate mutualistic interaction with pollinating wasps. The objectives of the present study were to evaluate the distribution and morphology of laticifers in syconia of 36 species belonging to different Ficus sections and to survey traits of taxonomic and adaptive value for the group. Syconia containing flowers in a receptive state were collected, fixed and processed for anatomical analysis. All species studied have branched laticifers distributed in the syconium receptacle, in the ostiolar bracts and in the pedicel of staminate flowers. Almost all species show laticifers in the pedicel of shorter-styled flowers. Laticifers also occur in the pedicel of longer-styled flowers in most Ficus sections, except F. curtipes (Conosycea section) and more than 75% of the studied species of the Americanae section. Laticifers are observed in the sepals of 25 of the 36 species studied and occasionally in the pistil. The presence of laticifers in the pedicel of shorter-style flowers and its absence in the pistil suggest that the distribution of this secretory structure in the fig flower was selected by pressures imposed by the fig-fig wasp mutualism. The laticifers in the pedicel of shorter-styled flowers may confer protection to the developing wasp larvae against natural enemies. However, the absence of laticifers in the pistil of most Ficus species studied was probably selected by the mutualistic relationship with the agaonid pollinating wasps since the latex could interfere with oviposition through the style, with the larval development of the pollinating fig wasps, and the emergence of pollinator offspring from their galls.

Venom is beneficial but not essential for development and survival of Nasonia.

Parasitoid wasps sting and inject venom in arthropod hosts, which alters host metabolism and development while keeping the host alive for several days, presumably to induce benefits for the parasitoid young.Here we investigate the consequences of host envenomation on development and fitness of wasp larvae in the ectoparasitoid Nasonia vitripennis, by comparing wasps reared on live unstung, previously stung, and cold-killed hosts. Developmental arrest and suppression of host response to larvae are major venom effects that occur in both stung and cold-killed hosts, but not unstung hosts; while cold-killed hosts lack venom effects that require a living host. Thus, cold-killed hosts mimic some of the effects of venom, but not others.Eggs placed on live unstung hosts have significantly higher mortality during development, however successfully developing wasps from these hosts have similar lifetime fecundity to wasps from cold-killed or stung hosts. Therefore, although venom is beneficial, it is not required for wasp survival.While wasps developing on cold-killed versus stung hosts have similar fitness, multiple generations of rearing on cold-killed hosts results in significant fitness reductions of wasps.We conclude that the largest benefits of venom are induction of host developmental arrest and suppression of host response to larva (e.g. immune responses), although more subtle benefits may accrue across generations, or under stressful conditions.

Wasp venom evolution

Evolutionary Biology![Figure][1] Parasitoid wasps have evolved venoms for host control. PHOTO: HUTTON/TOM STACK ASSOC/ALAMY STOCK PHOTO Parasitoid wasps use venom to immobilize their hosts and manipulate them into providing a suitable environment for the growth of wasp larvae. In response to changes in host ranges and availability, venom genes need to evolve rapidly to maintain efficacy. Martinson et al. studied the sequence and expression of venom genes in closely related wasp species to determine how they evolve. The authors found that many of these genes do not evolve through duplication and neofunctionalization, as expected, but rather are the result of co-opting single-copy genes of different functions. Similarly to genes that have lost venom function, these new venom genes are not a consequence of alterations in the gene sequence itself, but instead have modified cis-regulated expression patterns. Curr. Biol. 10.1016/j.cub.2017.05.032 (2017). [1]: pending:yes

Patterns of temporal and enemy niche use by a community of leaf cone moths (Caloptilia) coexisting on maples (Acer) as revealed by metabarcoding.

The diversity of herbivorous insects is often considered a function of host plant diversity. However, recent research has uncovered many examples of closely related herbivores using the same host plant(s), suggesting that partitioning of host plants is not the only mechanism generating diversity. Herbivores sharing hosts may utilize different parts of the same plant, but such resource partitioning is often not apparent; hence, the factors that allow closely related herbivores to coexist are still largely undetermined. We examined whether partitioning of phenology or natural enemies may explain the coexistence of leaf cone moths (Caloptilia; Gracillariidae) associated with maples (Acer; Sapindaceae). Larval activity of 10 sympatric Caloptilia species found on nine maple species was monitored every 2-3weeks for a total of 13 sampling events, and an exhaustive search for internal parasitoid wasps was conducted using high-throughput sequencing. Blocking primers were used to facilitate the detection of wasp larvae inside moth tissue. We found considerable phenological overlap among Caloptilia species, with two clear peaks in July and September-October. Coexisting Caloptilia species also had largely overlapping parasitoid communities; a total of 13 chalcid and ichneumon wasp species attacked Caloptilia in a nonspecific fashion at an overall parasitism rate of 46.4%. Although coexistence may be facilitated by factors not accounted for in this study, it appears that niche partitioning is not necessary for closely related herbivores to stably coexist on shared hosts. Co-occurrence without resource partitioning may provide an additional axis along which herbivorous insects attain increased species richness.

Biology, Prey, and Levels of Prey Paralyzation byCerceris fumipennisSay (Hymenoptera: Crabronidae) in New Hampshire

ABSTRACT: Cerceris fumipennis is a colonial wasp that preferentially preys on native and nonnative Buprestidae, which includes emerald ash borer (EAB), Agrilus planipennis. EAB is currently a major threat to ash tree (Fraxinus spp.) populations in the northeast United States and parts of Canada, and C. fumipennis is used for bio-surveillance of this destructive pest. This wasp catches, stings, and paralyzes buprestid and other beetles that then serve as a live food source for the wasp larvae. Two large colonies of C. fumipennis were monitored during the summer of 2013 in Merrimack County, NH, USA, to determine seasonality of C. fumipennis and to document the prey species and the levels of paralyzation of these species. There were 853 individuals consisting of 34 buprestid species and one chrysomelid species taken from C. fumipennis females. Eleven of these species had paralyzation rates of less than 100%, consisting of 11% of the total collected prey. Chrysobothris verdigripennis, Agrilus carpini, Actenod...

Style length variation in male and female figs: development, inheritance, and control of pollinator oviposition

AbstractFig trees (Ficus spp., Moraceae) depend on female fig wasps to transport their pollen and as a reward provide nutrition for pollinator fig wasp larvae. Most pollinators are host specific, but natural plant hybrids occur if atypical hosts are pollinated. Female fig wasps lay their eggs into ovaries of female flowers in receptive figs by inserting their ovipositors through the styles, and relative style and ovipositor lengths are believed to largely determine their ability to oviposit. In dioecious fig trees, flowers in receptive male figs have short styles and support larval development, whereas flowers in receptive female figs have long styles and only develop into seeds. Using the dioecious fig tree species Ficus montana Burm. f. and Ficus asperifolia Miq., we recorded the comparative ontogeny of style lengths to determine whether style growth in the two sexes is coordinated with the attraction of pollinators, and how maximum style lengths relate to the ovipositor lengths of their pollinators. F1 hybrids between these species produce viable seeds, but no pollinator offspring. We examined style lengths in F1s and backcrosses, relative to those of their parents, and whether coordination of style growth with pollinator attraction is disrupted. The ovipositor of Kradibia tentacularis (Grandi) (Hymenoptera: Agaonidae), the pollinator of F. montana, could reach some of the ovaries in female figs, but fails to lay eggs there. Styles in male F1 figs were intermediate in length between those of the two parents, but in female F1 figs styles grew longer than in either parent. Maximum style lengths in F1s were partially decoupled from receptivity, especially in female figs. Our results illustrate how timing of stigmal growth is coordinated with pollinator attraction, and that this coordination can be disrupted in hybrid individuals.

Selective resource allocation may promote a sex ratio in pollinator fig wasps more beneficial for the host tree

Mutualisms play a key role in most ecosystems, yet the mechanisms that prevent overexploitation of the mutualistic relationship are still poorly understood. In the mutualism between fig trees and their pollinating wasps both partners depend on each other. Fig trees benefit from female wasps that disperse their pollen, whereas wasps frequently benefit from a higher ratio of male offspring. Here we use manipulative field experiments to address whether host trees (Ficus racemosa) can influence the offspring sex ratio of the pollinator wasp. We controlled wasp matings; virgin wasps can lay only male eggs. We found that virgin foundress wasps had fewer offspring than mated foundresses. This was not caused by virgin wasps having a shorter lifespan, or laying fewer eggs. Instead, male wasp larvae were more likely to die during development. Additionally, male eggs were deposited in flowers of equal style length to those of female eggs, yet emerged from galls with shorter pedicels than those of female wasps. We suggest that male larvae are either allocated less resources by the tree, or are less able to attract resources, during development. If the tree orchestrates this difference it would promote a more female-biased wasp brood, thus increasing the tree’s fitness.

Two species of tanagers (Passeriformes: Thraupidae) forage on army ant workers (Eciton burchellii) carrying immature paper wasps.

ABSTRACT Eciton burchellii is a Neotropical army ant that consumes a variety of arthropods captured during swarm raids. Wasp larvae and pupae provide an important food source for E. burchellii, and this ant species is thought to be a major predator on immature wasps in many Neotropical areas. Some birds also prey on wasp brood. Numerous bird species regularly follow E. burchellii swarms but are thought to typically avoid eating army ants. Rather, the birds feed on the arthropods that the ant swarms flush from the leaf litter. I report observations of ant-following birds, the Gray-headed Tanager Eucometis penicillata and the Flame-colored Tanager Piranga bidentata consuming E. burchellii workers that were carrying Polistinae wasp larvae and pupae. It has been suggested that ant-following birds may impose a cost to army ants by consuming arthropods and competing with ants for food resources. Also, it has been speculated that army ants emigrate at night to avoid the loss of their brood to birds, but lack of ...

Oviposition Behavior and Survival of Tamarixia radiata (Hymenoptera: Eulophidae), an Ectoparasitoid of the Asian Citrus Psyllid, Diaphorina citri (Hemiptera: Liviidae), on Hosts Exposed to an Entomopathogenic Fungus, Isaria fumosorosea (Hypocreales: Cordycipitaceae), Under Laboratory Conditions.

Antagonistic interactions between the nymphal parasitoid, Tamarixia radiata Waterston (Hymenoptera: Eulophidae), and the ARSEF 3581 strain of the entomopathogenic fungus, Isaria fumosorosea Wize (Hypocreales: Cordycipitaceae), could disrupt biological control of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae). Three interactions were evaluated under laboratory conditions at 25 °C: 1) parasitoid survival if parasitized hosts were exposed to ARSEF 3581 blastospores before or after host mummification; 2) parasitoid survival if mummies containing larva or pupa were exposed to ARSEF 3581 hyphae; 3) parasitoid oviposition on infected hosts with visible or without visible hyphae. Topical application of blastospore formulation onto the dorsal surfaces of live nymphs parasitized with second-instar wasp larva (3 d after parasitism) reduced host mummification by 50% and parasitoid emergence by 85%. However, parasitoid emergence was not affected by topical application of blastospore formulation onto mummies that contained fourth-instar wasp larva (6 d after parasitism). Parasitoid emergence was reduced by 80% if mummies containing fourth-instar wasp larva were covered with blastospore formulation colonized by fungal hyphae. In comparison, parasitoid emergence was not affected if mummies containing wasp pupa (9 d after parasitism) were covered with formulation colonized by fungal hyphae. Female parasitoids oviposited on infected hosts without visible hyphae but not on infected hosts with visible hyphae. Our findings suggest that I. fumosorosea could detrimentally affect T. radiata, if both natural enemies are simultaneously deployed for biological control of D. citri However, temporal separation of the fungus and parasitoid could reduce antagonism and enhance control of D. citri.

The Role of Lipid Competition for Endosymbiont-Mediated Protection against Parasitoid Wasps in Drosophila.

ABSTRACTInsects commonly harbor facultative bacterial endosymbionts, such as Wolbachia and Spiroplasma species, that are vertically transmitted from mothers to their offspring. These endosymbiontic bacteria increase their propagation by manipulating host reproduction or by protecting their hosts against natural enemies. While an increasing number of studies have reported endosymbiont-mediated protection, little is known about the mechanisms underlying this protection. Here, we analyze the mechanisms underlying protection from parasitoid wasps in Drosophila melanogaster mediated by its facultative endosymbiont Spiroplasma poulsonii. Our results indicate that S. poulsonii exerts protection against two distantly related wasp species, Leptopilina boulardi and Asobara tabida. S. poulsonii-mediated protection against parasitoid wasps takes place at the pupal stage and is not associated with an increased cellular immune response. In this work, we provide three important observations that support the notion that S. poulsonii bacteria and wasp larvae compete for host lipids and that this competition underlies symbiont-mediated protection. First, lipid quantification shows that both S. poulsonii and parasitoid wasps deplete D. melanogaster hemolymph lipids. Second, the depletion of hemolymphatic lipids using the Lpp RNA interference (Lpp RNAi) construct reduces wasp success in larvae that are not infected with S. poulsonii and blocks S. poulsonii growth. Third, we show that the growth of S. poulsonii bacteria is not affected by the presence of the wasps, indicating that when S. poulsonii is present, larval wasps will develop in a lipid-depleted environment. We propose that competition for host lipids may be relevant to endosymbiont-mediated protection in other systems and could explain the broad spectrum of protection provided.

Diapause and Cold Hardiness of the Almond Wasp, Eurytoma amygdali (Hymenoptera: Eurytomidae), Two Independent Phenomena.

The almond wasp, Eurytoma amygdali Enderlein (Hymenoptera: Eurytomidae), a key pest of almond, is a univoltine pest diapausing as last instar larvae inside the damaged fruits for almost nine months in a year. In this study, changes in the amount of total simple sugars, lipid, protein, glycogen, trehalose, glucose, supercooling points (SCPs), and cold hardiness of the diapausing larvae were measured from October to March for first year diapause-destined and in August and September for second year diapause-destined larvae. Changes in glycogen content were reversely proportional to changes in total simple sugars and low molecular weight carbohydrates. These changes reflect the interconversion of glycogen to sugar alcohol in order to increase the insect cold tolerance. We found that cold hardiness and diapause of the last instar larvae of the almond wasp have evolved separately. Cold hardiness was highly associated with physiological changes (accumulation of cryoprotectants), but no physiological changes occurred in early diapause of first year diapause-destined and second year diapause-destined larvae. The almond wasp larvae were found to be a freeze-avoidant insect, as no larva survived after SCP determination and crystallization of its body fluids.

The Feather Structure of Oriental Honey Buzzards (Pernis ptilorhynchus) and Other Hawk Species in Relation to Their Foraging Behavior.

The basic structure of a bird feather may be adapted to suit a variety of functions on different parts of the body and in different species. In Oriental honey buzzards (Pernis ptilorhynchus), a species which often preys on the larvae of bees and wasps, it is thought that the bird's integument may provide protection against the stings of these insects. We investigated the structure of Oriental honey buzzard feathers from the face, head, and neck using light and scanning electron microscopy. The structure and appearance of the feathers were compared with those of two other hawk species which live in similar habitats but have different diets: the grey-faced buzzard (Butastur indicus) and the black kite (Milvus migrans). All feathers of Oriental honey buzzards that were examined were smaller than feathers from the same regions of the body of other species and had a reduced number of plumulaceous barbs; barbs were also closer together at the feather tip and had a high barbule density. The small 'scale feathers' on the face had deep barbules with a curved, armor-like appearance, which may help prevent stings from reaching the skin. A unique filamentous substance was observed on all the honey buzzard feathers, particularly those from around the eye of a male bird. It is possible that this may be related to a chemical defense mechanism to deter bees and wasps.

Life history of the spider parasitoid Zatypota percontatoria (Hymenoptera: Ichneumonidae)

AbstractThe life history of polysphinctine parasitoids is poorly understood. As a result, their effect on their host has not been evaluated. Here, we present the phenology of Zatypota percontatoria, an ectoparasitoid wasp of theridiid spiders, using rich field, semi‐field and laboratory investigations of selected life‐history parameters. The wasps overwintered as larva attached to the spider abdomen and the imagos of the first generation emerged at the beginning of May. The sex ratio (F/M) of overwintered wasp larvae was 1.4. The wasp spent an average of 6.4 days in the egg stage, 27.67 days in the larval stage and 9.6 days in the pupal stage. Adult longevity was on average 14.34 days. Oviposition occurred on average 8.44 days following maturity. The wasp laid on average 0.35 eggs/day. The total fecundity was on average 7.4 eggs per wasp and decreased with age (data from unmated females). The developmental rate increased with experimental temperature up to 28 °C. The lower developmental threshold for pupae was estimated at 6.6 °C. The sum of effective temperatures for pupae was estimated at 157.8 degree days. Using daily temperature records from the Czech Republic over the last 41 years, we estimated an average of 3.5 generations of Z. percontatoria per year. Mortality was 48% in semi‐field conditions and 23% in the laboratory. The incidence of mortality was highest during egg and larval stages caused by the detachment of eggs or larvae during spider molting, the mortality of the spider‐host and egg deposition on the spider prosoma.

Differences in the reproductive durations of Myzus persicae (Hemiptera: Aphididae) parasitized by three aphidiid parasitoids

The reproductive durations of Myzus persicae (Sulzer) after parasitization by three species of Aphidiinae were compared and the mechanisms for differences in duration were examined. The lifetime fecundities of adult aphids parasitized by Aphidius colemani Viereck, Aphidius gifuensis Ashmead, and Diaeretiella rapae (McIntosh) were 3.96, 6.40, and 6.48, respectively. These values were much smaller than that of healthy adults (61.43 nymphs). The time of termination of reproduction by the aphids coincided with the time that the parasitic wasp larvae reached second instar. We infer that first-instar larvae of all three species initially attack conspecific and/or heterospecific competitors and that consumption of the aphid’s ovaries and other reproductive organs commences in the second instar. The modified intrinsic rates of natural increase (rparasitized) calculated from post-parasitized fecundity were 0.185 by A. colemani, 0.233 by A. gifuensis, and 0.234 by D. rapae. Parasitization of 100 % of the adult aphids by A. gifuensis or D. rapae decreased the growth rate to a minimum of 24.4 % while A. colemani more moderately suppressed the growth of the aphid population (39.9 %). We propose the possibility that the effectiveness of species of Aphidiinae as biological control agents is influenced by differences in the duration of aphid reproduction following parasitization.

The parasitic wasp Cotesia congregata uses multiple mechanisms to control host (Manduca sexta) behaviour.

Some parasites alter the behaviour of their hosts. The larvae of the parasitic wasp Cotesia congregata develop within the body of the caterpillar Manduca sexta During the initial phase of wasp development, the host's behaviour remains unchanged. However, once the wasps begin to scrape their way out of the caterpillar, the caterpillar host stops feeding and moving spontaneously. We found that the caterpillar also temporarily lost sensation around the exit hole created by each emerging wasp. However, the caterpillars regained responsiveness to nociception in those areas within 1 day. The temporary reduction in skin sensitivity is probably important for wasp survival because it prevents the caterpillar from attacking the emerging wasp larvae with a defensive strike. We also found that expression of plasmatocyte spreading peptide (PSP) and spätzle genes increased in the fat body of the host during wasp emergence. This result supports the hypothesis that the exiting wasps induce a cytokine storm in their host. Injections of PSP suppressed feeding, suggesting that an augmented immune response may play a role in the suppression of host feeding. Injection of wasp larvae culture media into non-parasitized caterpillars reduced feeding, suggesting that substances secreted by the wasp larvae may help alter host behaviour.

Sphecid wasp larvae feeding on large-sized cockroaches in a dead wood cavity

We investigated the nest site and prey items of Isodontia auripygata (Hymenoptera: Sphecidae) in a subtropical forest on Iriomote Island, ca. 200 km east of Taiwan. I. auripygata used the cavity of a dead branch as their nest site, and the nest was composed of two cells that were divided by wood offcuts. Inside the branch, we found large-sized adult cockroaches, Rhabdoblatta formosana (Blattodea: Epilampridae), R. formosana adults were fed to an I. auripygata larva in each cell. To our knowledge, this is the third record of species of the genus Isodontia that prey on cockroaches.

Chemical Strategies of the Beetle Metoecus Paradoxus, Social Parasite of the Wasp Vespula Vulgaris.

The parasitoid beetle Metoecus paradoxus frequently parasitizes colonies of the common wasp, Vespula vulgaris. It penetrates a host colony as a larva that attaches itself onto a foraging wasp's body and, once inside the nest, it feeds on a wasp larva inside a brood cell and then pupates. Avoiding detection by the wasp host is crucial when the beetle emerges. Here, we tested whether adult M. paradoxus beetles avoid detection by mimicking the cuticular hydrocarbon profile of their host. The beetles appear to be chemically adapted to their main host species, the common wasp, because they share more hydrocarbon compounds with it than they do with the related German wasp, V. germanica. In addition, aggression tests showed that adult beetles were attacked less by common wasp workers than by German wasp workers. Our results further indicated that the host-specific compounds were, at least partially, produced through recycling of the prey's hydrocarbons, and were not acquired through contact with the adult host. Moreover, the chemical profile of the beetles shows overproduction of the wasp queen pheromone, nonacosane (n-C29), suggesting that beetles might mimic the queen's pheromonal bouquet.

Wasp masters manipulate web-building slaves

Some wasps have unpleasant habits. Hijacking an unsuspecting insect or spider, parasitic wasps incapacitate their hapless victims by taking control of their nervous systems and turning them into zombies. Once the wasp has its victim in its clutches, it deposits its egg on or within the victim's body, ready for the next generation to develop. Keizo Takasuka from Kobe University, Japan, explains that one particular wasp, Reclinervellus nielseni, turns its spider targets (Cyclosa argenteoalba) into drugged navvys whose final act is to construct a tough ‘cocoon’ web from the original orb web to protect the developing wasp pupa after the spider's death. According to Takasuka, C. argenteoalba produce several different styles of web over the course of their lives – ‘orb’ webs when hunting and ‘resting’ webs for protection when moulting – each produced by a specific set of behaviours. However, it wasn't clear which of the spider's behavioural patterns and web-types the wasp was adapting to its own ends.Intrigued, Takasuka headed to shrines in two nearby cities (Tamba and Sasayama) from mid-April to mid-May ready to collect spiders complete with their webs and parasitic larvae. However, Takasuka recalls that keeping the spiders alive in the lab before their zombie state was triggered was quite a challenge. Some refused to build webs in captivity and he occasionally destroyed the delicate structures when he inadvertently snagged supporting frame threads attached to distant objects. However, after weeks of patiently nurturing the spiders, he was rewarded when 10 obediently constructed cocoon webs for their parasite masters.Analysing the cocoon webs, Takasuka was struck by their similarity to the resting webs, complete with fluffy decorative structures. And when Takasuka analysed the spiders’ behaviour as they constructed the cocoon webs over a 10 h period, he saw that the manipulated spiders always constructed the new web on the site of the old orb web, painstakingly removing the sticky spiral first, then reinforcing the radial and frame threads and then adding the fibrous web decorations. And, when the web was complete and the wasp larva done with its spider slave, the larva directed the spider to return to the hub of the web before murdering it.So, the cocoon webs looked like resting webs, but were they true adaptions of the more conventional web? Takasuka and Kensuke Nakata photographed the webs in UV light and were impressed to see the fibrous decorations shining brightly, to deter other insects from inadvertently blundering into the pupa's nursery. And when Tomoki Yasui, Toru Ishigami and Takasuka investigated the strength of the different types of silk that contribute to the web's structure, they were amazed to see that the cocoon web was significantly tougher than the orb and resting webs: the breaking force of the cocoon radius and frame silks was 2.7–40 times greater than that of the orb and resting webs. However, the breaking stress of the silks was not increased significantly, leading Takasuka to suspect that instead of forcing the spiders to alter silk production, the wasp slave-masters were directing the spiders to lay down more fibres to strengthen the cocoon web, which is essentially a reinforced resting web.Explaining that parasitised spiders transition into zombie web building even when the parasitic larva has been removed, Takasuka also suggests that resting web construction is triggered by the same hormones that control moulting and he suspects that the larva may inject a substance similar to a moulting hormone into the hapless spider during the later stages of its stay, ready to trigger cocoon web building when the larva is ready to pupate.

Development ofMicroplitis similis(Hymenoptera: Braconidae) on Two Candidate Host Species,Spodoptera lituraandSpodoptera exigua(Lepidoptera: Noctuidae)

Microplitis similis Lyle (Hymenoptera: Braconidae) is a solitary endoparasitic braconid that generally parasitizes larvae of Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) and many other noctuid species. To understand host preference, fitness, and the effects of M. similis on the hosts, we compared percentage parasitism, development periods, and the effects on host growth in candidate noctuid species. We found high levels of parasitism of S. exigua and Spodoptera litura (F.) larvae but not of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) larvae. The parasitoid wasp larvae took similar amounts of time for development on S. exigua and S. litura larvae, i.e., 13.87 ± 0.15 and 13.69 ± 0.42 d, respectively. Compared with the control larvae, the growth and development of the hosts were severely affected. The hosts were able to molt to 4th instars after being parasitized as early 3rd instars, but were unable to develop to the 5th instar. The body weight was similar between parasitized and non-parasitized larvae within the first 4 d (3 d in S. litura) but later began to show a significant difference from the 5th day on (4th day in S. litura). The host larvae eventually weighed up to 50 to 80% less than the non-parasitized larvae. Furthermore, the host larvae lived for an extended period in the same instar after egression of the parasitoid, but the body mass did not increase.

Two types of embryos with different functions are generated in the polyembryonic wasp Macrocentrus cingulum (Hymenoptera: Braconidae)

In this study, we report that two types of embryos, normal and pseudogerm, are generated from a single egg of the polyembryonic larval endoparasitoid Macrocentrus cingulum (Braconidae). M. cingulum larvae develop in the host hemocoel, emerging from the host to pupate. After egg cleavage and embryo proliferation dozens of normal embryos and thousands of pseudogerms are generated in the host larva. The difference between normal embryos and pseudogerms is that the former develop into larvae while the latter do not. The primordium that develops in normal embryos is surrounded by an extraembryonic membrane that originates from the syncytium. Pseudogerms in contrast consist only of a syncytium containing many large nuclei and are continuously generated during embryonic development. Both pseudogerms and early embryos possess dense microvilli that function to absorb nutrients from the host. After eclosion wasp larvae produced from normal embryos feed on pseudogerms. Therefore, two types of embryos originating from the same egg serve different functions. These results contribute to our understanding of the development of polyembryonic parasitoids.