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In order for successful biological pest control using parasitoids, the most suitable naturally available food resources, as well as the fitness of parasitoids feeding on these resources, need to be ascertained. The goal of this study was to improve the understanding of the ecological requirements and consequent fitness of one such parasitoid, Telenomus podisi Ashmead ( Hymenoptera: Platygastridae), a predominant stink bug ( Heteroptera: Pentatomidae) egg parasitoid native to southeastern USA. We assessed the effects of carbohydrate resources readily available in the wasp's natural habitat on longevity and fecundity of female T. podisi under laboratory conditions. Carbohydrate diets included in the study were buckwheat, Fagopyrum esculentum Moench ( Polygonaceae) nectar and honeydew from cowpea aphid, Aphis craccivora Koch ( Hemiptera: Aphididae), compared with honey or water controls, which are normally used for laboratory rearing of this species. Eggs of Podisus maculiventris Say ( Hemiptera: Pentatomidae) were provided as hosts for oviposition. Honeydew of cowpea aphid proved to be as good a nutrition source as buckwheat nectar, in enhancing wasp longevity and fecundity. We also assessed the importance of honeydew freshness on the biological attributes of T. podisi, as honeydew becomes crystallized or highly viscous on drying up and therefore may pose an issue for uptake by parasitoids. We found that fresh honeydew of the pea aphid, Acyrthosiphon pisum Harris ( Hemiptera: Aphididae) significantly enhanced wasp longevity when compared to a diet of 1-day-old honeydew and the fava bean leaf (control). However, fresh honeydew of green peach aphid, Myzus persicae Sulzer ( Hemiptera: Aphididae) had the same effect on wasp longevity, fecundity, and proportion of male progeny as radish leaf (control). The potential of certain ubiquitously available food resources, in enhancing biological control of economically damaging pests by parasitoids, is being highlighted in this study; information which could be valuable in similar parasitoid-host systems as well. [ABSTRACT FROM AUTHOR]

The introduction of invasive social wasp species of the genus Vespula ( Hymenoptera: Vespidae) to New Zealand has caused a major ecological problem, particularly in the beech forests ( Nothofagus spp.) of the South Island, where they have destabilized the native bird and invertebrate biodiversity. New attractants are under investigation as part of a search for pest management solutions. Fermenting brown sugar has been previously reported as a social wasp attractant. This work was undertaken to identify compounds from fermented brown sugar attractive to social wasps. Raw fermented brown sugar was confirmed to be attractive in a field trial and 10 chemical compounds present in the headspace were positively identified by coupled gas chromatography-mass spectrometry and synthetic references. During electroantennogram experiments, 3-methyl-1-butanol, 3-methylbutyl acetate, and ethyl hexanoate elicited high electrophysiological responses from Vespula vulgaris ( L.) antennae. These compounds mediated attraction of V. vulgaris wasps in forest margins by trapping. A blend of these compounds could be used as a lure in a monitoring tool, or even a local suppression method if combined with a toxin. [ABSTRACT FROM AUTHOR]

Mutualistic interactions between ants and Hemiptera are mediated to a large extent by the amount and quality of sugar-rich honeydew produced. Throughout the neotropics, the predaceous fire ant Solenopsis geminata ( Fabricius) ( Hymenoptera: Formicidae) is found in association with colonies of the pineapple mealybug, Dysmicoccus brevipes ( Cockerell) ( Hemiptera: Pseudococcidae), which they actively tend and protect from attack by natural enemies. In this study, we evaluate the effects of access to a sucrose solution on the mutualistic association between S. geminata and D. brevipes. Ten colonies of either species were established, with D. brevipes maintained on pumpkin, Cucurbita maxima Duchesne ( Cucurbitaceae), in screen cages. Five of the S. geminata colonies were permitted access to vials with 20% sucrose solution and a pumpkin with 20 adult mealybugs. The remaining ant colonies were allowed access to mealybug-infested pumpkins. Ant colonies with access to the sucrose solution attended mealybugs significantly less than those without additional sugar sources. Mealybug survival rates were similar under both treatments. Total body sugars and fructose were nearly twice as high in ants with access to honeydew and sucrose vs. those with access to honeydew and water. Fructose accumulated on the pumpkins over time in both treatments, suggesting that honeydew was not fully exploited by the ants. In conclusion, D. brevipes enjoy lower degrees of ant attendance when S. geminata have alternative sources of carbohydrates. We further discuss the significance of these findings for the conservation of predaceous ants and mealybug biological control. [ABSTRACT FROM AUTHOR]

Parasitoid survival and fecundity is generally enhanced with access to carbohydrate food sources. In many agricultural ecosystems, there is often a scarcity of suitable carbohydrates for parasitoids. This study compared the suitability of aphid honeydew and buckwheat nectar as diet for the aphid parasitoid Lysiphlebus testaceipes. Wasp lifespan and egg load were both increased with access to carbohydrates, but no differences were detected between the various carbohydrates diets tested. As aphid honeydew is a sufficient source of nutrition and L. testaceipes is a short-lived species, adding additional sources of carbohydrates like floral nectar strips to the agricultural landscape is unlikely to significantly increase the biological control exerted by L. testaceipes. [ABSTRACT FROM AUTHOR]

Honeydew from phloem-feeding insects and fruit fly insecticidal baits may serve as adult food resources for some insect species. In California (USA) olive orchards, the black scale [ Saissetia oleae (Olivier) (Hemiptera: Coccidae)] is a common honeydew producer, and spinosad-based fruit fly bait (GF-120) is used to control the olive fruit fly [ Bactrocera oleae (Rossi) (Diptera: Tephritidae)]. We investigated the effects of black scale honeydew and GF-120, as food resources, on adult foraging behaviour and survival of the olive fruit fly and two parasitoids in the olive agroecosystem: Scutellista caerulea (Fonscolombe) (Hymenoptera: Pteromalidae), a natural enemy of black scale, and Psyttalia humilis (Silvestri) (Hymenoptera: Braconidae), a parasitoid of the fruit fly. In food choice tests, female flies did not show a preference between GF-120 bait and honeydew, whereas male flies and the parasitoids we tested preferred honeydew. Adults of the three insect species readily fed on honeydew, but the natural enemies never ( P. humilis) or rarely ( S. caerulea) fed on GF-120 bait. Olfactometer tests further confirmed that the tested natural enemies were not attracted to GF-120 bait. The presence of honeydew significantly reduced fruit fly mortality when both honeydew and GF-120 were provided, compared with GF-120 given alone. A single meal of honeydew increased longevity in all insect species tested. The mean longevities of honeydew-fed insects were not significantly different from those feeding on clover honey. Our results suggest that the presence of honeydew would benefit the three insect species and may reduce the efficacy of GF-120 for fruit fly control because of preference of honeydew rather than fruit fly bait as a food resource. [ABSTRACT FROM AUTHOR]

Invasions by non-native insects can have important ecological impacts, particularly on island ecosystems. However, the factors that promote the success of invaders relative to co-occurring non-invasive species remain unresolved. For invasive ants, access to carbohydrate resources via interactions with both extrafloral nectary-bearing plants and honeydew-excreting insects may accelerate the invasion process. A first step towards testing this hypothesis is to determine whether invasive ants respond to variation in the availability of carbohydrate resources, and whether this response differs from that of co-occurring, non-invasive ants. We investigated the effect of carbohydrate subsidies on the short-term foraging and hemipteran-tending behaviours of the invasive ant Anoplolepis gracilipes (Formicidae) and co-occurring ant species on an extrafloral nectary-bearing plant by experimentally manipulating carbohydrate levels and tracking ant recruitment. We conducted experiments in 2 years at two sites: one site was invaded by A. gracilipes prior to 2007 and the other became invaded during the course of our study, allowing pre- (2007) and post-invasion (2009) comparisons. Short-term increases in carbohydrate availability increased the density of A. gracilipes workers on plants by as much as 400% and reduced tending of honeydew-excreting insects by this species by up to 89%, with similar responses across years. In contrast, ants at the uninvaded site in 2007 showed a weak and non-significant forager recruitment response. Across all sites, A. gracilipes workers were the only ants that responded to carbohydrate manipulations in 2009. Furthermore, ant-carbohydrate dynamics at a site newly invaded by A. gracilipes quickly diverged from dynamics at uninvaded sites and converged on those of the site with an established invasion. These findings suggest that carbohydrate resources may be particularly important for A. gracilipes invasions, and underscore the importance of species interactions, particularly putative mutualisms, in facilitating exotic species invasions. [ABSTRACT FROM AUTHOR]

As food items can vary in nutrient composition, diet selectivity can be an important trait to optimize nutrition. Most parasitoids depend as adults on various sugar-rich food sources such as nectar and honeydew. Nectar is often superior as a food source to honeydew, yielding higher parasitoid longevity. Little is known, however, of a preference parasitoids may have for one of these sugar sources and how this affects variation in their life-history traits. In this study, a combined empirical and modelling approach was adopted. First, it was investigated whether parasitoids show a feeding preference for nectar or honeydew in the laboratory and whether feeding history affects the preference of parasitoids. Second, using a process-based spatially explicit simulation model, it was evaluated how preference for nectar affects parasitoid life-history variables in fields with varying flower densities. The laboratory study revealed that naïve parasitoids showed no preference for either nectar or honeydew. However, when parasitoids had fed previously on honeydew and were then given the choice between nectar and honeydew, they preferred feeding on nectar to honeydew (with marginal statistical significance). Model simulations indicated that when nectar sources were present in the field, parasitoids that showed preference for nectar had a 1.3–1.8 times longer life span and parasitised up to 1.4 times more hosts than parasitoids that did not distinguish between honeydew and nectar. These combined empirical and modelling data suggest that aphid parasitoids may be able to discriminate between nectar and honeydew, and that a preference for nectar may enhance their longevity and reproduction in fields where nectar sources are available. [ABSTRACT FROM AUTHOR]

Feeding on sugar-rich foods such as nectar and honeydew is important for survival of many adult parasitoids. Especially in agricultural systems, honeydew is often the most prevalent carbohydrate source. However, relative to plant nectar, honeydew may be relatively unsuitable, as a result of an unfavourable sugar composition or the presence of secondary plant compounds. We studied survival of the aphid parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) on honeydew collected from various aphid species feeding on potato ( Solanum tuberosum L., cv. Desiree) (Solanaceae), wheat ( Triticum aestivum L., cv. Bobwhite) (Poaceae), or artificial diet, as well as the sugar composition of the different honeydews. Honeydews from the tested aphid species on potato, wheat, or artificial diet were found to be relatively suitable food sources for adult A. ervi, although not always as suitable as a 2 M sucrose solution. There were differences in honeydew sugar composition among the different aphid species on the various host plants. Multivariate statistics showed that the factor ‘aphid species’ had a significant influence on the sugar composition of the honeydew, explaining 27% of the variation in the potato system and 89% in the wheat system. When exploring the relationship between carbohydrate composition of the honeydews from aphids on potato and wheat plants, and their nutritional value for A. ervi, data revealed that differences in parasitoid longevity can to some extent be explained by carbohydrate composition. Furthermore, our results confirm that sucrose and its hexose components glucose and fructose are very suitable carbohydrate sources for hymenopteran parasitoids and show that parasitoid survival on an equimolar solution of the two monosaccharides glucose and fructose does not exceed performance on the disaccharide sucrose. [ABSTRACT FROM AUTHOR]

1. Many arthropods depend on carbohydrate-rich food sources such as nectar or honeydew. Nevertheless, we often know little about the extent to which various sugar sources contribute to the diet of arthropods. 2. One way to study food use in the field is to analyse guts of collected insects for source-specific compounds. Sugar sources often show distinct differences in their carbohydrate composition. This applies especially to honeydew, the excretion product of phloem-feeding ‘Sternorrhynchae’, which often features a broad range of phloem-feeder synthesized di- and oligosaccharides. 3. Out of these oligosaccharides, melezitose, has been widely used as an indicator of honeydew consumption. The use of melezitose or other honeydew saccharides as ‘signature sugars’ hinges on the assumption that the production of these sugars is unique to honeydew-secreting insects. 4. Here we show that the hymenopteran parasitoids Diadegma semiclausum and D. insulare synthesize the trisaccharides melezitose and erlose as well as the disaccharide maltose when fed sucrose, but not when feeding on an equimolar glucose–fructose mixture. 5. The presence of melezitose, erlose and maltose was confined to the parasitoid's digestive tract, indicating that enzyme activity is restricted to this area. D. semiclausum excrement contained low overall sugar concentrations and low relative levels of melezitose, erlose and maltose. 6. Possible functions of sugar synthesis in these nectar-feeding insects are discussed. [ABSTRACT FROM AUTHOR]

In response to herbivory by insects, several plant species have been shown to produce volatiles that attract the natural enemies of those herbivores. Using a Y-tube olfactometer, we investigated responses of the aphid parasitoid Diaeretiella rapae MacIntosh (Hymenoptera: Aphidiidae) to volatiles from Arabidopsis thaliana Columbia (Brassicaceae) plants that were either undamaged, infested by the peach-potato aphid, Myzus persicae Sulzer (Homoptera: Aphididae), or mechanically damaged, as well as to volatiles from just the aphid or its honeydew. In dual-choice experiments, female D. rapae given oviposition experience on A. thaliana infested with M. persicae were significantly attracted to volatiles from A. thaliana infested with M. persicae over volatiles from undamaged A. thaliana and similarly were significantly attracted to plants that had been previously infested by M. persicae, but from which the aphids were removed, over undamaged plants. Diaeretiella rapae did not respond to volatiles from M. persicae alone, their honeydew, or plants mechanically damaged with either a pin or scissors. We conclude that an interaction between the plant and the aphid induces A. thaliana to produce volatiles, which D. rapae can learn and respond to. Poor responses of D. rapae to volatiles from an A. thaliana plant that had two leaves infested with M. persicae, with the two infested leaves being removed before testing, suggested the possibility that, at this stage of infestation, the majority of volatile production induced by M. persicae may be localized to the infested tissues of the plant. We conclude that this tritrophic interaction is a suitable model system for future investigations of the biochemical pathways involved in the production of aphid-induced volatiles attractive to natural enemies. [ABSTRACT FROM AUTHOR]

In studies of foraging behaviour in a multitrophic context, the fourth trophic level has generally been ignored. We used four aphid hyperparasitoid species:Dendrocerus carpenteri(Curtis) (Hymenoptera: Megaspilidae),Asaphes suspensusWalker (Hymenoptera: Pteromalidae),Alloxysta victrix(Westwood) (Hymenoptera: Alloxystidae) andSyrphophagus aphidivorus(Mayr) (Hymenoptera: Encyrtidae), to correlate their response to different cues with their ecological attributes such as host range and host stage. In addition, we compared our results with studies of primary parasitoids on the same plant–herbivore system. First, the olfactory response of females was tested in a Y-tube olfactometer (single choice: plant, aphid, honeydew, parasitised aphid, aphid mummy, or virgin female parasitoid; dual choice: clean plant, plant with aphids, or plant–host complex). Second, their foraging behaviour was described on plants with different stimuli (honeydew, aphids, parasitised aphids, and aphid mummies). The results indicated that olfactory cues are probably not essential cues for hyperparasitoid females. In foraging behaviour on the plant, all species prolonged their total visit time and search time as compared to the control treatment (clean plant). OnlyA. victrixdid not react to the honeydew. Oviposition in mummies prolonged the total visit time because of the long handling time, but the effect of this behaviour on search time could not be determined. No clear correlation between foraging behaviour and host stage or host range was found. In contrast to specialised primary aphid parasitoids that have strong fixed responses to specific kairomones and herbivore-induced synomones, more generalist aphid hyperparasitoids seem to depend less on volatile olfactory stimuli, but show similarities with primary parasitoids in their use of contact cues while searching on a plant. [ABSTRACT FROM AUTHOR]

Host feeding is the consumption of host tissue by the adult female parasitoid. We studied the function of destructive host feeding and its advantage over non-destructive feeding on host-derived honeydew in the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae). We allowed parasitoids to oviposit until they attempted to host feed. We either prevented or allowed host feeding. Parasitoids had access to sucrose solution, with or without additional access to honeydew. Parasitoids that were allowed to host feed did not have a higher egg load 20 or 48 h after host feeding than parasitoids prevented from host feeding. Host feeding did not increase the number of eggs matured within these periods, nor did the time spent host feeding positively affect any of these response variables. On the other hand, the presence of honeydew did have a positive effect on egg load 20 and 48 h after host feeding compared with parasitoids deprived of honeydew. Parasitoids with access to honeydew matured more eggs within these periods than honeydew-deprived parasitoids. Host feeding increased life expectancy, but this effect was nullified when honeydew was supplied after the host-feeding attempt. In conclusion, feeding on honeydew could be an advantageous alternative to host feeding in terms of egg quantity and longevity. This applies especially to parasitoids exploiting Homoptera, because these parasitoids can obtain honeydew from the host itself. It is possible that destructive host feeding has evolved to enable females to sustain the production of high-quality anhydropic eggs, which may be important in the parasitoid's natural environment. We argue that future studies should take natural alternative food sources into more consideration. [ABSTRACT FROM AUTHOR]