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Highlights • Spiders are efficient predators in agroecosystems against pests. • Different non-prey foods significantly enhanced spiders' fitness. • Spiders actively selected the most beneficial non-prey foods. • Crops can offer alternative foods for spiders. • Agricultural management should promote practices that provide non-prey foods. Abstract Spiders are generalist predators adapted to consume a wide range of prey although their ability to exploit non-prey foods such as pollen, nectar, and honeydew has been referred but less studied. In this work, we investigated the effect of different non-prey food items (Glucose at 0.5 M; aphid honeydew; black scale honeydew; a mixture of glucose 0.5 M, phenylalanine 0.1 mM, proline 0.1 mM, and tryptophan 0.1 mM; honey at 10%, and pollen at 10%) on the survival of immature spiders of two functional groups represented by Haplodrassus rufipes (ground hunters) and Synema globosum (ambushers), and their feeding choices, in laboratory experiments. The overall survival of both species fed on non-prey foods significantly increased compared to individuals fed on water. The black-scale honeydew was the best food for H. rufipes increasing longevity up to 117 days. The highest survival reached by S. globosum was observed when fed on a mixture of glucose 0.5 M and three amino acids. When different non-prey food items were offered together, the exploring rate was significantly higher for H. rufipes than for S. globosum. H. rufipes chose to feed on honey whereas S. globosum chose the mixture treatment. The most chosen food items corresponded with those that provided the highest longevities in both species. Our results suggest that spiders could search, recognize and actively select the most beneficial non-prey food. Habitat management practices such as maintaining weed strips in the crop may provide these valuable supplementary food resources within agroecosystems contributing for biological pest control. [ABSTRACT FROM AUTHOR]

A modified method for enzymatically measuring concentrations of glucose, fructose and trehalose in parasitoid wasps is described and evaluated. The method has high specificity, gives results comparable to high performance liquid chromatography (HPLC), and shows good correlations with HPLC. The enzymatic method is quicker and less expensive than HPLC, and is safer, faster and more sensitive than another commonly used insect sugar determination method, the anthrone test. The method has potential to measure additional sugars, and details for measuring sucrose are provided as Supplementary material . We also investigate if endogenous enzymes can retain activity in insects preserved in ethanol, thus potentially skewing insect sugar measurements. The results show that the enzyme trehalase, which converts the insect haemolymph sugar trehalose to glucose, can remain active in insect specimens that are stored whole in ethanol. Thus, sugar measurements from insects preserved in this way have potential for bias towards low trehalose and high glucose. In contrast, the activity of endogenous trehalase in insects that are either frozen at −20 °C, or crushed in ethanol is either much reduced or eliminated. If, prior to sugar analysis, insects are to be stored in ethanol at temperatures above −20 °C, then we recommend they be crushed. [ABSTRACT FROM AUTHOR]

The predatory gall midge Aphidoletes aphidimyza , which is used for augmentative biological control of aphids in greenhouses, uses aphid honeydew as an energy source. Currently, Rhopalosiphum padi on barley plants and Melanaphis sacchari on sorghum plants are used as the banker plant systems for A. aphidimyza to control Aphis gossypii on eggplant in Japan. We analyzed the sugar components of the honeydew of these three species by HPLC. The major components of honeydew were sucrose, fructose, and melezitose for A. gossypii ; glucose and fructose for R. padi ; and glucose, fructose, and melezitose for M. sacchari . Maltose and trehalose were minor components of the honeydew of these species. We investigated the influence of sugars, including three artificial aphid honeydews, six sugar components, and distilled water, on the longevity of unmated A. aphidimyza . Both females and males attained the greatest longevity on sucrose and artificial honeydew of A. gossypii . Mean longevities of both females and males were shortest when they were provided only with water. We conducted another experiment in which a mated female was released in a cage with an eggplant seedling infested with A. gossypii and fed with sucrose or only water. Females fed with sucrose lived significantly longer and had higher lifetime fecundity than those fed only water. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aphytis melinus accepted and fed on five common citrus honeydews. [•] A. melinus fitness (measured as longevity and realized fecundity) entirely depended on the honeydew source. [•] A. melinus discriminated between honeydews with high and poor nutritional quality. [•] The presence of different honeydews in agroecosystems should be considered in biological control programs. [Copyright &y& Elsevier]

Highlights: [•] Aphid honeydew enhances adult hoverfly longevity. [•] When pollen and nectar are available, honeydew still generates additional survival. [•] Feeding on floral resources for only one week is sufficient for female reproduction. [•] This implies a reduced need to commute between feeding sites and oviposition sites. [•] Hoverfly larvae are able to suppress aphid colony growth. [ABSTRACT FROM AUTHOR]

Abstract: Sugars from extrafloral nectar and honeydew may be important resources for nocturnal cursorial spiders such as Cheiracanthium inclusum (Hentz) and Hibana futilis (Banks). C. inclusum spiderlings given only water survived an average of 6.1d. When provided with cotton extrafloral nectar and mealybug honeydew, their survivorship was extended to an average of 52.6 and 37.9d, respectively (870% and 626% increases). Choice tests demonstrated conclusively that spiders fed on nectar, honeydew and sugar solutions to obtain nutrients, and not simply to obtain moisture. Component sugars of extrafloral nectar (sucrose, glucose and fructose) and honeydews (maltose, melezitose and raffinose) were equally acceptable for feeding by H. futilis, but not for C. inclusum. Maltose was fed on by C. inclusum for significantly shorter periods than the other plant and honeydew sugars. Consumption of each of the individual sugars by H. futilis improved spiderling survival significantly over water, but less for raffinose than for the other sugars. The percent improvement in mean H. futilis survival over water alone varied from 394% for raffinose (mean=16.6d) to 1414% for maltose (mean=56.9d). The remaining four sugars extended survival greater than 1079%. That spiderlings survived for weeks on diets comprised only of individual sugars indicates that the availability of nectar and honeydew can be of considerable importance to the survivorship of cursorial spiders in the field. [Copyright &y& Elsevier]

Abstract: Protopulvinaria pyriformis (Cockerell) (Hemiptera: Coccidae), a scale native to South America, is a major pest of laurel, Laurus nobilis L., and a potential pest of other ornamental plants in urban green areas. We evaluated the potential of Metaphycus helvolus (Compere) (Hymenoptera: Encyrtidae), its major parasitoid, as a biological control agent against P. pyriformis. This parasitoid was imported from South Africa to control soft scales in Europe more than 20years ago. Three factors limited its efficacy: (i) the scale frequently thwart parasitoid attack by removing its stylet and wiggling, a unique defense in soft scales, (ii) scale honeydew extended M. helvolus lifespan little more than water, and (iii) P. pyriformis did not encapsulate Metaphycus spp. eggs but immature parasitoids died during their prepupal stage, which may have been caused by laurel plant secondary compounds from laurel. This parasitoid mortality had not been previously reported in immature parasitoids of genus Metaphycus. These three novel aspects should be considered when choosing a suitable parasitoid in future soft scale biological control programs. [Copyright &y& Elsevier]

Abstract: Ants frequently protect honeydew-excreting hemipterans from their natural enemies in exchange for food, and these interactions can have a negative impact on biological control. Invasive ant species, such as the Argentine ant, Linepithema humile (Mayr), enter into mutualisms with some hemipteran species and are generally regarded as more aggressive than native ants. Consequently, they may be more effective at protecting honeydew-producing hemipterans from natural enemy attack. We compared changes in populations of Aphis gossypii (Glover) tended by equal numbers of invasive L. humile, and the North America native Tapinoma sessile (Say), when exposed to the natural enemies Chrysoperla carnea (Stephens), Hippodamia convergens (Guer.) and Aphidius colemani (Viereck). While more L. humile than T. sessile workers foraged on plants with A. gossypii, both ants were equally effective at protecting A. gossypii from their natural enemies when aphid populations were relatively low. Using larger starting populations, A. gossypii were less negatively impacted by C. carnea or H. convergens when tended by L. humile than T. sessile. In a field experiment, the number of Aphis gossypii on plants with L. humile or T. sessile were greater than on plants without ants. We conclude that due to its higher foraging tempo L. humile may more effectively patrol plant surfaces supporting honeydew-producing hemipterans than T. sessile, which may, in part, underlie the success of this invasive ant. [ABSTRACT FROM AUTHOR]

Abstract: Augmentative biocontrol constitutes a safe option to reduce pest populations through the enhancement of natural enemies’ activity. In this context, the aphidophagous syrphid Episyrphus baltetaus (De Geer) (Diptera: Syrphidae) is a promising candidate for aphid biological control: larvae of this syrphid attack and consume a wide range of aphid species and are found on many vegetable crops. Because natural populations of beneficial insects are not always sufficient to regulate the pest infestations, this work has focused on the conception of a biological control device containing syrphid eggs which ones can easily be introduced in fields or greenhouses. Using semiochemicals [E-(β)-farnesene, R-(+)-limonene and (Z)-3-hexenol], honeydews and “artificial honeydews” (10% or 30% aqueous solutions of sucrose, fructose and glucose), the syrphid oviposition was artificially induced on an inert surface. Specifically, E-(β)-farnesene and concentrated mono-sugars (30%) were identified as the most efficient ovipositional stimulants. To test and validate the biological control device described above, laboratory and field experiments were performed: a plastic lamella covered with syrphid eggs was suspended on aphid infested plants in order to measure the efficiency of the device. The results obtained were promising since populations of 500 aphids were eliminated in 10 days when 15 syrphid eggs were introduced. The use of such a biological control device could certainly contribute to the biological control to reduce the aphid infestations. [ABSTRACT FROM AUTHOR]

Abstract: The potential impact of nectar availability for biological pest control is of increasing relevance due to the disappearance of non-crop plants in intensified agricultural landscapes. However, little is known about how floral resources and their spatial distribution in and around crop fields influence cereal aphid parasitoid (Hymenoptera, Aphidiidae) survival and population dynamics. Cereal aphid parasitoids may be less dependent on flowers as they can use honeydew from their aphid hosts as an alternative food resource. However, honeydew appears to be less suitable as a food source for parasitoids when compared to nectar. Here the effects of flower distribution (nectar), aphid abundance (honeydew quantity) and honeydew quality on parasitoid life history parameters were explored using a spatially explicit, individual-based simulation model. In addition, effects of the availability of floral resources in field margins on parasitism levels in winter wheat were investigated in a field study. In the simulation study three flower distributions were compared: (i) flowers restricted to the field margin (most common in agricultural landscapes) or (ii) flowers in strips within the crop, and (iii) random flower distribution in the field. Simulations suggest that nectar feeding increases parasitoid longevity and parasitism at low aphid densities, but only in fields with randomly distributed flowers. In contrast, the spatial distribution of flowers did not affect the parasitoid longevity and parasitism rate at high aphid densities, where parasitoid feeding was restricted to the abundant honeydew resources. In simulations, parasitoid survival and the number of aphids parasitized were also affected by the nutritional quality of the honeydew, with low quality honeydew having a less positive effect on parasitoid longevity and parasitism rate. The field study did not indicate evidence of a significant relationship between flower cover in field margins and parasitism rates in wheat near the margins. This finding is compatible with results from simulations and suggests that honeydew feeding is more prevalent in cereal aphid parasitoids than nectar feeding. In conclusion, nectar may be an important factor for the potential biocontrol success of cereal aphid parasitoids, but most likely only at low aphid densities and especially when flowers are broadly distributed in the field. [Copyright &y& Elsevier]

Abstract: The food available to coccinellid larvae and their exposure to predation is influenced by where they are placed as eggs. This review examines adult distribution and female oviposition strategies which in turn determine the distribution of coccinellid larvae in habitats. Immigration into a habitat can be influenced by visual and olfactory cues related to habitat quality. Adults are retained in a habitat if sufficient food resources are present. The abundance and quality of food in a habitat affects the reproductive output of a female and survival of larvae. Consequently, there is higher retention and oviposition preference for sites with abundant essential prey. Coccinellids also increase reproduction in response to non-prey foods (i.e., pollen), but avoid ovipositing in areas with copious amounts of honeydew. In laboratory studies, many plant-derived chemicals have been demonstrated to be attractants and oviposition stimulants. The need to place eggs in proximity to food for offspring must be weighed against the risk of cannibalism and intraguild predation. Lady beetles avoid egg predation by reducing oviposition where other adults are present, ovipositing on plants associated with less exposure or incidence of intraguild predation, and avoiding areas with tracks and frass of con- and heterospecific larvae. Indeed, deterrent cues for avoiding predation seem stronger than the positive ones associated with food. An understanding of the resources needed for successful reproduction and larval development in a habitat and the sensory cues that signal these resources, and thus elicit oviposition, may enhance our understanding of the underlying mechanisms affecting coccinellid distribution in habitats. [Copyright &y& Elsevier]

Abstract: The majority of predators and parasitoids require non-prey food as part of their diet. The availability of suitable non-prey food can impact predator–prey and parasitoid–host dynamics and may be critical to the efficacy of biological pest control. A growing body of work addresses the role of floral nectar in conservation biological control programs. In comparison, we know relatively little about the role of honeydew as a sugar source for predators and parasitoids, in spite of the fact that honeydew is often the predominant sugar source in agroecosystems. Here we test the hypothesis that honeydew is a less suitable food source when compared with other sugar sources, using data from parasitoid literature. We also explore whether parasitoids of honeydew-producing insects show particular adaptations allowing them to optimize the exploitation of this suboptimal food source. A review of available literature supports the general hypothesis that honeydew is inferior to other sugar sources, although there is considerable variation in the quality of honeydew depending on the honeydew producer and its host plant. The accrued dataset is not consistent with our second hypothesis that parasitoids of honeydew-producing hosts fare better on this nutritionally inferior food source as compared with parasitoid species which exploit hosts that do not produce honeydew. Finally we review evidence on the use of honeydew by predators and parasitoids under field conditions and explore implications for biological pest control programs. [Copyright &y& Elsevier]

Abstract: Conservation biological control (CBC) aims at improving the efficacy of natural enemies and can contribute to safer and more effective biological control practices. Considerable progress in this field has been made during recent years, and it is therefore justified to review key findings in a special issue of Biological Control. The following topics, with primary emphasis on CBC of arthropods by arthropods are covered in this issue: (1) honeydew as a food source for natural enemies, (2) artificial food sprays, (3) shelter habitats, (4) chemical ecology and CBC, (5) natural enemy diversity and CBC, (6) CBC at a landscape scale, (7) CBC as provider of multiple ecosystem services, and (8) economics and adoption of CBC. These reviews present substantial evidence that CBC can attract and/or improve the fitness of natural enemies. However, studies showing that this translates into decreased pest damage, increased crop yield or quality and improved economic profit for growers are still rare. We conclude that future researchers should investigate the effect of CBC at these levels, but also that we need a better understanding of which conditions CBC will reduce pest populations in the field. CBC has the potential to increase ecosystem services other than biological control and consideration of the economic benefits of this will increase the likelihood of adoption of CBC. [Copyright &y& Elsevier]

Abstract: The effect of five different food resources (Coccus hesperidum honeydew, honey-water, Lobularia maritima, Fagopyrum esculentum and water only) on the longevity, fecundity, and progeny fitness of female Gonatocerus ashmeadi, an egg parasitoid of the glassy-winged sharpshooter (Homalodisca vitripennis) was investigated in the laboratory. Female G. ashmeadi survived 208–405% longer (up to 11.7 days longer) when fed C. hesperidum honeydew, honey-water, L. maritima and F. esculentum compared with water only. Similarly, all food treatments resulted in up to 378% more progeny (up to 80 more total progeny) than those females provisioned with water only. Mean percentage female progeny ranged from 70 to 81% and did not significantly differ between food treatments. The highest daily fecundity (22–29 progeny) occurred on the first day of oviposition for each food treatment and generally declined as female G. ashmeadi aged. Females deposited 61–100% of offspring within the first 5 days, after which, daily fecundity usually declined to 0–6 offspring per day. For all experimental diets except L. maritima, the number of male progeny oviposited remained relatively constant over time (∼2 males per oviposition bout) but the proportion of males oviposited increased as female G. ashmeadi aged, as oviposition rates declined and fewer female eggs were subsequently laid. There was a strong positive correlation between hind tibia length (HTL) and total progeny produced by G. ashmeadi fed honey-water. There was no correlation between HTL and longevity of female G. ashmeadi fed honey-water. Mean HTL of G. ashmeadi progeny did not significantly differ between food treatments. Estimated progeny fecundity based on HTL, indicated that offspring produced by females provided with water only was 12–15 eggs or 9–12% lower than females that had access to food resources. This difference was not statistically significant. Female progeny that were oviposited by females 9–13 days of age with access to food resources were significantly larger and contained on average 14–17 more eggs than those female progeny resulting from eggs deposited by females 1–8 days of age. [Copyright &y& Elsevier]

Abstract: The effect of dietary supplements on the longevity of male and female Gonatocerus ashmeadi, G. triguttatus and G. fasciatus (Hymenoptera: Mymaridae), was determined in the laboratory. Treatments included: water only, 3:1 honey–water solution, floral and extra-floral nectars from five different plants (excised stems from Fagopyrum esculentum, Lobularia maritima, Phacelia tanacetifolia, Anethum graveolens and Vicia faba), honeydew from Coccus hesperidum and Homalodisca vitripennis (formally H. coagulata), a commercially available food supplement (Eliminade) and citrus foliage. Additionally, the sugar composition of each food resource was determined using HPLC and whole flower extracts. Honey–water and F. esculentum nectar significantly increased longevity of male and female G. ashmeadi, G. triguttatus, and G. fasciatus up to 1860%, 1323% and 1459%, respectively, when compared with water. For both sexes and all three parasitoid species, survival on citrus foliage, H. vitripennis excrement, and P. tanacetifolia flowers was equivalent to that on water only. The longevity of G. ashmeadi and G. triguttatus was up to 539% higher on Eliminade compared with water only, however there was no significant effect of Eliminade on survival of G. fasciatus. Coccus hesperidum honeydew increased survival times up to 665% for all mymarid species compared with citrus foliage alone. HPLC analysis indicated that food resources most beneficial to Gonatocerus parasitoids possessed a high proportion of glucose (up to 44%) and fructose (up to 53%), suggesting that sucrose may not be as important for parasitoid survival. Citrus and P. tanacetifolia flowers contained favorable proportions of glucose and fructose, but the inability of Gonatocerus spp. to benefit from this may be related to flower morphology which could prevent access to nectar. [Copyright &y& Elsevier]

Abstract: We examined the effects of cotton aphid honeydew and buckwheat floral nectar on the lifespan and body carbohydrate nutrient levels of the phorid fly, Pseudacteon tricuspis (Diptera: Phoridae). Compared to flies provided with water only, cotton aphid honeydew modestly but significantly increased longevity of female and male P. tricuspis by about 1 day, with significant increases in the body levels of fructose, total sugars, and glycogen. Age had a positive effect on the levels of total sugars and glycogen in honeydew-fed flies. However, sex and mating had no significant effect on longevity and body nutrient levels. Body size (as measured by wing length) was positively correlated with glycogen levels in males, with larger males accumulating more glycogen from honeydew than smaller males. P. tricuspis flies were observed foraging on buckwheat flowers. However, no significant effects of buckwheat nectar on phorid fly longevity and body nutrient levels were detected. These results may suggest that buckwheat florets are morphologically incompatible with the mouthparts of phorid flies, or the possibility of innate behavioral characteristics of phorid flies that limit nectivory. Alternatively, buckwheat nectar may be quantitatively or qualitatively inferior to cotton aphid honeydew or may contain compounds that are mildly repellent to P. tricuspis. Future studies will investigate the mechanisms behind the observed reduced suitability of buckwheat nectar as a food source for P. tricuspis. Conservation of naturally occurring sugar sources in the field, including exposed sugar sources such as honeydew, may promote P. tricuspis lifespan and possibly, its impact as a biological control agent against imported fire ants, Solenopsis spp. (Hymenoptera: Formicidae). [Copyright &y& Elsevier]

Aphidius ervi (Haliday) (Hymenoptera: Braconidae) is a solitary aphid endoparasitoid. Adults feed on honeydew and possibly on other sugar sources such as nectar. Sugar sources can vary qualitatively and quantitatively according to biotic factors and environmental conditions. Experiments were conducted to determine the influence of quantitative variations of sugar sources on survival, feeding behavior, and consumption of A. ervi. A 1:1 glucose–fructose mixture was tested in a range of concentrations (0–70% (w/v)). The lifetime of both sexes increased significantly with increasing sugar concentration. The optimal lifetime was achieved by insects fed with 50 and 70% (w/v) of sugar solution for males and 70% (w/v) for females. Behavioral studies showed that sugar concentrations had a significant influence on feeding duration: for males and females feeding duration increased with sugar concentration. Longevity primarily depended on the concentration of the sugar solution, rather than the quantity of sugar solution ingested. In the last experiment, we studied the effect of feeding intervals on the lifetime of A. ervi females. Females fed with a 50% (w/v) 1:1 glucose–fructose mixture continuously or twice a day lived eight times longer than unfed parasitoids. In contrast, females fed every two days lived only half as long as those fed daily. We can thus conclude that females need at least two food intakes per day to attain maximum longevity. Our results provide insight into the nutritional requirements of A. ervi under laboratory conditions. Such information can be a basis to improving the longevity of this biocontrol agent by sugar feeding in the field and in greenhouses. [Copyright &y& Elsevier]

[Display omitted] • We review how ants affect pest abundance, and their natural enemies on citrus crops. • Ants affect the non-honeydew producing pests, but favour the honeydew producers. • Ants affect pests with edaphic stages, but favour pests without such stages. • The identity of the most abundant ant species affect the natural enemies. • Ants affect the generalist and winged natural enemies of honeydew-producing pests. Ants are one of the most abundant insect groups in citrus orchards. They help in controlling pests, but they can also facilitate the outbreak of other pests, such as those that produce honeydew. Moreover, ants can also affect natural enemies of pests. Here, we review how ants affect pest abundance, considering whether the pest produces honeydew and whether it spends part of its life-cycle in the soil (edaphic stages). We also investigated the effects of the presence of ants on natural enemies with a meta-analysis and how this effect is modified by honeydew production by the pest, the most abundant ant species, and the specialization and mode of dispersal (winged or wingless) of the natural enemy. The presence of ants decreased the abundance of non-honeydew producing pests, but increased the abundance of honeydew producers. Ants increased the abundance of pests without edaphic stages, but decreased pests with such stages. In addition, the identity of the most abundant ant species affected the abundance of natural enemies; the ants Iridomyrmex rufoniger and Lasius grandis had a negative impact whereas other ant species did not affect the abundance of natural enemies. Moreover, the presence of ants decreased the abundance of generalist and winged natural enemies of honeydew-producing pests. Our review provides crucial information on the effects of ants on biological control practices in citrus orchards, and increases our understanding of the relationships between ants, pests and their natural enemies. [ABSTRACT FROM AUTHOR]