| 1. |
- Belivanov, Yordan K., et al.
(author)
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The time scale of isotope signals in spiders : molting the remains of a previous diet
- 2015
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 156:3, s. 271-278
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Journal article (peer-reviewed)abstract
- Stable isotope analysis (SIA) has emerged as an important tool for understanding consumer diets and diet shifts. However, although the general idea behind SIA is clear, the interpretation of data is often fraught with problems because tissue turnover and fractionations are not known. We investigated shifts in stable isotope composition of spiders following a diet shift, using mealworms fed either maize (C4) or wheat (C3) flour. Mealworms had different carbon isotope composition depending on their diet and this difference was reflected in spider body parts. In the experiment, we first fed the spiders on a diet of either maize-fed or wheat-fed mealworms and then switched diet at the time of the second molt. Spiders were then sampled repeatedly until the next molt. We sampled both legs and abdomens, as these are presumed to have different turnover of tissue, and also molt remains were sampled when this was relevant. The data indicated that the spider legs had a turnover of about 20days, whereas the spider abdomens had a turnover of about 8days. Molt remains had the slowest turnover and reflected the diet at the previous molt, when the exoskeleton was formed. Both these observations indicate that SIA may be successfully used for elucidating diet shifts. More problematic was the fact that fractionation of carbon isotope ratios varied with body parts and diets. When spiders were fed maize-mealworms then the fractionation was larger for abdomens, but when the spiders were fed wheat-mealworms then the fractionation was larger for legs. The mechanisms underlying this pattern are unclear and deserve further attention.
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| 2. |
- Echeveste, Iñaki
(author)
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Physiological development and dispersal ability of newly emerged Monochamus galloprovincialis
- 2016
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 161, s. 141-151
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Journal article (peer-reviewed)abstract
- Novel associations between exotic pathogens and native insects may result in major ecological and economical losses. In Europe, Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae) is the only known vector of the exotic pine wood nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle (Nematoda: Aphelenchoididae), the causal agent of pine wilt disease (PWD). Transportation of goods containing nematode-infested beetles is the main pathway for the spread of the disease. In this scenario, management actions involving early detection and eradication are critical to stop further spread by the vector. Although dispersal of mature M.galloprovincialis has been successfully tracked using commercial baits and traps, dispersal ability of immature individuals is poorly understood. Sexual maturation and other physiological traits related to dispersal were studied for newly emerged M.galloprovincialis after different shoot-feeding spans. Sexual maturation was complete after on average 12 (males) or 13 (females) feeding days. Monochamus galloprovincialis adults emerged with an average of 10% lipid and 23.8% (males) or 29.9% (females) pterothorax muscle content, and these percentages did not change significantly during shoot feeding. Microtomography images of wing muscle structures at different maturation stages confirmed these results. Emerged adults that were kept unfed survived an average of 12days in the lab. The ability of unfed immature insects to fly through hostless terrain was studied by marking and releasing newly emerged insects from a crop area located up to 3km away from two small pine stands. The longest flown distance recorded was 2km. Fitted regressions indicated that immature insects could have travelled up to 3109m to reach the experimental stands. We found that M.galloprovincialis emerge with well-developed thoracic muscles and energy reserves that enable them to sustain long flights over non-forested areas. These findings should aid managers and policy makers in devising sound procedures in areas where the risk of introducing PWD is high.
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| 3. |
- Fedderwitz, Frauke, et al.
(author)
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The structure of feeding behavior in a phytophagous insect (Hylobius abietis)
- 2015
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In: Entomologia Experimentalis et Applicata. - 0013-8703 .- 1570-7458. ; 155, s. 229-239
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Journal article (peer-reviewed)abstract
- Analysis of the feeding behavior of animals using such a high temporal resolution that meals can be defined may improve our understanding of the mechanisms regulating feeding. Meals can be distinguished in an ethologically meaningful manner by using the ‘meal criterion’, the shortest non-feeding interval between feeding bouts recognized as meals. However, such a criterion has only been determined for a few insect species. Applying a recent method developed for assessing meal criteria for vertebrates, we determined the meal criterion for Hylobius abietis (L.) (Coleoptera: Curculionidae) based on data from video recordings of single individuals feeding on seedlings of Norway spruce, Picea abies (L.) Karst. (Pinaceae). The pine weevil is an economically important pest insect because it feeds on the stem bark of planted conifer seedlings. Weevils had 4-5 meals per day. Each meal lasted about 24 min during which about 13 mm2 of bark per meal were removed. Females had longer total meal durations and longer non-feeding intervals within meals than males. Girdling seedlings did not affect the weevils’ feeding properties. The size of meals was significantly correlated to the duration of non-feeding intervals before and after them. This study is one of few describing the feeding behavior of an insect at a temporal resolution that allows individual meals to be distinguished. With more meal-related data from insects available, differences in meal properties may be interpreted based on phylogeny, ecology, and physiology. Our results may also assist in the setup and interpretation of studies of plant-insect interactions, and facilitate the evaluation and development of methods to protect plants against herbivores.
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| 4. |
- Friberg, Magne, et al.
(author)
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Butterflies and plants : preference/performance studies in relation to plant size and the use of intact plants vs. cuttings
- 2016
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 160:3, s. 201-208
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Journal article (peer-reviewed)abstract
- Plants have evolved a number of defences to ameliorate herbivore attacks including chemicals induced by mechanical wounding. Such changes in plant chemical composition are potential confounding factors in experiments on plant-insect interactions, which often present cuttings of potential host plants to phytophagous insects. In particular, this could affect studies of female egg-laying preference and larval performance, because the same plant chemicals that deter certain generalist insects can elevate attacks from more specialized insects. Furthermore, plant cuttings are by definition smaller than intact plants, and any female host size preference could thus affect experiments using plant cuttings. We first assessed female preference and larval performance of a specialist herbivore, Pieris napi (L.) (Lepidoptera: Pieridae, Pierini), confronted with either intact plants or leaf-cuttings of four Brassicaceae host plants, Alliaria petiolata (Bieb.) Cavara & Grande, Barbarea vulgaris (L.) WT Aiton, Berteroa incana (L.) DC., and Brassica napus (L.). Egg and larval survival did not differ between intact plants and leaf-cuttings, whereas larval growth was slightly, but significantly, faster on leaf-cuttings. Females, however, significantly preferred to lay eggs on intact plants of all four hosts, although the preference hierarchy for the intact plants was largely mirrored by that for leaf-cuttings. We then tested the female preference for different size-classes of intact B. napus plants. Small individuals received more eggs than larger individuals, and follow-up experiments showed that this difference was largely generated by a strong female preference for cotyledon leaves; there was no significant difference in female preference for large and small individuals when both carried cotyledons, and females landing on cotyledons were more likely to oviposit compared to when landing on a true leaf. Our study concludes that plant cuttings can serve as adequate proxies for live plants for preference/performance studies, but that experimentalists should be aware of the variation imposed both by plant handling and plant phenology for female oviposition preference.
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| 5. |
- Glinwood, Robert, et al.
(author)
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Olfactory responses of Rhopalosiphum padi to three maize, potato, and wheat cultivars and the selection of prospective crop border plants
- 2015
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 157, s. 241-253
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Journal article (peer-reviewed)abstract
- Understanding host plant volatile -aphid interactions can facilitate the selection of crop border plants as a strategy to reduce plant virus incidence in crops. Crop border plant species with attractive odours could be used to attract aphids into the border crop and away from the main crop. As different cultivars of the same crop can vary in their olfactory attractiveness to aphids, selecting an attractive cultivar as a border crop is important to increase aphid landing rates. This study evaluated olfactory responses of the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), to three cultivars each of maize [Zea mays L. (Poaceae)], potato [Solanum tuberosum L. (Solanaceae)], and wheat [Triticumaestivum L. (Poaceae)] with the aim of selecting an attractive crop border plant to reduce the incidence of the non-persistent Potato virus Y [PVY (Potyviridae)] in seed potatoes. Volatiles emitted by the crop cultivars were collected and identified using coupled gas chromatography/mass spectrometry. Quantitative and qualitative differences were found among cultivars. Behavioural responses of alate R. padi to odours of the cultivars and synthetic compounds identified from the plants were determined with a four-arm olfactometer. Rhopalosiphum padi was attracted to odours emitted from maize cultivar 6Q-121, but did not respond to odours from the remaining eight crop cultivars. Volatile compounds from maize and wheat cultivars that elicited a behavioural response from R. padi and contributed to differences in plant volatile profiles included (Z)-3-hexenyl acetate (attractant) and a-farnesene, (E)-2-hexenal, indole, and (3E,7E)-4,8, 12-trimethyltrideca-1,3,7,11-tetraene (TMTT) (repellents). We conclude that maize cv. 6Q-121 is potentially suitable as a crop border plant based on the behavioural response of R. padi to the olfactory cues emitted by this cultivar. The findings provide insight into selecting crop cultivars capable of attracting R. padi to crop border plants.
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| 6. |
- Jakobsson, Johan, et al.
(author)
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Antennal and behavioural responses of the spruce seedmoth, Cydia strobilella, to floral volatiles of Norwayspruce, Picea abies, and temporal variation in emissionof active compounds
- 2016
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 1570-7458 .- 0013-8703. ; 160:3, s. 209-218
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Journal article (peer-reviewed)abstract
- We investigated whether spruce seed moth, Cydia strobilella L. (Lepidoptera: Tortricidae, Grapholitini), one of the most damaging seed predators on Norway spruce, Picea abies (L.) H. Karst (Pinaceae), uses olfactory cues during host search. Analyses with coupled gas chromatography and electroantennography revealed that antennae of both sexes of moths responded consistently to three compounds in the headspace from female spruce flowers, i.e., α-pinene, β-pinene, and myrcene, but not to limonene as has been previously reported for this species. The amounts of these active volatiles released from flowers and cones of P. abies were quantified, and their diurnal and seasonal variation was monitored. The total release of the active volatiles correlated well with the diurnal and seasonal flight activity of C. strobilella as revealed by catches of males in pheromone-baited traps. In field trapping experiments, where baits were loaded with proportions and enantiomeric ratios of α-pinene, β-pinene, and myrcene matching those of the female P. abies floral headspace, substantial catches of male C. strobilella were achieved, whereas few females were captured. These surprising results suggest that male C. strobilella make use of host volatiles to aid them in their search for females.
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| 7. |
- Karlsson, Miriam Frida
(author)
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Host species and vegetable fruit suitability and preference by the parasitoid wasp Fopius arisanus
- 2017
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In: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 163, s. 70-81
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Journal article (peer-reviewed)abstract
- Parasitoids that oviposit in a concealed host inside a plant part need to be able to find both the plant and the host. Egg parasitoids of fruit-infesting Tephritidae need to assess the oviposition site based both on the host egg and the infested fruit. Infestation by Tephritidae fruit flies threatens fruit and vegetable production. Management methods have been implemented including biological control, using Fopius arisanus Sonan (Hymenoptera: Braconidae). The parasitism by F. arisanus in three Tephritidae flies in vegetable fruits was investigated. Laboratory assays were conducted to assess the parasitoid's preference and survival. Zucchini, sweet pepper, and tomato were artificially infested with eggs of Bactrocera dorsalisHendel, Ceratitis capitata Wiedemann, and Ceratitis cosyraWalker (all Diptera: Tephritidae), then exposed tomated naive F. arisanus females in a 20: 1 egg: parasitoid ratio. Parasitoid behavioral activities (resting, antennating, probing, ovipositing) were observed on the infested fruits. Parasitism rate was determined by dissection of fruit fly eggs under a stereomicroscope. Behavioral activities of F. arisanus differed between all the fruits when infested with B. dorsalis or C. cosyra eggs but differed only between some of the fruits when infested with C. capitata. Fopius arisanus preferred B. dorsalis over C. capitata and C. cosyra, with a parasitism rate 29 higher on B. dorsalis compared to the Ceratitis species. Preference for fruits was dependent on the infesting fruit fly. The emergence of F. arisanus was higher with B. dorsalis than with Ceratitis spp. Although B. dorsalis completed its development earlier than Ceratitis spp., host fly species did not affect the developmental time of F. arisanus. We discuss the significance of F. arisanus preference in relation to naturally occurring Tephritidae infestations. We also discuss whether some fruits might constitute a refuge for Tephritidae flies and whether this will affect the current biological control efforts against B. dorsalis.
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| 8. |
- Kehl, Tobias, et al.
(author)
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Fat and sassy : factors underlying male mating success in a butterfly
- 2015
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In: Entomologia Experimentalis et Applicata. - : The Netherlands Entomological Society. - 0013-8703 .- 1570-7458. ; 155:3, s. 257-265
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Journal article (peer-reviewed)abstract
- Theory predicts that male mating success depends on resource holding potential (RHP), which is reflected by proxies of condition, such as body mass, fat content, strength, or weaponry. In species lacking any physical means to inflict injuries upon combatants, such as butterflies, the factors determining mating success are less clear. Against this background, we explored the determinants of male mating success in the tropical butterfly Bicyclus anynana Butler (Lepidoptera: Nymphalidae: Satyrinae), by comparing physiological, immunological, and morphological traits between winning and losing males. Our results showed that successful males are characterized by a better flight performance, evidenced by having longer wings, a heavier thorax, a lighter abdomen, a higher fat content, and higher phenoloxidase expression levels than their unsuccessful counterparts, when being compared after their first mating. Males that won three consecutive trials against the same combatant were also characterized by a better flight performance, having larger forewings, a higher body mass, and a higher fat content. Thus, successful males were larger and in better condition than unsuccessful ones. Strikingly, many differences found indicated an enhanced flight performance for the former, which we suggest ultimately plays the key role for male mating success in B. anynana. As fat is the main energy source for flying insects, being crucial to flight endurance and in turn presumably to male mating success, it may represent a key determinant at the proximate level.
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| 9. |
- Mozuraitis, Raimondas, et al.
(author)
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Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c-album females, but do not stimulate oviposition
- 2016
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In: Entomologia Experimentalis et Applicata. - : Blackwell Publishing. - 0013-8703 .- 1570-7458. ; 158:3, s. 275-283
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Journal article (peer-reviewed)abstract
- The role of olfactory cues for host search is much less investigated in day-active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host-plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg-laying behavior of gravid Polygonia c-album L. (Lepidoptera: Nymphalidae) females. Eighty-nine volatile compounds were detected in a non-concentrated methanol extract of hop by gas chromatography-mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG-active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups - consisting of (1) hexanal, (E)-2-hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol - obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves.
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| 10. |
- Stenberg, Johan A, et al.
(author)
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Raspberry inflicts associational susceptibility to meadowsweet in a complex food web
- 2015
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In: Entomologia Experimentalis et Applicata. - : Wiley-Blackwell. - 0013-8703 .- 1570-7458. ; 157:1, s. 68-73
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Journal article (peer-reviewed)abstract
- Meadowsweet [Filipendula ulmaria (L.) Maxim. (Rosaceae)] has previously been reported to enjoy associational resistance in mixed populations with purple loosestrife [Lythrum salicaria L. (Lythraceae)] due to a shared hymenopteran parasitoid that provides top-down control of herbivory. Here, we report that meadowsweet suffers associational susceptibility in mixed populations with raspberry [Rubus idaeus L. (Rosaceae)] due to a shared herbivore, the raspberry flea beetle [Batophila rubi (Paykull) (Coleoptera: Chrysomelidae)]. Close to raspberry (less than 0.5 m), herbivory on meadowsweet often reached 20-25%, whereas further away (1.5-2 m) herbivory was almost always 0%. We especially highlight the different scales at which the opposing associational effects occur. The shared parasitoid forages throughout entire populations, making the level of population the focal scale of the associational resistance. The shared herbivore, however, spills over from raspberry to neighboring meadowsweets only, making the distance to individual raspberry plants the focal scale for associational susceptibility for meadowsweet. We conclude that different co-occurring plant species can mediate opposing associational effects on a focal host plant by altering the abundance and composition of herbivores and parasitoids, respectively, resulting in multiple selection layers to the geographic mosaic of herbivory.
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