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Insects, Volume 5, Issue 2 (June 2014), Pages 301-498

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Research

Jump to: Review

Open AccessArticle Effects of Invasive Winter Moth Defoliation on Tree Radial Growth in Eastern Massachusetts, USA
Insects 2014, 5(2), 301-318; doi:10.3390/insects5020301
Received: 20 January 2014 / Revised: 12 March 2014 / Accepted: 20 March 2014 / Published: 9 April 2014
Cited by 2 | PDF Full-text (617 KB) | HTML Full-text | XML Full-text
Abstract
Winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), has been defoliating hardwood trees in eastern Massachusetts since the 1990s. Native to Europe, winter moth has also been detected in Rhode Island, Connecticut, eastern Long Island (NY), New Hampshire, and Maine. Individual tree impacts [...] Read more.
Winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), has been defoliating hardwood trees in eastern Massachusetts since the 1990s. Native to Europe, winter moth has also been detected in Rhode Island, Connecticut, eastern Long Island (NY), New Hampshire, and Maine. Individual tree impacts of winter moth defoliation in New England are currently unknown. Using dendroecological techniques, this study related annual radial growth of individual host (Quercus spp. and Acer spp.) trees to detailed defoliation estimates. Winter moth defoliation was associated with up to a 47% reduction in annual radial growth of Quercus trees. Latewood production of Quercus was reduced by up to 67% in the same year as defoliation, while earlywood production was reduced by up to 24% in the year following defoliation. Winter moth defoliation was not a strong predictor of radial growth in Acer species. This study is the first to document impacts of novel invasions of winter moth into New England. Full article
Open AccessArticle Rhagoletis cerasi: Oviposition Reduction Effects of Oil Products
Insects 2014, 5(2), 319-331; doi:10.3390/insects5020319
Received: 24 December 2013 / Revised: 9 April 2014 / Accepted: 10 April 2014 / Published: 16 April 2014
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Abstract
The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is a highly destructive pest. Methods to control it are limited and alternatives are needed. Observations of cherry fruit flies suggest that females exert much effort to penetrate cherries at color change [...] Read more.
The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is a highly destructive pest. Methods to control it are limited and alternatives are needed. Observations of cherry fruit flies suggest that females exert much effort to penetrate cherries at color change stage (from green to yellow) for oviposition. Therefore, the question arose as to whether a physical barrier on the fruit surface could reduce oviposition. The effects of different commercial horticultural oil products on R. cerasi oviposition were evaluated in a series of laboratory, semi-field and field experiments. In the laboratory experiments, the rate of successful oviposition on fruits treated with 0.25% v/v of the rapeseed oil product Telmion was significantly reduced by 90% compared to the untreated control. In semi-field experiments, deposits of 1% of rapeseed, mineral and paraffinic oil significantly reduced oviposition for up to 3 days. Semi-field experiments indicated that the oil products lose efficacy within 3 to 6 days after application due to degradation. Although treatments with the rapeseed oil product Telmion reduced infestation rates in an on-farm field experiment, the infested fruit clearly exceeded the level of market tolerance of 2%. Further research is needed to assess whether combinations of oil products, higher application rates and different formulations might improve field efficacy. Full article
Open AccessArticle Twenty Years of Elfin Enumeration: Abundance Patterns of Five Species of Callophrys (Lycaenidae) in Central Wisconsin, USA
Insects 2014, 5(2), 332-350; doi:10.3390/insects5020332
Received: 24 February 2014 / Revised: 14 April 2014 / Accepted: 15 April 2014 / Published: 23 April 2014
Cited by 1 | PDF Full-text (320 KB) | HTML Full-text | XML Full-text
Abstract
We recorded five species of elfins (Callophrys) during annual spring surveys targeting frosted elfin C. irus (state-listed as threatened) in 19 pine-oak barrens in central Wisconsin USA during 1994–2013. At the northwest end of its range here, C. irus co-varied [...] Read more.
We recorded five species of elfins (Callophrys) during annual spring surveys targeting frosted elfin C. irus (state-listed as threatened) in 19 pine-oak barrens in central Wisconsin USA during 1994–2013. At the northwest end of its range here, C. irus co-varied with spring temperature, but declined significantly over time (eight sites verified extant of originally 17). Two other specialists increased significantly. The northern specialist, hoary elfin C. polios (nine sites), correlated positively with the previous year’s growing season precipitation. The southern specialist, Henry’s elfin C. henrici (11 sites), co-varied with winter precipitation and spring temperature and dryness. The two resident generalists had stable trends. For all species, the first observed date per year became earlier over time and varied more than the last observed date. Thus, flight period span increased with earlier first observed dates. Elfin abundance increased significantly with earlier first observed dates in the current and/or prior year. Three species (C. irus, C. henrici, a generalist) had more positive population trends in reserves than non-reserves. This suggests that C. irus declines correspond to habitat conditions. Thus, monitoring programs and habitat management specifically for C. irus appear necessary to obtain a long-term stable trend for this species in Wisconsin. Full article
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Open AccessArticle Glycolytic Activities in the Larval Digestive Tract of Trypoxylus dichotomus (Coleoptera: Scarabaeidae)
Insects 2014, 5(2), 351-363; doi:10.3390/insects5020351
Received: 3 March 2014 / Revised: 17 April 2014 / Accepted: 24 April 2014 / Published: 5 May 2014
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Abstract
The larvae of the Japanese horned beetle, Trypoxylus dichotomus (Coleoptera: Scarabaeidae: Dynastinae), are an example of a saprophage insect. Generally, Scarabaeid larvae, such as T. dichotomus, eat dead plant matter that has been broken down by fungi, such as Basidiomycota. It [...] Read more.
The larvae of the Japanese horned beetle, Trypoxylus dichotomus (Coleoptera: Scarabaeidae: Dynastinae), are an example of a saprophage insect. Generally, Scarabaeid larvae, such as T. dichotomus, eat dead plant matter that has been broken down by fungi, such as Basidiomycota. It is thought that β-1,3-glucan, a constituent polysaccharide in microbes, is abundant in decayed plant matter. Studies of the degradation mechanism of β-1,3-glucan under these circumstances are lacking. In the current study, we sought to clarify the relationship between the capacity to degrade polysaccharides and the food habits of the larvae. The total activities and optimum pH levels of several polysaccharide-degrading enzymes from the larvae were investigated. The foregut, midgut and hindgut of final instar larvae were used. Enzymatic activities were detected against five polysaccharides (soluble starch, β-1,4-xylan, β-1,3-glucan, pectin and carboxymethyl cellulose) and four glycosides (p-nitrophenyl (PNP)-β-N-acetylglucosaminide, PNP-β-mannoside, PNP-β-glucoside and PNP-β-xyloside). Our results indicate that the digestive tract of the larvae is equipped with a full enzymatic system for degrading β-1,3-glucan and β-1,4-xylan to monomers. This finding elucidates the role of the polysaccharide-digesting enzymes in the larvae, and it is suggested that the larvae use these enzymes to enact their decomposition ability in the forest environment. Full article
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Open AccessArticle Biomechanical Properties of Hemlocks: A Novel Approach to Evaluating Physical Barriers of the Plant–Insect Interface and Resistance to a Phloem-Feeding Herbivore
Insects 2014, 5(2), 364-376; doi:10.3390/insects5020364
Received: 19 March 2014 / Revised: 6 May 2014 / Accepted: 20 May 2014 / Published: 3 June 2014
Cited by 1 | PDF Full-text (274 KB) | HTML Full-text | XML Full-text
Abstract
Micromechanical properties that help mediate herbivore access may be particularly important when considering herbivorous insects that feed with piercing-sucking stylets. We used microindentation to quantify the micromechanical properties of hemlock, Tsuga spp., to quantify the hardness of the feeding site of the [...] Read more.
Micromechanical properties that help mediate herbivore access may be particularly important when considering herbivorous insects that feed with piercing-sucking stylets. We used microindentation to quantify the micromechanical properties of hemlock, Tsuga spp., to quantify the hardness of the feeding site of the invasive hemlock woolly adelgid, Adelges tsugae. We measured hardness of the hemlock leaf cushion, the stylet insertion point of the adelgid, across four seasons in a 1 y period for four hemlock species growing in a common garden, including eastern, western, mountain, and northern Japanese hemlocks. Leaf cushion hardness was highest in the fall and winter and lowest in summer for all species. Northern Japanese hemlock had relatively greater hardness than the remaining species. Our data contributes an additional perspective to the existing framework within which greater susceptibility and subsequent mortality of eastern hemlocks is observed. The potential application of microindentation to understanding the nature and relevance of plant mechanical defenses in plant–herbivore interactions is also demonstrated and highlighted. Full article
(This article belongs to the Special Issue Insect-Plant Interactions)
Open AccessArticle Contrasting Effects of Histone Deacetylase Inhibitors on Reward and Aversive Olfactory Memories in the Honey Bee
Insects 2014, 5(2), 377-398; doi:10.3390/insects5020377
Received: 31 October 2013 / Revised: 12 April 2014 / Accepted: 19 May 2014 / Published: 10 June 2014
Cited by 5 | PDF Full-text (736 KB) | HTML Full-text | XML Full-text
Abstract
Much of what we have learnt from rodent models about the essential role of epigenetic processes in brain plasticity has made use of aversive learning, yet the role of histone acetylation in aversive memory in the honey bee, a popular invertebrate model [...] Read more.
Much of what we have learnt from rodent models about the essential role of epigenetic processes in brain plasticity has made use of aversive learning, yet the role of histone acetylation in aversive memory in the honey bee, a popular invertebrate model for both memory and epigenetics, was previously unknown. We examined the effects of histone deacetylase (HDAC) inhibition on both aversive and reward olfactory associative learning in a discrimination proboscis extension reflex (PER) assay. We report that treatment with the HDAC inhibitors APHA compound 8 (C8), phenylbutyrate (PB) or sodium butyrate (NaB) impaired discrimination memory due to impairment of aversive memory in a dose-dependent manner, while simultaneously having no effect on reward memory. Treatment with C8 1 h before training, 1 h after training or 1 h before testing, impaired aversive but not reward memory at test. C8 treatment 1 h before training also improved aversive but not reward learning during training. PB treatment only impaired aversive memory at test when administered 1 h after training, suggesting an effect on memory consolidation specifically. Specific impairment of aversive memory (but not reward memory) by HDAC inhibiting compounds was robust, reproducible, occurred following treatment with three drugs targeting the same mechanism, and is likely to be genuinely due to alterations to memory as sucrose sensitivity and locomotion were unaffected by HDAC inhibitor treatment. This pharmacological dissection of memory highlights the involvement of histone acetylation in aversive memory in the honey bee, and expands our knowledge of epigenetic control of neural plasticity in invertebrates. Full article
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Open AccessArticle Female Moth Calling and Flight Behavior Are Altered Hours Following Pheromone Autodetection: Possible Implications for Practical Management with Mating Disruption
Insects 2014, 5(2), 459-473; doi:10.3390/insects5020459
Received: 27 March 2014 / Revised: 20 May 2014 / Accepted: 23 May 2014 / Published: 19 June 2014
Cited by 6 | PDF Full-text (225 KB) | HTML Full-text | XML Full-text
Abstract
Female moths are known to detect their own sex pheromone—a phenomenon called “autodetection”. Autodetection has various effects on female moth behavior, including altering natural circadian rhythm of calling behavior, inducing flight, and in some cases causing aggregations of conspecifics. A proposed hypothesis [...] Read more.
Female moths are known to detect their own sex pheromone—a phenomenon called “autodetection”. Autodetection has various effects on female moth behavior, including altering natural circadian rhythm of calling behavior, inducing flight, and in some cases causing aggregations of conspecifics. A proposed hypothesis for the possible evolutionary benefits of autodetection is its possible role as a spacing mechanism to reduce female-female competition. Here, we explore autodetection in two species of tortricids (Grapholita molesta (Busck) and Choristoneura rosaceana (Harris)). We find that females of both species not only “autodetect,” but that learning (change in behavior following experience) occurs, which affects behavior for at least 24 hours after pheromone pre-exposure. Specifically, female calling in both species is advanced at least 24 hours, but not 5 days, following pheromone pre-exposure. Also, the propensity of female moths to initiate flight and the duration of flights, as quantified by a laboratory flight mill, were advanced in pre-exposed females as compared with controls. Pheromone pre-exposure did not affect the proportion of mated moths when they were confined with males in small enclosures over 24 hours in laboratory assays. We discuss the possible implications of these results with respect to management of these known pest species with the use of pheromone-based mating disruption. Full article
(This article belongs to the Special Issue Pheromones and Insect Behaviour)
Open AccessArticle Pyrazines Attract Catocheilus Thynnine Wasps
Insects 2014, 5(2), 474-487; doi:10.3390/insects5020474
Received: 28 March 2014 / Revised: 10 June 2014 / Accepted: 16 June 2014 / Published: 19 June 2014
Cited by 4 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
Five previously identified semiochemicals from the sexually deceptive Western Australian hammer orchid Drakaea livida, all showing electrophysiological activity in gas chromatography–electroantennogram detection (EAD) studies, were tested in field bioassays as attractants for a Catocheilus thynnine wasp. Two of these compounds, (3,5,6-trimethylpyrazin-2-yl)methyl [...] Read more.
Five previously identified semiochemicals from the sexually deceptive Western Australian hammer orchid Drakaea livida, all showing electrophysiological activity in gas chromatography–electroantennogram detection (EAD) studies, were tested in field bioassays as attractants for a Catocheilus thynnine wasp. Two of these compounds, (3,5,6-trimethylpyrazin-2-yl)methyl 3-methylbutanoate and 2-(3-methylbutyl)-3,5,6-trimethylpyrazine, were attractive to male wasps. Additionally, the semiochemical 3-(3-methylbutyl)-2,5-dimethylpyrazine, a close analogue to 2-(3-methylbutyl)-3,5,6-trimethylpyrazine, identified in five other species of thynnine wasps, was equally active. The three remaining compounds from D. livida, which were EAD-active against Catocheilus, did not attract the insects in field trials. It is interesting that two structurally similar compounds induce similar behaviours in field experiments, yet only one of these compounds is present in the orchid flower. Our findings suggest the possibility that despite the high specificity normally characterising sex pheromone systems, the evolution of sexual deception may not be entirely constrained by the need to precisely match the sex pheromone constituents and blends. Such evolutionary flexibility may be particularly important during the early stages of speciation. Full article
(This article belongs to the Special Issue Pheromones and Insect Behaviour)
Open AccessArticle Preliminary Screening of Potential Control Products against Drosophila suzukii
Insects 2014, 5(2), 488-498; doi:10.3390/insects5020488
Received: 1 May 2014 / Revised: 3 June 2014 / Accepted: 14 June 2014 / Published: 20 June 2014
Cited by 5 | PDF Full-text (793 KB) | HTML Full-text | XML Full-text
Abstract
The first recording of Drosophila suzukii in the UK occurred in the south of England during August 2012. Since then sticky traps have continued to record the presence of individuals. Several products (both chemical and biological) were investigated for their efficacy against [...] Read more.
The first recording of Drosophila suzukii in the UK occurred in the south of England during August 2012. Since then sticky traps have continued to record the presence of individuals. Several products (both chemical and biological) were investigated for their efficacy against different life-stages of the pest. Both direct and indirect exposure to control products was assessed. Spinosad, chlorantraniliprole and the experimental product, TA2674, showed excellent potential as control agents when used as either a pre- or post-dipping treatment for blueberries with mortalities of 100%, 93% and 98% mortality, respectively, being achieved following pre-treatment. Direct spray application of all products tested had limited impact upon adult flies. Highest mortality (68%) was achieved following direct application of TA2674. Entomopathogenic agents (nematodes and fungi) tested appeared to reduce fly population development (ranges of 34–44% mortality obtained) but would seem unable to eradicate outbreaks. The potential of the tested products to control D. suzukii is discussed. Full article
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Review

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Open AccessReview Responses to Pheromones in a Complex Odor World: Sensory Processing and Behavior
Insects 2014, 5(2), 399-422; doi:10.3390/insects5020399
Received: 28 March 2014 / Revised: 21 May 2014 / Accepted: 22 May 2014 / Published: 17 June 2014
Cited by 5 | PDF Full-text (1582 KB) | HTML Full-text | XML Full-text
Abstract
Insects communicating with pheromones, be it sex- or aggregation pheromones, are confronted with an olfactory environment rich in a diversity of volatile organic compounds of which plants are the main releaser. Certain of these volatiles can represent behaviorally relevant information, such as [...] Read more.
Insects communicating with pheromones, be it sex- or aggregation pheromones, are confronted with an olfactory environment rich in a diversity of volatile organic compounds of which plants are the main releaser. Certain of these volatiles can represent behaviorally relevant information, such as indications about host- or non-host plants; others will provide essentially a rich odor background out of which the behaviorally relevant information needs to be extracted. In an attempt to disentangle mechanisms of pheromone communication in a rich olfactory environment, which might underlie interactions between intraspecific signals and a background, we will summarize recent literature on pheromone/plant volatile interactions. Starting from molecular mechanisms, describing the peripheral detection and central nervous integration of pheromone-plant volatile mixtures, we will end with behavioral output in response to such mixtures and its plasticity. Full article
(This article belongs to the Special Issue Pheromones and Insect Behaviour)
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Open AccessReview The Role of Sexual Selection in the Evolution of Chemical Signals in Insects
Insects 2014, 5(2), 423-438; doi:10.3390/insects5020423
Received: 8 April 2014 / Revised: 16 May 2014 / Accepted: 20 May 2014 / Published: 18 June 2014
Cited by 6 | PDF Full-text (139 KB) | HTML Full-text | XML Full-text
Abstract
Chemical communication is the most ancient and widespread form of communication. Yet we are only beginning to grasp the complexity of chemical signals and the role they play in sexual selection. Focusing on insects, we review here the recent progress in the [...] Read more.
Chemical communication is the most ancient and widespread form of communication. Yet we are only beginning to grasp the complexity of chemical signals and the role they play in sexual selection. Focusing on insects, we review here the recent progress in the field of olfactory-based sexual selection. We will show that there is mounting empirical evidence that sexual selection affects the evolution of chemical traits, but form and strength of selection differ between species. Studies indicate that some chemical signals are expressed in relation to an individual’s condition and depend, for example, on age, immunocompetence, fertility, body size or degree of inbreeding. Males or females might benefit by choosing based on those traits, gaining resources or “good genes”. Other chemical traits appear to reliably reflect an individual’s underlying genotype and are suitable to choose a mating partner that matches best the own genotype. Full article
(This article belongs to the Special Issue Pheromones and Insect Behaviour)
Open AccessReview Sexual Communication in the Drosophila Genus
Insects 2014, 5(2), 439-458; doi:10.3390/insects5020439
Received: 21 March 2014 / Revised: 14 May 2014 / Accepted: 16 May 2014 / Published: 18 June 2014
Cited by 10 | PDF Full-text (749 KB) | HTML Full-text | XML Full-text
Abstract
In insects, sexual behavior depends on chemical and non-chemical cues that might play an important role in sexual isolation. In this review, we present current knowledge about sexual behavior in the Drosophila genus. We describe courtship and signals involved in sexual communication, [...] Read more.
In insects, sexual behavior depends on chemical and non-chemical cues that might play an important role in sexual isolation. In this review, we present current knowledge about sexual behavior in the Drosophila genus. We describe courtship and signals involved in sexual communication, with a special focus on sex pheromones. We examine the role of cuticular hydrocarbons as sex pheromones, their implication in sexual isolation, and their evolution. Finally, we discuss the roles of male cuticular non-hydrocarbon pheromones that act after mating: cis-vaccenyl acetate, developing on its controversial role in courtship behavior and long-chain acetyldienylacetates and triacylglycerides, which act as anti-aphrodisiacs in mated females. Full article
(This article belongs to the Special Issue Pheromones and Insect Behaviour)

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