Browsing by Subject "Entomology"

Now showing 1 - 20 of 27
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    Cold tolerance of drosophila suzukii (Diptera: Drosophilidae)
    (2015-04) Stephens, Amanda Ruth
    Drosophila suzukii Matsumura, or spotted wing drosophila (Diptera: Drosophilidae), is a fly that is believed to be native to Japan. Spotted wing drosophila females lay eggs into ripe and ripening soft skinned fruits, where larvae develop. The species was first found in the continental United States in 2008, where it was reported to cause extensive economic damage in many fruit crops, including raspberry, blackberry, blueberry and cherry. Spotted wing drosophila is believed to overwinter as a seasonally acclimated winter morph adult. While spotted wing drosophila is found in northern states with colder climates, the ability of it to establish and overwinter in these regions is unknown. Likelihood of spotted wing drosophila overwintering survival was hypothesized by reviewing literature on other Drosophila species cold tolerance. Cold tolerance of spotted wing drosophila was then measured by comparing the supercooling points and lower lethal temperatures of seasonally acclimated (winter-morphs) and non-acclimated adults (summer-morphs). The ability of winter-morphs and summer-morphs to rapidly cold-harden was also studied to determine if the fly can quickly acclimate to new cold temperatures.
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    Comparison of emergence and taxonomic composition of chironomidae (Insecta: diptera) in Tortuguero National Park, Costa Rica.
    (2012-01) Kranzfelder, Petra
    Traditional methods of collecting aquatic macroinvertebrates can be time consuming and expensive. One efficient form of sampling involves collection of surface floating pupal exuviae (SFPE) of a group of aquatic flies of the family Chironomidae. Previous studies have shown the efficacy of the SFPE collection technique to determine chironomid taxonomic composition and temporal organization in small streams of northwestern Costa Rica. However, the methodology has never been employed in a Neotropical brackish water setting and its efficacy was unknown in this context. The primary goal of this study was to test the SFPE method in a Neotropical brackish water setting and to expand the knowledge base of chironomid taxonomy and ecology in Costa Rica. The objectives of this research were to determine the economy of the SFPE method for studies in Neotropical brackish waters and the variability of Chironomidae emergence and taxonomic composition. Collections of chironomid SFPE were made in the brackish water estuary, Laguna del Tortuguero, and freshwater stream, Quebrada, in Tortuguero National Park, Costa Rica on seven consecutive days during both the dry and wet seasons. The SFPE method appears to be a reasonably economical method for sampling Chironomidae in Neotropical brackish waters and it is successful in detecting spatial differences in emergence between sites in the dry and wet season. The results indicate that Chironomidae SFPE sampling could be employed as part of a rapid biomonitoring program for monitoring water and sediment quality in Tortuguero National Park, Costa Rica. Generally, these data will expand the knowledge base of Neotropical Chironomidae taxonomy and ecology, which will facilitate entomological and aquatic ecology research and teaching in Latin America.
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    Corn earworm (Helicoverpa zea Boddie), cold hardiness, and climate change: implications for future distributions and IPM.
    (2010-09) Morey, Amy Claire
    The cold hardiness of Helicoverpa zea (Boddie) pupae was assessed using three laboratory methods: supercooling point (SCP), lower lethal temperature (LLTemp), and lower lethal time (LLTime) determination. Mean SCPs for pupae ranged between -16.4°C and -19.5°C, depending on whether pupae were in diapause or had been acclimated. The LLTemp at which 50% mortality occurred (LT50) for diapausing and non-diapausing pupae was -8.8°C and -12.4°C, respectively, though the LLTemp mortality curves were not significantly different. The time until 95% mortality for non-diapausing pupae held at -10°C, -5°C, 0°C, and 5°C was 7.2, 81.6, 502.3, and 1073.4 hrs, respectively. Time until 95% mortality for diapausing pupae held at 0°C and 5°C was 2660.19 and 2796.92 hrs, respectively. Sex did not have an influence on cold hardiness. Diapause greatly enhanced cold hardiness in pupae as indicated by a significantly lower mean SCP and longer time to reach mortality at a given temperature compared to non-diapausing pupae. However, given mean SCP comparisons, acclimation of non-diapausing pupae had a cold hardening effect comparable to diapause. In-field evaluation of overwintering H. zea survival in southern Minnesota showed that temperature was a severely limiting factor in overwintering success, though likely not responsible for complete mortality. Laboratory data, coupled with the field results suggest that a small proportion of pupae may be able to survive in Minnesota. However, field observations also suggest that sufficient degree days may not be available during autumn in southern Minnesota to allow for substantial pupation before the onset of winter, thus eliminating the potential for an overwintering population. Using the cold hardiness data generated for diapausing pupae, the present and future distributions of H. zea in North America were calculated with the modeling software CLIMEX. The resulting maps depicting the current distribution of H. zea from CLIMEX did not agree with what is currently understood for H. zea overwintering distributions and overall geographic suitability; contrary to convention, cold stress is shown to not be a significant constraint to H. zea suitability for most of the U.S. Despite the discrepancies in current projections, the present study corroborated Diffenbaugh et al. (2008) in illustrating a northern expansion of suitability for H. zea, under future climate change. The implications of potential northern expansion in the geographic range of H. zea are discussed within the context of future Integrated Pest Management (IPM) needs for sweet corn, as well as other vegetable and field crops throughout North America.
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    The Effects of Nosema ceranae on honey bee health
    (2014-10) Goblirsch, Michael James
    Honey bees are arguably the world's most iconic pollinator. The presence of honey bees in our landscapes has long invoked images of vitality, diligence, and cooperation. Unfortunately, the current state of honey bee health and productivity paints a rather different picture for this beneficial insect. The survival of honey bees, as well as the livelihoods of those who benefit from their labor (e.g., beekeepers, growers, and ranchers) is under threat from the culmination of a number of detractors to bee health. Exposure to pesticides, poor forage, mite parasites, and pathogens has resulted in heavy annual death of honey bee colonies in the U.S., Europe, and other parts of the world. Among the suspects thought to contribute to bee decline, the fungal pathogen, Nosema ceranae, is found at high prevalence in both healthy and declining/dead colonies. Since N. ceranae is thought to be a novel pathogen of the European honey bee, Apis mellifera, much remains unknown about its pathology at the individual and colony levels, as well as how infection may interact to form synergisms with other factors thought to be responsible for declining honey bee populations. Here, I review the breadth of research conducted on Nosema infection of honey bees in general. I give particular attention to observations on the detection of infection, cytopathology, viability and infectivity of spores, and incidence and geographic distribution. I rely on what is known about a similar and long-recognized pathogen of A. mellifera, N. apis, for context on the host-parasite relationship of Nosema infection of honey bees. As one part of my dissertation research, I applied background information about the effects of infection on the different castes to show how this may disrupt the social structure of a honey bee colony and contribute to its decline. The level of a honey bee colony or even a whole bee are complicated systems to study intracellular microbes such as Nosema that threaten honey bee health and productivity. Continuous cell lines have been lacking to further our understanding of the pathogenicity of Nosema infection in a simplified environment removed from the confounding effects of other factors such as poor nutrition or pesticides. For the second part of my dissertation research, I addressed this deficiency in honey bee research by developing an in vitro system derived from host cells that could be utilized for observing infection in a simplified environment. Whenever possible, I provide suggestions for future research that could broaden our understanding of this pathogen and ultimately improve honey bee health.
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    Entomology Department Newsletter 2014
    (2014) University of Minnesota Entomology Department
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    Entomology Department Newsletter, 2011
    (University of Minnesota: Department of Entomology, 2011)
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    Entomology Department Newsletter, 2013
    (2014-04-11) University of Minnesota, Department of Entomology
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    Entomology Department Newsletter, 2015
    (2015) University of Minnesota Entomology
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    Entomology Department Newsletter, 2016-17
    (2017) University of Minnesota Entomology Department
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    Entomology Newsletter 2012
    (2012) University of Minnesota Entomology Department
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    Entomology Newsletter Volume 2 '85-86
    (1986) University of Minnesota, Entomology Department
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    Entomology Newsletter Volume 5 '88-'89
    (1989) University of Minnesota, Entomology Department
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    Entomology Newsletter Volume 6 '89
    (1989) University of Minnesota, Entomology Department
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    Entomology Newsletter, Volume 4 '87-'88
    (1988) University of Minnesota, Entomology Departmant
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    Flight capacity of emerald ash borer Agrilus planipennis (Coleoptera: Buprestidae) and its parasitoid Tetrastichus planipennisi (Hymenoptera: Eulophidae), in response to several experimental treatments
    (2014-12) Fahrner, Samuel Joseph
    Emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive beetle native to eastern Asia. Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) is one of three hymenopteran parasitoids currently being introduced into North America as part of a classical biological control program against emerald ash borer. Here, custom-built, computer-monitored flight mills were used to measure the effects of age, feeding status, mating status, sex, and size on flight metrics of T. planipennisi. The flight mill was then used to measure flight metrics of emerald ash borer and T. planipennisi across a range of temperatures and relative humidity. The relationship between flight energetics, specifically flight distance, with temperature was then integrated with landscape temperatures at ten locations throughout the continental United States to compare relative dispersal capacity for emerald ash borer and T. planipennisi. The goal of this research was to elucidate factors that mediate the flight capacity of both insects and, for T. planipennisi, to infer the pre- and post-release conditions that may optimize flight capacity.
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    Host acceptance behavior in the soybean aphid parasitoid Binodoxys communis (Hymenoptera: Braconidae) - the role of physiological state in biological control.
    (2011-07) Dieckhoff, Christine
    Host choice behavior in insect parasitoids and herbivores has been predicted to vary dynamically in response to external and internal factors acting on a foraging female; physiological state and egg load in particular have been shown to play a major role. In my dissertation, I addressed the role of physiological state in parasitoid host choice behavior at the host species level under field conditions. The parasitoid of choice was the classical biological control agent Binodoxys communis Matsumura that has been released in 2007 throughout the Midwestern USA as part of a classical biological control project against the invasive soybean aphid, Aphis glycines (Gahan). First, I designed a series of laboratory experiments to assess egg load and the risk of egg limitation in female B. communis in response to temperature, sugar feeding, and host availability. These experiments showed that B. communis maintains a constant egg load by varying its egg maturation rate in response to oviposition events. I hypothesized that such a rapid egg maturation might help minimize the risk of egg limitation under field conditions. Therefore, in the summers of 2007 and 2008 I conducted a release-and-recapture study to assess egg load and nutritional state of field-collected parasitoids and was able to show that the majority of female parasitoids maintained a relatively constant egg load under field conditions. In the summer of 2009, I designed a no-choice test that explicitly addressed host choice behavior in field-collected B. communis. Host specificity in B. communis was maintained in field-collected females, but low host availability and detrimental weather conditions increased the likelihood of females accepting the low-quality host species. In the summer of 2010, I designed a field study that assessed the host choice behavior in free-foraging B. communis. Overall, the results of both laboratory and field studies strongly suggested that B. communis maintained a high level of host specificity.
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    The influence of mid-continent agricultural land use on the health and survival of commercially managed honey bee (Apis mellifera L.) colonies
    (2015-02) Smart, Matthew
    Commercial honey bee colonies were assessed in six apiaries that varied in their land use composition, in the Prairie Pothole Region of North Dakota over three years, 2010-2013. All colonies were transported to California to pollinate almonds each fall and were transported back to North Dakota each spring. The goal of the study was to determine the factors that most influenced, and thus predicted, annual survival of colonies in the different apiaries from summer through the following spring. The factors were grouped into three levels of analysis: 1) land use surrounding the North Dakota summer apiaries, including floral availability and pesticide exposure; 2) colony-level measures of population size, pollen and honey stores, queen status, and presence and prevalence of parasites and diseases; and 3) individual bee-level measures of nutritional physiology and immunity in 7-day old nurse bees collected from healthy colonies within each apiary. Results indicated that the area of uncultivated land (including CRP lands, pasture, grassland, flowering trees and shrubs, fallow land, hayland, and ditches) exerted a significant positive influence on the annual proportion of colonies surviving among apiaries. At the colony level, the amount of brood (pupae) in September and the mean pollen (g) collected per day over the summer correlated with higher annual survival. Higher Varroa destructor mite infestation levels in September were associated with reduced overwinter survival. Individual bee measures positively influencing survival included the expression level of vitellogenin in September and abdominal lipid stores in August. The expression level of lysozyme-2 in September was related to decreased apiary survival. A final, integrated model, incorporating all of the significant factors across the three levels, revealed that all, except Varroa levels, remained significant as predictors of annual colony survival within apiaries. Varroa was actively and effectively controlled by the collaborating beekeeper; thus in this study was not an overall contributor to colony mortality. This is the first study to quantify the impact and importance of pollen nutrition; i.e., "pollen flow" from the level of landscape to the individual-bee, to the health and survivorship of colonies. The most significant predictors of health and survivorship across all three levels of analysis were all related to nutrition - beginning with abundant flowers located overwhelmingly in uncultivated lands. More and/or better forage led to greater honey production and pollen collection which in turn led to greater nutritional stores in individual bees, and an overall decreased immune response. The presence of quality and abundant forage surrounding summering locations support healthy, robust, and most importantly, surviving, colonies of honey bees.
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    A monographic revision of Euchaetes Harris (Lepidoptera: Erebidae: Arctiinae)
    (2014-12) Hendrickson, Heather Marie
    Euchaetes Harris, 1841 is a genus of subfamily Arctiinae, family Erebidae. The genus is distributed throughout the New World, with diversity spanning southern Canada, North America, and Central America. The following is a monographic treatment of the genus. A species-level revision of Euchaetes is completed examining 41 species representing 18 ingroup and 23 outgroup species, scoring a total of 75 morphological characters (191 states) including: head, appendages, male genitalia, female genitalia. The revision treats 18 species, including three newly described species: Euchaetes donahuei, Euchaetes gravastellus, and Euchaetes harveyi. All species are fully illustrated with adult habitus and male and female genitalia (when both were available for study). When known, the biology of a species is summarized. Range maps for each species are also provided based upon the material examined in this study. The type of Euchaetes scepsiformis Graef, 1887 is established as the neotype for Euchaetes bolteri Stretch, 1885. Pygoctenucha Grote, 1883, is placed as a junior subjective synonym of Euchaetes Harris, 1841, based on male and female genitalic characters and the placement of the type species P. terminalis within the Euchaetes clade in the phylogenetic analysis. Former species of Pygoctenucha are placed in Euchaetes as either sensu lato (E. enna, E. azteca) or incertae sedis (E. pyrrhoura and E. clitus). Euchaetes bicolor Rothschild, 1935 is transferred to Agaraea Herrich-Schäffer, 1855 based on its shared adult habitus--body shape, wing shape, and wing venation. Euchaetes fusca (Rothschild 1913) is transferred to Cycnia Hübner, 1818 based on the orb-like uncal processes on the male genitalia and presence of rayflower-like signa in female bursae. Additionally, Pagara Walker, 1856 is placed as a junior subjective synonym of Agaraea Herrich-Schäffer, 1855 based on the shared morphology of the male genitalic capsules.