Entomology

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Research from the Department of Entomology. The department is part of the School of Natural Resources, and their website may be found at https://www.ndsu.edu/snrs/

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    Behaviors Mediate Aphid Interactions with Natural Enemies and the Environment
    (North Dakota State University, 2016) Kopco, James
    Behavior is a crucial component of ecology that mediates how animals interact with one another and with the environment. Behaviors can allow animals to avoid the harmful effects of things like competition, predation, and extreme abiotic conditions. However, animals often have constraints that limit the potential benefits of their behaviors, so we addressed what factors contribute to these constraints in plant-aphid-wasp systems. Parasitoids of aphids are tiny wasps that lay their eggs in aphids, where the larva feeds and develops. Each aphid can only sustain a single parasitoid, so parasitoids mark aphids when they lay an egg to discourage others from laying additional eggs. Not all parasitoids mark aphids the same way, and whether species with different marks can recognize one another’s mark was unclear. We found that parasitoids with different marks fail to respond to one another’s marks. Because these parasitoids laid eggs in aphids that were already parasitized, competition between them will occur through mortal combat between the larvae rather than egg-laying restraint in the adults. Parasitoid attack induces aphid behaviors such as fighting, running away, or dropping off the host plant. These behaviors can deter or evade the attacker, but they cost the aphid an opportunity to feed. This feeding interruption decreases the number of offspring the aphids produce. When aphids run from a threat, they usually resettle on the newest leaves of a plant, where their reproduction is enhanced. However, when they drop from a plant to escape, they resettle randomly and do not benefit from the better location, indicating that more vigorous responses can lose benefits. We also showed that aphids exhibit similar movement and resettling behaviors when disturbed by heat shocks. However, this behavior did not affect aphid reproduction or survival when induced by a heat shock. While movement to new leaves appears to be a general response to several disturbances, its benefits to aphids only occur in specific situations. We have shown that behaviors can be constrained by unfamiliar stimuli and the general context in which they are invoked. These constraints can dictate how insects interact with each other and the environment.
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    Conspectus of Aeptini Stål, 1871 (Hemiptera: Heteroptera: Pentatomidae: Pentatominae)
    (North Dakota State University, 2017) Faúndez, Eduardo I
    The Pentatominae tribe Aeptini is revised. A key to the known genera is provided, together with redescription and figures. The genus Paramenestheus is revised, including a key to the species and figures to all the included taxa. Two new genera and eight new species are discovered and described. A phylogenetic analysis is included for the Aeptini, with two approaches, cladistic and maximum likelihood, both morphologically based. After these analysis it is concluded that it is a monophyletic tribe and has to be split into two subtribes: Aeptina (including Aeptus and Eribotes) and Menesthina (including Aeliosoma, Hillieria, Menestheus, Paramenestheus, Pseudaelia, New Genus 1, New Genus 2.). Diagnoses for both subtribes are included. Biogeographically it is hypothesized that the Aeptini have a Gondwanian origin which explains it current disjunct distribution in Africa and Australia. The importance of the findings on this dissertation, as well as the relationships among Aeptini and other Pentatominae groups is commented and disccused. Special reference is made to the importance of the presence of a mesosternal sulcus as a major character that may lead to a reclassification of the Pentatominae, having the Aeptini as one of the basal groups. After all the changes proposed on this dissertation the Aeptini is now comprised of two subtribes, nine genera and 30 species.
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    Effects of Temperature on Pea Aphids, their Host Plants, and their Parasitoids
    (North Dakota State University, 2018) Valls, Aleix
    Temperature has the potential to alter every aspect of an organism’s biology. This is especially true when we focus on small ectotherms such as insects. Understanding the effects of temperature on insects is particularly important given that climate change scenarios predict changes in temperature across the globe. In Chapter 1 we explored the effects of heat shocks on a discrete host-parasitoid interaction, specifically asking what happens if the heat shock happened before, during or after the interaction. We found that heat shocks had a stronger negative effect when they occurred while the wasp was actively foraging. In a follow-up behavioral experiment, we observed that this result is likely caused by the heat shock quickly rendering the majority of wasps inactive. In Chapter 2 we tested how variation in temperature affects pea aphid population size and how the effect changes with average temperature. We compared the population size of pea aphids under constant and fluctuating temperature profiles across a cool temperature range (20C and 16C/24C) and a warm temperature range (28C and 24C/32C). We saw that in the cooler range, pea aphids in the constant and fluctuating temperature treatments had the same population size. However, the same was not true for the warmer temperatures. In that case, fluctuating temperature profiles produced smaller populations compared to the constant temperatures. In Chapter 3 we focused on the possible indirect effects of temperature on pea aphids mediated by the aphids’ host plants. We performed five experiments where we manipulated the exposure temperature (16C, 24C, and 32C) for plants and aphids. While temperature had strong direct effects on aphids and also affected plant size, temperature had little to no indirect effects on pea aphid fecundity. While the idea of temperature change can seem straightforward, temperature effects on insects are not straightforward. Timing and variation of temperature change are important. Indirect effects though direct effects on hosts also are important. My work shows a number of approaches for investigating these different temperature effects to better understand what might happen to insects when climate changes.
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    IfSAR DTM-derived Predictive Flood Models: A Cost-effective Approach to Target Site- Specific Mosquito (Diptera: Culicidae) Control Efforts
    (North Dakota State University, 2016) Stenehjem, Jacquelin J.
    The study area is the 400 km2 floodplain and wetlands of the upper Missouri River, located in the northwestern corner of North Dakota, near the community of Williston. Regional climate is semiarid, yet the Williston vector control agency battles large populations of Culicidae nearly every spring and summer. Best mosquito management practices (BMPs) are integrated, relying on a combination of thorough, routine, ground-based sampling and surveillance methods to provide important information on which control strategies and evaluations of effective are based. However, the mosquito breeding habitat near Williston is extensive and contains difficult terrain, which makes standard ground-based sampling and surveillance methods impractical. This study analyzed remotely sensed Interferometric Synthetic Aperture Radar (IfSAR) Digital Terrain Model (DTM) elevation data as a potential alternative for ground-based methods. Remotely sensed IfSAR technology is relative low-cost, has high-spatial resolution, is not limited by inclement weather, and only needs to be collected once if local topography remains stable. IfSAR elevation data provides information needed to model hydrological characteristics such as slope, aspect, water flow direction, and accumulation, important considerations in relation to mosquito control efforts. Predictive flood models, developed in this study from the IfSAR elevation data, make it possible to predict the locations of water accumulation within the floodplain as river elevations fluctuate. A vertical root mean squares error (RMSEz) assessment of the full IfSAR elevation data in all land cover classifications combined was 1.071 m, consistent with the vendor’s stated RMSEz of 1 meter. The vertical accuracy of the full IfSAR data was 2.099 meters at the 95% confidence level and is consistent with the 95th percentile accuracy of 2.211 meters. The frequency distribution of errors was generally normal. This study determined that airborne, high-resolution IfSAR DTM-elevation data can serve as an alternative for ground-based sampling and surveillance methods and provide a needed decision support system (DSS) tool to the local vector control agency. The predictive flood models are a new approach for predicting the locations of accumulated water within the floodplain will decrease vector control response time and improve the targeting of site-specific control efforts, which in turn, will decrease overall costs for these services.