Graduate Thesis Or Dissertation


Elucidating Key Aspects of the Biology of Select Species of Snail-killing Flies (Diptera: Sciomyzidae) in Oregon Public Deposited

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  • Members of the family Sciomyzidae, known as snail-killing or marsh flies, are unique amongst insects in that the vast majority of reared species feed exclusively on mollusks and as a result their biological control potential has been well documented in the scientific literature. However, in North America there is a lack of information on many aspects of the biology and behavior of these flies which has hampered their consideration and use as biological control agents of pest gastropods. This knowledge gap provided the incentive for this thesis which focused on two species, namely Tetanocera obtusifibula and Sepedon fuscipennis. The specific aims were to 1) determine if neonate larvae of T. obtusifibula can follow fresh snail mucus trails; 2) investigate the effect of temperature (10°C, 15°C, 20°C, ~4°C and outdoors) on the survival of unfed neonate T. obtusifibula larvae; and 3) elucidate the flight behavior of an adult sciomyzid fly for the first time using S. fuscipennis as the target species. The trail following bioassays were conducted on filter paper Y mazes, and significantly (P<0.05) more larvae displayed a positive response i.e. moved fully into the trail arm (73.9%) than a non-response i.e. did not trail follow (26.1%). Of those that displayed a positive response, 60% followed the trail to the end and 40% followed the mucus at least to the midpoint. These data suggest that larvae of T. obtusifibula actively seek out their prey and are may be effective hunters. In general, unfed neonate survival for this species decreased with increasing temperature. Thus, from a biological control perspective released neonate larvae may have less time to find suitable snail prey if they are released during warm summer days compared to cooler days during the fall. The flight mill data demonstrated that these flies have the potential to fly for a long distance (up to 25km in 24hrs on a flight mill) which is contrary to the current school of thought. This result also has important implications for using sciomyzids such as S. fuscipennis in biological control programs. For example, the ability to disperse over large distances could be viewed as advantageous for augmentative release programs utilizing native sciomyzid species where the goal is to manage a gastropod pest over a large area. Conversely, in cases of classical biological control, it will be necessary to exercise caution because non-target effects may have a broader geographical post release range than previously thought. Lastly, avenues for potential future research are suggested.
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  • Intellectual Property (patent, etc.)
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  • 2019-09-25 to 2020-10-26



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