AN ABSTRACT OF THE THESIS OF Fares Alzahrani for the degree of Master of Science in Crop Science on July 15, 2019. Title: Elucidating Key Aspects of the Biology of Select Species of Snail-killing Flies (Diptera: Sciomyzidae) in Oregon. Abstract approved: ______________________________________________________ Rory J. McDonnell 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. ©Copyright by Fares Alzahrani July 15, 2019 All Rights Reserved Elucidating Key Aspects of the Biology of Select Species of Snail-killing Flies (Diptera: Sciomyzidae) in Oregon. by Fares Alzahrani A THESIS Submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented July 15, 2019 Commencement June 2020 Master of Science thesis of Fares Alzahrani presented on July 15, 2019 APPROVED: Major Professor, representing Crop Science Head of the Department of Crop and Soil Science Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Fares Alzahrani, Author ACKNOWLEDGEMENTS I must first express my sincere gratitude and appreciation to my major advisor Dr. Rory Mc Donnell for his guidance, unlimited support, and high standards. This research was possible because of his mentorship. Also, I would like to thank my committee members, Dr. Andrew Hulting, Dr. Gail Langellotto, and Dr. Klaus Puettmann for their encouragement, useful ideas, and recommendations. A special thanks to Andy Colton, who supported me throughout my research and was always available when I asked for his help. Thanks also to my lab members, Dr. Inga Reich, Dr. Maria Cordoba, Dr. Casi Jessie, and Matt Klein for their support in the lab and the field. Thanks to Dr. Nik Wiman for providing us the flight mills and sharing his experience. Also, I would like to thank all of the E.E. Wilson Wildlife Area staff for their assistance during field collecting. I also greatly thank my sponsor, Saudi Arabia Culture Mission (SACM), for fully funding my graduate studies. Finally, I would love to thank my parents, Ahmed and Salha, my wife, Asma, my daughters, Wateen, Aleen and Hems, and all my friends in Saudi Arabia and in the USA for their love, support, and everything they have done for me. TABLE OF CONTENTS Page Chapter 1: General Introduction …..……………………………………………..…………...….1 Sciomyzidae ……….……………………………….…………………………………1 Feeding Behavior and Phenology of Sciomyzidae ………………………….…….…3 Biological Control Potential …………………….…………………………….……....4 Focal Species of the Thesis …………………….……………………………….….....7 Chapter 2: Trail following behavior and survival in neonate larvae of Tetanocera obtusifibula ….…………………………………….……………………………………………………..……8 Abstract ..…….…..…………….….........………………..…………………………8 Introduction ..………..………….….………………..……………………………….9 the objectives of this Study ......……....……….………..…...……………………..….11 Materials and Methods ….….….……..………………………………………..……….….11 Sciomyzidae Collection and Rearing .…….………………...……..11 Trail Following ....…........................................................………….13 Larval Survival …..............................................….………………..15 Statistical Analysis …………..……………………………………..15 Results ………………..……...………………………………..…………………………...16 Trail Following ...…………………….……………………………...16 Larval Survival ……………………………………………………...17 Discussion .………...…..…………………………..…………………………………...….18 Trail Following ……...……………………………………………...18 Larval Survival ……………………………………………………..20 Chapter 3: Flight behavior of Sepedon fuscipennis (Diptera: Sciomyzidae) on a flight mill …..21 Abstract…...……………………….....……………………………………21 Introduction ….…..………...….………………..…………………………22 Materials and Methods ….……….………………………………………..………………..24 Sciomyzidae Collection and Rearing ……..…………………….……24 Flight Mills …………………………………………………………...25 Statistical Analysis….…………………………………………………26 Results ..……………………………………………………………………………………27 Total Flight Distance..…………………..…………………………………………27 Flight Velocity………………………………..…………………………………...30 Longest Single Flight …..……...……………………….………………….……..33 Total Flight Time ...........................................................................................…...36 Discussion ……....………...………………………………………………….…………....40 Chapter 4: Conclusion and Future Research …….………………………………………….… 43 Trail Following …………………………..…………………………………….……..43 Larval Survival ………………………………………………………………….……44 Flight Mills ………...……...…………………………………………………….…....45 Bibliography ……...…………………………..………………………………….……………..47 LIST OF FIGURES Figure Page 1.1 Life cycle of a typical sciomyzid Sepedon spinipes …...…………………………………...2 2.1 Jackson Frazier Wetland, 3460 NE Canterbury Cir, Corvallis, OR 97330………………....11 2.2 Material used for maintaining T. obtusifibula in the lab ……….………………….…...…..12 2.3 Materials used to collect sciomyzid eggs ………………………………….……….…...….13 2.4 Filter paper Y-maze used to conduct trail following bioassays ……...………………....….14 2.5 The number of T. obtusifibula neonate larvae that displayed a positive trail following response and no response to fresh mucus trails of Lymnaea sp …………………………..........16 2.6 The number of T. obtusifibula neonates that displayed a strong response (SR), medium response (MR) and a weak response (WR) to fresh mucus trails of Lymnaea sp ……………………………………………………………………………………………….….17 3.1 E. E. Wilson Wildlife Area, Camp Adair Rd, Monmouth, OR…………….………….....…25 3.2 Flight mill utilized to investigate the flight behavior of S. fuscipennis………………….......26 3.3. Mean (+SE) total distance (km) flown for males and females of S. fuscipennis ………......28 3.4 Mean (+SE) total distance (km) flown for fed and unfed flies of S. fuscipennis.…………...29 3.5 Mean (+SE) total distance (km) flown by adult S. fuscipennis under enhanced humidity and ambient humidity conditions ……………….……………………………………...……….…..30 3.6 Mean (+SE) velocity (km/h) for males and females of S. fuscipennis ………..……….……...31 LIST OF FIGURES (Continued) Figure Page 3.7 Mean (+SE) velocity (km/h) for fed and unfed adults of S. fuscipennis ….………….…….32 3.8 Mean (+SE) velocity (km/h) of adult S. fuscipennis under enhanced humidity and ambient humidity conditions ……………………………………………………………………...…...33 3.9 Mean (+SE) longest single flight (km) for males and females of S. fuscipennis …….......34 3.10 Mean (+SE) longest single flight (km) for fed and unfed adults of S. fuscipennis……....35 3.11 Mean (+SE) longest single flight (km) for adult S. fuscipennis under enhanced humidity and ambient humidity …………………………………………………………………………….…………..……………..…...36 3.12 Mean (+SE) total flight time (h) for males and females of S. fuscipennis ………………..37 3.13 Mean (+SE) total flight time (h) for fed and unfed adults of S. fuscipennis ……..…........38 3.14 Mean (+SE) total flight time (h) for adult S. fuscipennis under enhanced humidity and ambient humidity conditions ….…………………………………………………………......….39 LIST OF TABLES Table Page 1.1 Known phenological groups within the family Sciomyzidae …………………...….5