AN ABSTRACT' OF THE THESIS OF Tracey M. Anderson for the degree of Doctor of Philosophy in Entomologypresented on 12 April 19%. Tide: Life History and Larval Ecology ofArrenurus hanzrumi alydrachnida: Arrenuridaej Redacted for Privacy Abstract approved: N. H. Anderson in semiarid rangelands, a variety of permanently wet habitats canbe classified within the broad category of springs. 'The aquatic arthropod communitiesin these habitats are poorly studied compared to larger streams and rivers. A surveyof springs in the Bridge Creek drainage in Wheeler Co., OR revealed anaquatic insect community that differed from that of Bridge Creek in taxonomic compositionand trophic structure. Very few species from aquatic insect orders (Ephemeroptera, Plecoptcra,Trichoptera) were collected from springs, but Diptera were very diverse. Argia vivida, a damselfly that occurred at all springs that weresurveyed, was parasitized by larvae of the water miteArrenurus hamrumi.A. hamrumi is a new species of water mite for which all life stages were associated anddescribed. The biology of the mite and its association with A. vivida were the focus ofsubsequent research in this thesis. Adults and dcutonymphs of A.hanzrumiare predators of ostracods,which are abundant in the detritus-based benthic community ofthe springs. Larvae of A.hamrtuni may be phoretic on damselflylarvae for several months prior to parasitizing the adult stage. Parasitic larvae may occur in high numbers on A. vivida,resulting in mortality of both damselflies and mites. Mite larvae that survive the parasitic phase must return tothe water to complete the life cycle. Exposure to the zone of highrelative humidity over the springs, where damselflies often perch, initiates detachment of mite larvaefrom male and female damselflies. This research provides an example of how data from a faunal surveycontribute to several bodies of knowledge including the biodiversity and community structureof spring habitats, the systematics of the water-mite genus Arrenurus, and life-historyadaptations of water mites and of spring-dwelling organisms. LthE HISTORY AND LARVAL ECOLOGY OF ARRENURUSHAMRUMI (HYDRACHNIDA: ARRENURIDAE) by Tracey M. Anderson A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Presented April 12, 1996 Commencement June 1996 Doctor of Philosophy thesis of TraceyM. Anderson presented on April12, 1996 APPROVED: Redacted for Privacy Major Professor, representingEntomology Redacted for Privacy Chair of Departme f Eititomology Redacted for Privacy Dean of Gradu School collection of Oregon State I understand that my thesiswill become part of the permanent University libraries. My signaturebelow authorizes release of mythesis to any reader upon request. Redacted for Privacy Tracey M. Anderson, Author ACKNOWLEDGMENTS I would like to extend my sincere appreciation to my major professor, N.H. Anderson for all his help and support throughout my graduate program. Norm gave me the freedom to pursue my own course of research, while still holding me to his high expectations and standards. While he never will change my mind about the beauty of the central Oregon desert, he has influenced me in many ways that I feel have made me a better scientist and teacher. I must also recognize contributions of the rest of my graduate committee. Jerry Krantz generously shared his expertise in acarology and allowed me the use of his microscope. Bill Stephen and Jack Lattin provided support and guidance throughout my degree program. Bill Krueger served as my minor professor. His attitudes toward graduate education were refreshing and greatly appreciated. Special thanks go to Porter Lombard, my graduate representative, for making the trip up from Medford for my preliminary and final exams. I benefited greatly by interacting with the small, but devoted, cadre of water mite fans in North America. Ian Smith of Agriculture Canada was instrumental in my initial decision to study water mites. He made invaluable contributions to the species description and was a great resource in all aspects of my research. Without his input and enthusiasm I doubt that I could have come this far. Bruce Smith of Ithaca College provided information on Arrenurus and was very generous with his time when I visited his lab. The faunal survey of springs in central Oregon was funded by the USDI Geological Survey Award No. 14-08-001-G2041 to the Water Resources Research Institute at Oregon State University. Brad Keller, formerly of the Prineville District of the Bureau of Land Management, showed me many of the springs that were included in this research and provided me with a trailer in the field for two summers. I would like to thank Wayne Holme of the Painted Hills Unit of the John Day Fossil Beds National Monument and the people of Mitchell, Oregon for making my field work more fun and interesting than I could have ever hoped. The assistance and support of many people in the Department of Entomology are also gratefully acknowledged. I specifically would like to recognize Ralph Berry, Mike Burgett, Jo Christensen, Martin Dieterich, Mike Lamana, Mark Mankowski, Pete Oboyski, Gary Parsons, and Frank Radovsky. Lastly, I would like to thank my parents and grandparents for their unfailing confidence in me and support of my graduate studies. I hope they share my sense of accomplishment because they certainly contributed a great deal. CONTRIBUTION OF AUTHORS Dr. Ian M. Smith of the Biosystematics ResearchCentre, Agriculture Canada, verified that Arrenurus hamrumi was a previouslyundescribed species of water mite. He made valuable suggestions on the speciesdescription and provided useful morphological comparisons with other water mite taxa. TABLE OF CONTENTS Page INTRODUCTION 1 THE INSECT FAUNA OF SPRING HABITATS INSEMIARID RANGELANDS IN CENTRAL OREGON 3 ABSTRACT 4 INTRODUCTION 4 HABITAT CHARACTERIZATION 5 AQUATIC INSECT COMPOSITION 8 Methods 8 Taxon Richness 11 Functional Feeding Groups 16 DISCUSSION 18 ACKNOWLEDGMENTS 22 LITERATURE CliED 23 ARRENURUS HAMRUMI (HYDRACHNIDA: ARRENURIDAE), ANEW SPECIES OF WATER MITE FROM RANGELAND SPRINGSIN CENTRAL OREGON 25 ABSTRACT 26 INTRODUCTION 26 ARRENURUS (ARRENURUS) HAMRUMI, SP. NOV 27 Larva 27 Deutonymph 31 Male 31 Female 34 Type Material 38 Host Relationships 38 Habitat and Distribution 38 TABLE OF CONTENTS (Continued) Page DISCUSSION 39 REFERENCES 41 LIFE HISTORY OF ARRENURUS HAMRUMI, A WATER MITE FROM RANGELAND SPRINGS IN CENTRAL OREGON, USA 42 INTRODUCTION 43 STUDY AREA 46 METHODS 51 Field Collecting 51 Laboratory Procedures 53 L1PE HISTORY OF ARGIA VIVIDA 54 LIFE HISTORY OF ARRENURUS HAMRUMI 57 Adult Stage 57 Egg Stage 58 Larval Stage 60 Post larval Development 65 Seasonal Occurrence of Life Stages 67 DISCUSSION 68 REFERENCES 72 DETACHMENT OF ARRENURUS HAMRUMI LARVAE (HYDRACHNIDA: ARRENURIDAE) FROM ARGIA VIVIDA (ODONATA: COENAGRIONIDAE) 76 ABSTRACT 77 INTRODUCTION 78 METHODS 81 TABLE OF CONTENTS (Continued) Page RESULTS 86 DISCUSSION 89 REFERENCES 94 CONCLUSIONS 95 BIBLIOGRAPHY 98 LIST OF FIGURES Figure Page 2.1. Upper Meyer's Canyon, near Mitchell, Wheeler Co., OR 8 2.2. Stovepipe Spring, Wheeler Co., OR 9 2.3. The proportion of aquatic insect taxa belonging to different functional feeding groups for spring habitats and for Bridge Creek, Wheeler Co., OR 17 2.4. Stovepipe Spring in June 1991 when the distinction between aquatic and terrestrial habitats is obscured 20 3.1 Arrenurus hamrumi, dorsal plate of the larva 28 3.2 Arrenurus hamrumi, venter (A) excretory pore plate (B) of the larva 29 3.3 Arrenurus hamrumi, ventral view of leg segments of the larva 30 3.4 Arrenurus hamrumi, venter of the deutonymph 32 3.5 Arrenurus hamrumi, dorsum of the male 33 3.6 Arrenurus hamrumi, venter of the male 35 3.7 Arrenurus hamrumi, palp (A) and Leg IV (B) of the male 36 3.8 Arrenurus hamrumi, venter of the female 37 4.1 Life cycle of Arrenurus hamrumi (Hydrachnida: Arrenuridae) 47 4.2 Location of the study area in the John Day River system 48 4.3 Stovepipe Spring, Wheeler Co., Oregon 50 4.4 Meyer's Canyon, Wheeler, Co., Oregon 51 4.5 Mean density (+ SE) of Argia vivida and density of those larvae large enough to be hosts of Arrenurus hamrumi (head capsule width > 2.8 mm) in collections from Meyer's Canyon, June 1994-April 1995 56 LIST OF FIGURES (Continued) Figure Page 4.6 Mean density (+SE) of female and male Arrenurus hamrumi in collections collected from Meyer's Canyon, June 1994-April 1995 57 4.7 Life span of Arrenurus hamrumi larvae in the absence of a damselfly host under laboratory conditions 60 4.8 Engorgement of Arrenurus hamrumi larvae 63 4.9 Intensity of parasitism by Arrenurus hamrumi larvae on newly emerged Argia vivida adults compared with intensity of engorged mites on mature damselflies, Meyer's Canyon 64 4.10 Seasonal occurrence of the life stages of Arrenurus hamrumi 68 5.1. The damselfly Argia vivida with engorged larvae of the water mite Arrenurus hamrumi 80 5.2. Cages for damselflies used in manipulative experiments on mite detachment 82 5.3. Individually caged damselflies placed away from the aquatic habitat (LAND, LAND-DRY treatments) 83 5.4. Individually caged damselflies placed over a pan of water in the arid upland environment (LAND- H2O treatment) 85 5.5. The occurrence of water mite larvae on male and female damselflies that were collected while engaged in reproductive activity (copulation, oviposition, or flying in tandem) 87 5.6. The mean percent (+1- SE) of mites detaching from damselflies placed over the water (H2O), over a pan of water away from the aquatic habitat (LAND- H2O), and in the arid upland environment (LAND-DRY) 89 5.7. Perch sites of adult damselflies over Stovepipe Spring and the humidity gradient directly over the aquatic habitat 90 5.8. Humidity transects at three different heights at Meyer's Canyon 90 LIST OF TABLES Table Page 2.1. Water chemistry analysis for spring habitats and forBridge Creek 7 2.2.