AN ABSTRACT OF THE THESIS OF Jon A. Speir for the degree ofDoctor of Philosophy in Entomology presented on August 14, 1975 Title: THE ECOLOGY AND PRODUCTION DYNAMICS OF FOUR BLACK FLY SPECIES (DIPTERA: SIMULIIDAE) IN WESTERN OREGON STREAMS I Abstract approved: Redated for Privacyivacy N. H. Anderson Ecological and production studies of Prosimulium caudatum Shewell, P. dicum Dyar and Shannon, Simulium arcticum Malloch and S. canadense Hearle (Diptera: Simuliidae) were made in 1971 and 1972 in three streams near Corvallis, Oregon.The purpose of the study was to characterize the biology and population dynamics of larvae, and to compare the production of the four species under various spatial and temporal conditions. A total of 54 annual production estimates was derived utilizing 37 stations.In addition, 17 annual drift and 22 emergence (as pupae) determinations were made. Data on the physical and chemical characteristics of the streams, and on larval associates, parasites, predators and food types were obtained at all stations.Laboratory experiments provided data on feeding rates and predator impact. The two Prosimulium species always coexisted, and occurred in all streams. Simulium arcticum and S. canadense were studied in two streams only.All species were univoltine and had egg stage durations exceeding 40 weeks. Prosimulium spp. larvae appeared in mid-February and were on riffles for an average of 10.3 weeks. Simulium arcticum hatching began about six weeks later.Larvae of this species developed in an average of 8.8 weeks. Development of S. canadense began about nine weeks later than for Prosimulium spp. but lasted nearly as long.All four black flies had six larval instars. All larvae were filter feeders, and fed primarily on the sus- pended materials in the streams.Detritus made up from 65-90% of the diet, with the rest being filamentous algae.Alimentary tract clearing of larvae was usually accomplished in less than one hour. Black fly immatures were associated with about 75 other benthic insect species.Of these, nine were likely important simuliid natural enemies.Fish were minor black fly predators. Gastromermis nema- todes occurred in about 3% of all mature simuliid larvae. Annual losses due to drift averaged about 6%.Simuliid drift appeared to be a function of standing crop density.Growth-related crowding may also have been a factor.Effects of diel light conditions, temperature and discharge were minimal. A diel emergence pattern existed for Simulium spp. adults only. The time between emergence and oviposition was likely about 0.5 week for all species.Emergence at most stations was single peaked, and averaged 3. 6 weeks in duration. The sampling universe at each station could be effectively par- titioned to exclude areas where larvae did not exist.Thus, the weekly stratified random sampling program provided population estimates with error terms of usually 15% or less.All quantitative data were expressed on a perm2of overall riffle basis (and not on a perm2of habitat basis) to make the study more comparable to other benthic research. Density, biomass and production differences between stations, streams and years were minimal for each species, and therefore were treated as replicates.Initial densities ranged from over 11000 to about 16000 larvae/m2.Mortality for aggregates of all species was similar, with about 70% of all losses occurring during the first half of larval life.Growth for all species was generally logistic and averaged over 0.090 gig per day annually. Production, averaged for 1971 and 1972, in g/m2 ,was: P. caudatum, 2.644; P. dicum, 2.908; S. canadense, 3. 141; and S. arcticum, 3.950.This species ranking also held for initial density, mean density and mean biomass. Biomass and production were almost always closely correlated.Mortality variations had a greater influence on production than did growth rate. Averaged for all species, the mean total mortality due to drift and parasites was 6.2% and 0.5% respectively.An average of 10.7% of colonizing larvae survived to emerge. Predator-caused losses were estimated to provide the 82.6% needed to balance the loss budget. Black fly larvae were the dominant processor of suspended materials in the three streams. On the average, they outnumbered all other primary consumers combined on riffles by a factor of 27. Simuliid larvae functioned as the primary prey reservoir for as many as 20 species of insect carnivores from Februarythrough June of both years. The Ecology and Production Dynamics of Four Black Fly Species (Diptera: Simuliidae) in Western Oregon Streams by Jon A. Speir A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed August 1975 Commencement June 1976 APPROVED: RERedacted for Privacy Professor of Entomology in charge of major Redacted for Privacy Head of Department of Entomology Redacted for Privacy Dean of Gradate School` Date thesis is presented August 14,1975 Typed by Mary Jo Stratton forJon A. Speir ACKNOWLEDGEMENTS I would like to express my appreciation to the following persons who either assisted with this dissertation or contributed to my educa- tion. To Dr. N, H. Anderson for his help in the preparation of the manuscript, and especially for his guidance and friendship during the time he served as my major professor. To Dr. P.O. Ritcher, ex-chairman of the Department of Entomology, Oregon State University, for his part in gathering entomologists who are both knowledgeable and communicative in all aspects of the discipline. To Dr. C.E. Warren for his counsel on science in general and production in particular. To Drs. G. D, Faulkenberry, N.A. Hartmann and C. Holtz, and especially to Dr, Mary Ann Strand for their guidance on sampling and the statistical analysis of data. To Mr. W. K. Seim for his advice on calorimetry; and to the Department of Fisheries and Wildlife, Oregon State University, for allowing me the unrestricted use of a calorimeter. To my wife, Susan, for her encouragement throughout this research, and for her ability to make the common aspects of life seem extraordinary. This research was ri part supported by the Ecology and System- atics of Aquatic Insects project, Oregon Agricultural Experiment Station, to Dr. N. H. Anderson. TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 3 Aspects of Stream Research 3 Production 6 The Biology of Simuliidae 9 MATERIALS AND METHODS 16 Study Species 16 Study Streams 19 Site Selection and Stations 32 Benthos Sampling and Statistics 33 Drift and Emergence Sampling 42 Biomass and Growth 45 Production 48 Food Types and Feeding Experiments 51 Natural Enemies 53 RESULTS AND DISCUSSION 55 Species Composition and Habitat Segregation 55 Life History 59 Egg Stage, Overwintering and Oviposition 59 Eclosion Intervals 64 Dispersal of Newly Hatched Larvae 68 Factors Influencing the Spatial Distribution of Larvae 71 Number, Size and Duration of Larval Ins tars 78 Larval Feeding 85 Larval and Pupal Associates 92 Predator Studies 97 Parasite Studies 103 Drift 107 Pupae 120 Emergence and Adults 122 Dens ity 131 Mortality 145 Biomass 149 Page Growth 151 Growth and Temperature 162 Growth and Mortality 164 Production 165 Production Dynamics 166 Density, Biomass and Production Relationships 178 Production Comparisons between Streams, Species and Years 183 Indirect Methods of Calculating Production 190 The Hynes-Coleman Technique 192 Turnover Ratios 192 Drift and Production 193 Emergence and Production 194 Comparison of Simuliid Production with Other Aquatic Insects 197 Dynamics and Mortality of Black Fly Aggregates 198 The Function of Simuliidae in Oregon Stream Ecosystems 203 SUMMARY AND CONCLUSIONS 206 Species Composition and Life History 206 Population and Aggregate Dynamics 214 BIBLIOGRAPHY 221 APPENDICES Appendix I. Sample Statistical Analysis Calcula- tion for Pros imulium caudatum Larval Population at Station 0-II, 1972 237 Appendix II. Sample Calculation of Density and Biomass at Time I-1 239 Appendix III.Larval and Pupal Gastromermis Infection Densities and Percentages 241 Appendix IV.Original Weekly and Annual Drift Data for All Black Fly Species 246 Appendix V. Emergence at All 1971 and 1972 Stations for All Black Fly Species 256 Page Appendix VI.Larval Ins tar Production using Averaged 1971 and 1972 Density, Weight, Growth, Duration and Biomass Data 260 Appendix VII, Production Contribution Percentage for Black Fly Larvae, by Week 263 Appendix VIII, Original Weekly and Annual Growth, Biomass and Production for All Black Fly Species 264 Appendix IX,Initial Black Fly Larval Density per Square Meter of Usable Substrate at All 1971 and 1 972 Stations 292 Appendix X. Annual Black Fly Larval Production in Grams per Square Meter of Usable Substrate at All 1971 and 1972 Stations 295 LIST OF FIGURES Figure Page 1 Map showing all sampling stations on Berry, Oak and Soap Creeks. 20 2 Weekly range of water temperature at Berry Creek stations. 26 3 Discharge and weekly range of water tempera- ture at Oak Creek stations. 27 4 Discharge and weekly range of water tempera- ture at Soap Creek stations. 28 5 Devices used in laboratory experiments and field sampling. 36 6 Artificial stream trough at the Oak Creek Entomology Facility. 36 7 Diagram of stratified random sampling device. 37 8 The technique used in sampling black fly larvae during the study. 39 9 The sampling grid in position over a riffle. 39 10 Diagram showing typical Prosimulium spp. and Simulium spp. inhabited riffle situations. 56 11 Diagrammatic representation of Prosimulium spp., S. arcticum and S. canadense life cycles and dens ities. 60 12 Prosimulium caudatum larval head-capsule width measurements. 79 13 Simulium arcticum larval head-capsule width measurements. 80 14 Simulium canadense larval head-capsule width measurements. 81 Figure Page 15 Comparison of mean standing crop density and drift of P. caudatum and P. dicum larvae.