24. Larvae of the Caddisfly Hydropsyahe 43 



25. An adult of the genus Hydropsyahe 43 



26. Aquatic invertebrates of the Yellowstone River 44 



27. Emergence of mayflies from the Yellowstone 



River, 1974-76 48 



28. Adult Mayfly (Traverella albertana) 48 



29. Adult Mayfly (Trioorythodes minutus) 49 



30. Emergence of stoneflies from the Yellowstone 



River, 1974-76 49 



31. Adult stonefly (Isoperla longiseta) 50 



32. Emergence of caddisflies from the Yellowstone 



River, 1974-76 51 



33. Population estimates for August 1975, mean and range of six 



Water's samples at each station 53 



34. Population estimates for September 1975, mean and range of six 

 Water's samples at each station 54 



35. Population estimates for October 1975, mean and range of six 



Water's samples at each station 55 



36. Population estimates for November 1975, mean and range of six 



Water's samples at each station 56 



37. Mean percentage composition of invertebrate orders from Water's 

 samples taken August-November 1975 57 



38. Species diversity: range of six Water's samples and all six 



pooled, August 1975 60 



39. Species diversity: range of six Water's samples and all six 



pooled, September 1975 61 



40. Species diversity: range of six Water's samples and all six 



pooled, October 1975 62 



41. Species diversity: range of six Water's samples and all six 



pooled, November 1975 63 



42. Seasonal changes in Shannon-Weaver diversity indices 



64 



43. Proposed relationships between invertebrates and the factors 



that determine their distribution and abundance 68 



VI 



