66 David R. Lenat 



At the group level, taxa richness varies considerably across the 

 three types of streams. Each stream type has a different assemblage of 

 invertebrate predators. Plecoptera and Trichoptera are most diverse in 

 Mountain streams, Megaloptera in Piedmont streams, and Odonata in 

 Coastal Plain streams. The "other" category, also most important in 

 Coastal Plain streams, includes many other predators: Hirudinea, Tur- 

 bellaria, and Prostoma graecens (Bohmig). Shifts may also be observed 

 in the collector-gatherer groups. Going from the mountains toward the 

 coast, Ephemeroptera-Trichoptera decline and are replaced by Coleop- 

 tera (Piedmont only), Oligochaeta, Crustacea, and Mollusca. 



Table 5 shows density (expressed as a percentage of total density) 

 for Cane Creek and five other North Carolina Piedmont streams. The 

 density values show much greater between-stream variability than does 

 average taxa richness. These data may serve as controls only if used 

 with extreme caution. Variability is imposed by such factors as stream 

 size, substrate, and geographic locality. The data are further biased by 

 the selection of riffle areas and by the mesh size used in sample process- 

 ing. A smaller mesh size will increase the importance of Diptera and 

 Oligochaeta. 



Table 5. Density by group (as percent of total density) for Cane Creek and 

 other unstressed North Carolina Piedmont streams. Data are the aver- 

 age of 3-4 collections, rounded to integer value. 



Stream: 



Cane 



Bolin 



Gates 



UT Lanes Long Br. 



4-Mile 



Group 















EPHEMEROPTERA 



13 



12 



16 



6 



27 



38 



PLECOPTERA 



3 



5 



9 



3 



4 



14 



ODONATA 



- 



- 



1 



- 



1 



1 



TRICHOPTERA 



50 



70 



3 



14 



25 



10 



COLEOPTERA 



5 



3 



4 



29 



2 



9 



MEGALOPTERA 



2 



1 



1 



- 



- 



- 



DIPTERA 



20 



8 



61 



45 



39 



27 



MOLLUSCA 



3 



- 



- 



2 



- 



- 



OLIGOCHAETA 



2 



- 



2 



1 



1 



- 



CRUSTACEA 



- 



1 



2 



- 



- 



1 



OTHER 



2 



- 



1 



- 



- 



- 



ACKNOWLEDGMENTS.— I would particularly like to acknowl- 

 edge the help and support of two colleagues: Samuel Mozley, N.C. 

 State University, and David Penrose, N.C. Division of Environmental 

 Management. Taxonomic assistance was received from many sources: 

 Chironomidae — Samuel Mozley; Patrick Hudson, U.S. Fish and Wild- 

 life Service; Leonard Ferrington, University of Pittsburgh; Robert Bode, 



