percentage frenquencv 
1976] Ashley, Tarter, & Watkins — Diploperla robusta 313 
BODY LENGTH , MILLIMETERS 
Figure 1 . Length-frequencies at monthly intervals for Diploperla robusta 
naiads from a small, woodland stream, Cabell County, West Virginia. The 
number of naiads collected each month is given in parentheses. 
