54 
Psyche 
[March 
Materials and Methods 
Beech Fork in Wayne County, West Virginia, is the study area. It 
is 45.9 km long and drains moderate to steep slopes of mesophytic 
hardwood forest. It originates at an elevation of approximately 343 
m and flows northwesterly to enter Twelvepole Creek at an eleva¬ 
tion of 165 m near Lavalette, West Virginia. The average gradient is 
3.9 m/km. The study site is located at 38°18'57" N latitude and 
82°25'22" W longitude, and is 3.7 km above the mouth of Beech 
Fork. It is a slow to medium speed riffle 55 m long that averages 5.2 
m in width and 25.4 cm in depth. The substrate consists of large 
rocks and stones, and a mixture of gravel, sand, and silt. The more 
dominant species of the riparian forest are Boxelder Acer negundo 
L., Silver Maple A. saccharinum L., Black Walnut Juglans nigra L., 
Sycamore Platanus occidentalis L., and Slippery Elm Ulmus rubra 
Muhl. 
Monthly sampling for Baetisca bajkovi nymphs began in June 
1976 and continued through May 1977. Sampling was accomplished 
by starting at the lower end of the riffle and working upstream using 
a long handled bottom dredge with a fine mesh net (60 threads per 
inch). The dredge was raked along the bottom while the substrate 
was disturbed and loosened upstream allowing the organisms to 
drift into the net. The nymphs were immediately preserved in 70 
percent ethanol. 
Water temperature was measured each month with a mercury 
thermometer. The thermometer was placed in the riffle at a depth of 
approximately 5 cm. Determinations of dissolved oxygen concen¬ 
tration, bicarbonate alkalinity, and total hardness were carried out 
with a Hach chemical kit. Model AL-36-WR. The pH was meas¬ 
ured with a Corning Model 5 pH meter. The oxygen saturation 
values were obtained using Rawson’s nomogram (Welch, 1948). 
Length-frequency distributions were recorded for the nymphs to 
help determine the duration of the life cycle. Histograms were 
arranged in 1 mm size groups for each month with the males and 
females combined. The body length of the nymphs, from the 
anterior-most tip of the head to the base of the caudal filaments, was 
measured with a dial Vernier caliper under a dissecting microscope 
to the nearest 0.1 mm. Head width measurements were used to show 
the monthly index of growth. The head widths (including eyes) were 
measured to the nearest 0.01 mm with an ocular micrometer in a 
Bausch and Lomb dissecting microscope. A population range dia- 
