82 
Psyche 
[March 
divided into four seasons; fall (Sept.-Nov.), winter (Dec.-Feb.), 
spring (Mar.-May), and summer (June-Aug.). Usually a single 
collection was made during the middle month of each season. Larval 
fishflies were collected from under rocks (8-50 cm in diam) and in 
logs throughout Hisey Fork by handpicking with forceps. Generally, 
the larvae occurred about 1 per 20-30 meters of stream length. They 
were placed in boiling water to prevent shrinkage and stored in 70 
per cent ethanol. 
Size-frequency distributions of head widths, arranged in 0.2 mm 
groups, were employed each season to determine the size classes of 
N. fasciatus larvae. Also, 21 1 larval head widths, measured with a 
dial vernier caliper (nearest O.i mm), were used as an index of 
growth. 
Data regarding larval food habits were determined by foregut 
analysis. The foreguts were excised and the contents sorted into 
various taxonomic categories under a dissecting microscope. The 
number of specimens in each taxon was counted and recorded for 
each foregut. The following calculations were made seasonally: 
( 1 ) the percentage of foreguts in which a particular taxon occurred 
(percentage frequency of occurrence) and (2) the average number of 
specimens in all foreguts containing that particular taxon. 
Fecundity in the adult hshfly N. fasciatus was determined by 
direct counts of ovarian eggs. Both ovaries of 10 adults were re- 
moved and a total of 6802 eggs were counted. The regression of 
fecundity on total length was calculated and a coefficient of correla- 
tion determined. 
Water temperature was measured with a thermometer placed near 
the bottom. Determinations of total alkalinity, total hardness as 
CaC 0 3 and pH were carried out in the laboratory with a Hach 
chemical kit, Model DR-EL. Dissolved oxygen concentration was 
measured in the field with a Hach chemical kit, Model AL-36-WR. 
Results and Discussion 
Stream Environment. — During the study period, water tempera- 
ture ranged from 5.6 to 18.3 C, winter and summer, respectively. 
The average pH value was 7.7 (range, 7.0-8.0). The waters usually 
were supersaturated with dissolved oxygen which ranged from 9 to 
13 m g/l (x = 11 mg/ 1 ). Total alkalinity concentrations ranged 
from 45 to 85 mg/l, winter and summer, respectively (x = 68 
mg/l). The average total hardness concentration was 163 mg/l; 
the range was 120 (spring) to 210 (summer) mg/l. 
