84 
Psyche 
[March 
Larval Food i Habits . — The following food categories were identi- 
fied in the foreguts of larval fishflies from Hisey Fork: Isopoda, 
Diptera, Ephemeroptera, Megaloptera, and Trichoptera. Of the 
1 8 1 foreguts examined, 170 (93.9%) contained food and 11 (6.1%) 
were empty. The highest percentage of empty foreguts (8.9%) 
occurred in fall. 
Of the identifiable food materials, the isopod Asellus militaris 
(Hay) ranked first in percentage frequency of occurrence in all 
seasons. It ranged from 22.9 per cent in summer to 56.0 per cent 
in spring. The largest number (27) and the highest average (1.2) 
of isopods occurred in fall. 
Larvae of the caddisfly Cheumatopsyche sp. ranked second to iso- 
pods in percentage frequency of occurrence in summer (14.3), fall 
(19.7) and winter (18.0). Pupation and emergence could be re- 
sponsible for their lowest frequency (8.0%) in spring. In fall, the 
highest average (1.1) and greatest number (15) of larval caddisflies 
occurred in the diet of the fishfly. 
A limited number of mayfly naiads, Ephemerella coxalis McDun- 
nough, entered the diet in the spring and summer. The naiads ranked 
second (20.0%) to isopods in percentage frequency of occurrence in 
spring. 
Chironomid larvae were consumed in winter, where they occurred 
with a frequency of 10.3 per cent. They ranked behind isopods and 
caddisflies as a food source for larval fishflies. 
Some cannibalism was found in all seasons. It reached the highest 
frequency of occurrence ( 1 1.4%) in summer, where four N. fasciatus 
larvae were consumed. 
Digested and unidentified materials comprised a high percentage 
frequency of occurrence in fall (55.0), winter (46.1) and summer 
(51.4). In spring, they were found in 24 per cent of the foreguts. 
Minshall (1967) reported that larvae of N. fasciatus from Mor- 
gan’s Creek, a woodland springbrook in Meade County, Kentucky, 
consumed Gammarus, Asellus , Ectopria and unidentified amorphous 
materials. The guts of most larvae were partially full, and the con- 
sumed material was of indeterminate nature. 
Larval Development. — The larval population of N. fasciatus 
consisted of three size classes (Fig. 1). In the youngest size class 
(197 3, year of hatching), laboratory hatched larvae in June meas- 
ured 0.75 mm in head width (Fig. 2 and Table 1). The smallest 
larva in the stream measured 1.3 mm in head width and was col- 
lected in fall (29 November 1972). The method of collection pre- 
cluded getting large numbers of the youngest size class from the 
