214 
Psyche 
[June-September 
Food Habits. — This population of S. itasca was found to feed 
almost exclusively on the ostracod, Cyclocypris sp. The only other 
food items were 3 midges, Chironomus sp., which were found on 3 
different occasions. Of the 84 foreguts analyzed, 21 percent were 
empty and 79 percent contained food. Ostrocods were found in 71 
percent of the foreguts, and midges were found in 4 percent of the 
foreguts. 
Excluding the month of August when a very small sample size (4) 
was used, the largest number of empty foreguts occurred in January 
(50%). The percent of empty foreguts increased again in April 
supporting the findings of Woodrum and Tarter (1973) in S. 
aequalis that the larvae probably do not feed just before pupation. 
Azam and Anderson (1969) reported S. rotunda and S. Cali- 
fornia to be indiscriminate feeders and reported cannibalism to be 
frequent. Woodrum and Tarter (1973) found S. aequalis to be more 
restricted in its feeding due to the limited choices of organisms 
found in the acid mine stream in which they were located. They also 
reported cannibalism to occur to a lesser extent. The S. itasca in this 
investigation were found to be more restrictive feeders preying 
almost exclusively on ostracods while having an abundant supply of 
other organisms upon which they could feed. Cannibalism was 
observed in the laboratory when larvae were confined for three days 
without food. 
Predation. — The stomachs of 18 odonates and 10 sunfish were 
examined. No alderfly remains were found in the sunfish and only 
one alderfly head was found in the odonates. Schwiebert (1973) 
noted that the hellgrammite and trout are predators of the alderfly. 
pH Tolerance. — The 96 hour TL™ value for S. itasca was found 
to be 3.1. All ten larvae survived the 96-hour period at pH values of 
7.0 and 5.5, 70 percent survived in a pH of 4.0, and 30 percent 
survived at a pH of 2.5. Tarter and Woodrum (1972) found S. 
aequalis from an acid mine stream to have a TLm value of 2.1. These 
values would indicate that S. itasca and S. aequalis are quite 
tolerant of low pH. Sialis spp. have been noted to be tolerant to low 
pH conditions in western Pennsylvania streams (Roback and 
Richardson, 1969), Roaring Creek in eastern West Virginia (Warner, 
1971), and in the East Fork of the Obey River in Tennessee (Nichols 
and Bulow, 1973). 
