18 
PAN-PACIFIC ENTOMOLOGIST 
trunk and one pair of lateral gills, each gill with a main trunk and two main 
branches; segment VII with one pair of gills, each gill with a main trunk and 
two major branches. Sterna of segments VIII and IX each with a pair of 
spine bearing plates (Fig. 17). Ninth tergum with a small lateral sclerite on 
each side. Anal proleg without spine-like setae on ventral surface (Figs. 16, 
17). 
Mature larvae up to 20 mm in length. 
Material examined .—Includes 225 adults, 76 of which were reared from 
pupae and 637 larvae. 
Disposition of material .—A series of adult and larval specimens of Hy¬ 
dropsyche separata will be deposited in the Royal Ontario Museum. The 
remainder of the specimens will be retained in the Entomology Museum of 
the Biology Department, University of Saskatchewan and in the author’s 
personal collection. 
Biology and Distribution 
H. separata in the Saskatchewan River system in Saskatchewan, Canada 
has a single generation per year with an extended emergence period. Pupae 
were collected from May 26 to August 1, adults from May 8 to August 24. 
The main emergence of adults occurs in June and July. Larval collections 
on any one date usually contain several different instars which is usual in 
aquatic insect species with broad adult emergence periods. Baumann and 
Winget (1975) found larvae of H. separata to be primarily herbivorous and 
detrivorous feeders. The gut contents of two larval specimens of this species 
from the Saskatchewan River system were found to contain primarily plant 
material. 
H. separata is widely distributed in northern North America from New 
York State west to British Columbia and Utah (various sources) and north 
to Great Slave Lake (Rawson, 1953). Baumann and Winget (1975) collected 
H. separata from the turbid waters of the relatively large White River in 
Utah. In Saskatchewan H. separata is abundant in larger turbid rivers such 
as the Saskatchewan, South Saskatchewan, North Saskatchewan and Battle 
Rivers. This species does not occur in the clear, often rapid streams of the 
boreal forest region of Saskatchewan. In the South Saskatchewan River the 
Diefenbaker Lake reservoir not only alters the seasonal temperature regime 
of the river downstream from it (Lehmkuhl, 1972) but it also acts as a trap 
for suspended matter which is brought into the reservoir by the turbid waters 
of the South Saskatchewan River. The water which leaves the reservoir is 
relatively free of suspended matter. Lehmkuhl (1972) suggested that aquatic 
insects are eliminated directly downstream from the Diefenbaker Lake res¬ 
ervoir because the annual temperature cycle of the river is altered. Further 
downstream, a gradual recovery of the insect fauna occurs and at Saska- 
