The Biology of Leptocerus aterrimus Steph. with Reference to its availability as a Food for Trout

Abstract

Observations on the feeding of brown trout, Salmo trutta L., from lakes have shown that larvae of Leptocerus aterrimus form an important part of the diet in May, June and July. Allen (1938), in a study of the food of trout from Windermere throughout the year, showed that Leptocerus larvae became the characteristic food in May, June and July, forming 15-1% by numbers of the diet in May, 37-1% in June and 36-2% in July. Humphries (1936) refers to the Leptocerus in Windermere as L. aterrimus. Frost & Smyly (1952), working at Three Dubs Tarn, showed that Leptocerus larvae featured to the greatest extent in the food of trout in May and were also a common constituent in June, July and August. Macan (1949) records L. aterrimus as representing the genus in this tarn. Mr T. A. Stuart (personal communication) showed that in Loch Moraig, Perthshire, L. aterrimus larvae were taken in large numbers during June (Table 1). The present investigations at Loch Dunmore, Perthshire, during 1954, indicated that the trout were eating the greatest numbers of L. aterrimus larvae in May.