Abstract
A new method of estimating the levels of infestation of black-fly larvae in streams is described. Hollow, metal cones, 20 cm high, 10 cm in diameter at the base, and painted white, were placed in infested streams. The cones were held in position with a wire attached to the apexes and fastened to an object in the stream or on the bank. The larvae attached to the cones in preference to stones or vegetation. Counts of those attached gave estimates of the levels of infestation in the streams, the periods when greatest numbers of larvae were moving downstream, and the fluctuations in number of larvae during the summer.
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