. The Canadian field-naturalist. 190 The Canadian Field-Naturalist Vol. 114 1994 T3 0) o w n O c a> u. 100 80 60 40 20 0 1997 IIL T r M1 M2 M3 M4 JN1 JN2 JN3 JN4 JY1 JY2 JY3 JY4 Week Lone Males Pairs Lone Females [xx^ Broods Figure 1. Proportion of Harlequin Duck observations according to lone males, pairs, lone females, and broods for each week in the summers of 1994—1997. Months are abbreviated as M, JN, and JY for May, June, and July respectively. Blank cells represent weeks without survey data. developed from second to third instars in early May, from third to fourth instars in late Jun
. The Canadian field-naturalist. 190 The Canadian Field-Naturalist Vol. 114 1994 T3 0) o w n O c a> u. 100 80 60 40 20 0 1997 IIL T r M1 M2 M3 M4 JN1 JN2 JN3 JN4 JY1 JY2 JY3 JY4 Week Lone Males Pairs Lone Females [xx^ Broods Figure 1. Proportion of Harlequin Duck observations according to lone males, pairs, lone females, and broods for each week in the summers of 1994—1997. Months are abbreviated as M, JN, and JY for May, June, and July respectively. Blank cells represent weeks without survey data. developed from second to third instars in early May, from third to fourth instars in late June, and from fourth to fifth instars in mid to late July (Figure 3). The final (fifth) instars typically entered prepupation in late July, by sealing themselves to the underside of rocks. Following the flood in February 1996, instar transitions were 2-3 weeks later than in 1995 and 1997 (Figure 3). The majority of D. gilvipes from all years were found on bedrock (Table 3). Dicosmoecus gilvipes densities were significantly higher in 1995 than in either 1996 or 1997 following the flood (Table 4). There were no significant differ- ences among caddisfly instar densities within either 1995 or 1996; densities in 1997 declined steadily beginning with third instars (Figure 4). Annual den- sities of all benthic macroinvertebrates were not sig-. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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