Food habits and dietary overlap of perlid stoneflies (Plecoptera) in a tributary of Lake Ontario

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Abstract
Food habit studies were conducted on the nymphs of 3 spp. of sympatric perlid stoneflies from May-Sept. 1979 in Orwell Brook, New York. A total of 1106 specimens were examined, which included 744 Phasganophora capitata, 251 Paragnetina immarginata and 111 Acroneuria abnormis. Chironomids, trichopterans and ephemeropterans were generally the principal prey of all 3 spp. [other prey included Hydracarina, Coleoptera, other Plecoptera and Tipulidae]. Using Horn''s measure of overlap, the monthly diets of P. immarginata and P. capitata were most similar (.hivin.X = 0.8006) and the diets of A. abnormis and P. immarginata (.hivin.X = 0.5595) least similar. Diel trends in food consumption during July indicated that the feeding intensity of both P. immarginata and P. capitata was the greatest from 2100-0500. Examination of the guts of P. immarginata and P. capitata at 4-h intervals over a 24-h period showed that there was considerable variation in the diel diet composition of these species.