Abstract
ABSTRACT This is only the second report of the life history, and first on ontogenic nymphal development, for any of the 22 western species of North American Sweltsa. Concurrent monthly collections of nymphs, with bi-weekly collections of adults from emergence traps, from an intermittent Oregon stream over 10 years yielded an interesting assemblage of stoneflies, including Sweltsa adamantea with no congeners. Adults were taken from emergence traps from 2001 to 2007, and the head-capsule widths of 1,159 nymphs from 1999 to 2007 collections were individually measured. Counts of antennal and cereal segments, windpad presence and backward projecting length, presence of dark, thoracic sternocoxal hairs ( a diagnostic character in late instar Sweltsa), diameter of compound eyes, general presence and length of body hairs, and sexual dimorphism were determined for 68 nymphs representing an array of 0.27 to 1.86mm head capsule widths from 2004 to 2007 collections. Eggs were studied and photographed with SEM. The li...
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