Descriptions of the female, NYMPH, and variation in male characters of the stonefly Leuctra Szczytkoi (Plecoptera: Leuctridae)

Leuctra szczytkoi until recently was known only from the holotype male collected from Schoolhouse Springs of northcentral Louisiana. Collections in the late fall and winter of 1993-1995 provided additional specimens for describing the variation in the male characters and primary descriptions of the female and nymph of this species of the Leuctra ferruginea species group. Males are separated from all others in the group by a combination of a prominent subapical specillium spine, paraprocts and specillia being subequal, and by a triangular specillium. Females were distinguished by a shallow u-shaped notch on the subgenital plate. Nymphs apparently differ from others in the group by lacking sternal bristles anterior to segment 8. Leuctra szczytkoi is endemic to central and northcentral Louisiana in slow-flowing, lowland headwater streams of the Red River drainage.