The life history of Isonychia sicca (Walsh) was elucidated from samples collected at Clear Creek from Oct. 1976-Jun. 1978, and Elm Fork of the Trinity River from Sept. 1977-Jun. 1978, Denton County, Texas. Adaptations for existence in an intermittent stream were of primary concern. Eggs are capable of diapausing through hot, dry summers and cold, wet or dry winters. Diapause is broken in the fall after rehydration and/or in the spring. I. sicca is usually bivoltine during a Sept.-Jul. wet period. Observations from Elm Fork indicate that emergence continues to Oct. if the stream remains permanent. Considerable overlap occurs between overwintering, spring, and summer populations.