LIFE-HISTORY AND SECONDARY PRODUCTION OF EPHORON-ALBUM (SAY) (EPHEMEROPTERA, POLYMITARCYIDAE) IN THE ILLINOIS RIVER, ARKANSAS

III the Ilinois River, the burrowing mayfly Ephoron album (Say) had a univoltine Life cycle with approximately an eight month egg diapause. Nymphs were first collected on 14 April, and the adults on 23 July, wi th peak emergence occurring between 27 July and 9 August. Linear regre ssion analysis showed a significant relationship between head capsule width and dry weight. Annual production estimates ranged from 5.92 to 6.70 g/m(2)/yr dry weight, and the cohort standing crop biomass was 8. 24 g/m(2). Cohort P/B ratios ranged from 7.19 to 8.13, and annual P/B ratios from 17.26 to 19.52. The cohort production interval was estimat ed at 126 days, based on field observations.