Abstract:
Between the fall of 1978 and the summer of 1980. the species composition of riffle beetles (Coleoptera: Elmidae) was determined in the Cottonwood-Neosho River drainage near Emporia. Kansas. Thirty-nine sample locations, which represents 23 different streams plus the Cottonwood and Neosho Rivers, were sampled for climes. Members of eight different elimds species were collected and identified from these locations. Since 1975, the State Biological Survey has reported that nine elmid species have been reported from the study area involved in this project. During the present study, the author collected a new species. Stenelmis sp., which has only been partially described by Alex Slater of the State Biological Survey. This new species was collected in Chase and Lyon Counties. which represents two new county records. It had previously been reported only from Bourbon and Johnson Counties in far eastern Kansas. Also. four other new county records were established for: Stenelmis crenata in Coffey County; Stenelmis decorata in Coffey County; Stenelmis vittipennis in Coffey County; and Microcylloepus pusillus in Lyon County. During my collections, differences became apparent between the numbers of S. bicarinata and S. sexlineata in the tributaries of the Cottonwood River and the Cottonwood River. Stenelmis bicarinata comprised approximately 75% of the total number of collected elmids in the Cottonwood River. While in the tributaries of the Cottonwood River, it comprised only 29% of the total number. Meanwhile S. sexlineata accounted for less than 5% of the total number of collected elmids in the Cottonwood River, but in the tributaries, it comprised 32% of the total. The reason for this is not clear, but could be due to the pollution tolerance of S. sexlineata, and Some interspecific competition between the two species.
