Use of Coarse Woody Debris by Diptera in Ozark Streams, Arkansas

Abstract

Aquatic dipterans were sampled from coarse woody debris (CWD) and stony benthic habitats from February 1991 through February 1992 in the White River, Illinois River, and Clear Creek of the Ozark Plateau in Arkansas. Chironomidae was the numerically dominant taxonomic group, and they were collected in significantly greater densities from CWD than from benthic habitats; but densities of other dipterans did not differ significantly between habitat types. Representatives of five taxa were collected in significantly greater densities from benthic habitats, and seven from CWD. The greatest estimated mean density of dipterans occurred during the spring, but differences were not significant because of high variation within seasons. The degree of decay of CWD was an important microhabitat factor for representatives of six taxa, of which four were xylophagous chironomids. The xylophages that were affected by degree of decay were Brillia flavifrons, Polypedilum fallax, Stenochironomus sp., and Xylotopus par. Eukiefferiella spp. and Phaenospectra sp. were the non-xylophages affected by decay stage. Biofilm volume appeared to be a less important factor in CWD use, but was important for representatives of two taxa (B. flavifrons and Eukiefferiella spp.).