EMERGENCE OF CHIRONOMIDAE FROM SPRINGS IN THE CENTRAL HIGH-PLAINS REGION OF THE UNITED-STATES

Collections of chironomid pupal exuviae from 25 springs, springbrooks, and spring-fed streams in the central High Plains Region of the Unite d States were analyzed to determine taxonomic similarity and emergence patterns among springs. One hundred thirteen species in 70 genera and eight subfamilies/tribes were collected. Orthocladiinae was most spec ies rich (54 taxa) and abundant (55%), followed by Tanytarsini (23, 21 %), Chironomini (17, 8%), Tanypodinae (13, 6%), Diamesinae (2, 7%), Ps eudochironomini (1, 4%), Prodiamesinae (2, 0.1%), and Podonominae (1, 0.04%). Emergence species richness was low to moderate and species div ersity was low for individual springs when compared to richness and di versity of chironomids in streams of Kansas. Among the variables measu red in this study, spring type appears to influence species compositio n the greatest, with Orthocladiinae constituting a greater proportion of total taxa in rheocrene type springs and Chironominae being more ab undant in limnocrene springs and springs that are artificially altered into pool-like habitats. Species of Diamesinae, which often dominate streams at higher altitudes and latitudes and which are expected to oc cur near cold springs at lower altitudes and latitudes, were collected in greater numbers in larger spring-fed streams than in springs or sm all spring-runs, suggesting that discharge of groundwater into streams acts to shift community structure of Chironomidae toward that expecte d of a spring source habitat. Our results indicate that emergence of C hironomidae from springs in the High Plains is strongly influenced by the physical structure of the habitat, which in turn is a function of local geologic relief or artificial alteration.