Phenology of the Larval Chironomidae of Large Temperate Nearctic River

David C. Beckett, University of Southern Mississippi


I used rock-basket and multiplate samplers to collect chironomid larvae on ten sampling dates throughout 1979 from the Ohio River, a large river with a wide yearly temperature range (DELTAT = 29-degrees-C in 1979). Winter and early spring collections of chironomids were heavily dominated by species of the subfamily Orthocladiinae such as Eukiefferiella brevicalcar gr. , Hydrobaenus pilipes, Orthocladius obumbrateu, Orthocladius oliveri, Orthocladius sp., and Parakiefferiella sp. Although these six species dominated cold-weather collections, no individuals of any of these species were present in the samples in the warm months of July and August. Such species probably aestivate in the summer as eggs or early larval instars. The summer fauna was dominated, instead, by species of the subfamily Chironominae, such as Rheotanytarsus sp., Stenochironomus sp., and Polypedilum convictum. This study shows that the pattern of changing dominance (Orthocladiinae/Chironominae) can apply not only latitudinally and altitudinally, as shown by other investigators, but also seasonally in a single temperate location. The utilization of the Ohio River's wide annual temperature range by the Chironomidae, with each species selecting the appropriate season and temperature for its development, results in a diverse community when viewed over the entire year, and in large dissimilarities in composition between the summer and winter faunas.