Habitat ecology of Chironomid larvae of the Big Thicket streams

Typescript (photocopy).Chironomid larvae were collected from streams in the Big Thicket area of East Texas from November, 1981 to October, 1982. Primary stations were sampled monthly and secondary stations were sampled bi-annually. Samples of leaf debris, wood debris, and sediment were taken from each station and the chironomid larvae occupying the substrates were analyzed. A total of 15,112 individuals including 87 species were collected during this study. Four subfamilies of Chironomidae were represented in the collection. These included Tanypodinae (12 species), Diamesinae (2 species), Orthocladiinae (30 species), and Chironominae (43 species). Collections in this study yielded a larger number of individuals and species of chironomids than previous environmental studies in the Big Thicket. Twenty-two species are reported for the first time from Texas. The lowest number of individuals occupied the leaf debris with Rheotanytarsus sp. and Tanytarsus sp. 2 being dominant within that substrate. The wood debris, probably the most stable of the substrates, contained the highest number of species with Tanytarsus sp. 2 being the dominant species. The majority of individuals of chironomid larvae occurred in the sandy bottom where Lopescladius sp. was dominant. Tanytarsus sp. 1 occurred in over 65 percent of the samples. The populations of chironomid larvae were generally higher during the autumn. This was probably a result of the life cycle of chironomids and the effects of environmental factors. More younger instars occurred in the samples taken during the late summer and autumn collections. Also, water flow during the summer and autumn was low, providing a more stable environment, promoting chironomid population growth