Stomach content analyses of Simulium perflavum Roubaud 1906 (Diptera : Simuliidae) larvae from streams in Central Amazonia, Brazil

Stomach contents of Simulium perflavum Roubaud larvae were analyzed and com pared with plankton and periphyton collected in Jive streams, in Central Am azonia (Manaus and Presidente Figueiredo counties), in Sep./Oct. 1996 (dry season) and Feb./Mar. 1997 (rainy season). A total of 1,400 last-instar lar vae were dissected; the stomach contents were analyzed using different meth ods: fresh and after oxidation. A total of 87 taxa (algae, diatoms and roti fers) were found in the stomach contents. In each stream, qualitative sampl es of plankton and periphyton were collected; these were mounted between sl ides and cover slips. A total of 94 taxa of plankton and 54 taxa of periphy ton were collected. One species of Rotifera was present in the stomach cont ents, plankton and periphyton. Cluster analysis based on species compositio n of the organisms present in the stomach contents grouped the streams into two major groups, each belonging to a different drainage area. Correlation s based on presence/absence of species of microalgae in the stomach content s, plankton and periphyton indicated significant associations (p<0.05) betw een stomach contents and plankton and between plankton and periphyton (z te st), the Sorensen coefficient and cluster analysis corroborate the same ass ociations.