Freshwater ecosystems are under severe anthropic pressure (e.g. agriculture and mining), which generates adverse effects on the diversity of aquatic insects. We evaluated the insect community in streams impacted by agriculture and mining, and determined how these activities affected the community. We studied six streams in Caldas (Colombia), two with mining and two with agriculture impact. We collected the insects using a Surber net with three replicates per substrate (fine sediment, stones, and litter). In total, 12 502 aquatic insects were collected. The most representative genera were Baetodes, Simulium, and Cricotopus (57.7 %). Streams with agricultural activity had lower aquatic insects diversity than mining impact (F2,309 = 21.82, p = 0.001). The agriculture areas presented a structure dominated by Simulium and Cricotopus (Diptera, pollution-tolerant morphospecies). Baetodes dominated in stones substrate, Cricotopus in sediment, and Simulium and Cricotopus dominated in litter (F2,309 = 2.84, p = 0.001). Therefore, both factors (impact and substrate type) are being important in determining the diversity of aquatic insects. Our results suggested that agricultural activity has a higher impact on the diversity of aquatic insects, which may be associated with the loss of riparian vegetation.

Keywords: aquatic ecosystems, Colombian Andes, anthropic disturbance, benthic insects.