Black flies in the boreal biome, key organisms in both terrestrial and aquatic environments: A review

Abstract

:The boreal biome is rich in running waters suitable for the development of black flies. Here we review the ecological roles of black flies and the options available for their management. Large numbers of these insects play quantitatively important roles in a number of processes, not only in the running-water habitats of the larvae but also in the terrestrial environments of the adults. Black flies suck blood from mammals, including humans, and from birds, with negative effects including occasional death of animals. Black flies also transmit parasites, including filarial worms and haemosporidians. In the last two decades, programs to control black flies by treating the larvae, using Bacillus thuringiensis var. israelensis, have been developed, with predominantly positive results but with limited understanding of the indirect impacts to the aquatic and terrestrial ecosystems. On a more positive side, adult black flies are food for a variety of predators and may favour pollination, as well as helping in nature conservation by deterring people from visiting wilderness areas. Black fly larvae feed on suspended particles, linking this energy source to invertebrate and vertebrate predators (e.g., salmonids). Because larval densities often are high, considerable amounts of sedimenting faecal pellets increase the local retention of organic material, and this provides nutrition for invertebrates and micro-organisms, and potentially fertilizes river margins. Larvae also produce silk, the role of which in the ecosystem is poorly known but potentially important.