Distribution and abundance of immature Tabanidae (Diptera) in a subarctic Labrador peatland

Abstract

During the summers of 1990 and 1991, 406 larval tabanids were extracted from samples of peat collected at eight sites in a subarctic Labrador peatland. Although not all larvae could be identified to species, five deer fly (Chrysops spp.) and six horse fly species (five Hybomitra spp., one Atylotus sp.) were identified. Chrysops probably zinzalus and Chrysops nigripes were the dominant deer fly species and Hybomitra arpadi was the most commonly collected horse fly. Deer fly larvae accounted for 88% of specimens collected. Chrysops larvae were collected most frequently from sites where the water table was at or below the substrate surface, and were rarely observed at sites where the substrate was submerged. The opposite was true for horse fly larvae, which were commonest at sites where the substrate was submerged. The density of tabanid larvae in the peatland was 14.04/m2 in regions of the fen where the water table was 3–5 cm below the substrate surface, 23.20/m2 in regions where the water table was at or slightly below the substrate surface, and 2.20/m2 in regions where the substrate was submerged. Tabanid pupae and pupal exuviae were collected from moss hummocks in the peatland.