Larval distribution and succession of outlet-breeding blackflies (Diptera: Simuliidae) in New Hampshire

Abstract

Thirteen described species of outlet-breeding simuliids and five isomorphic sibling species of the Simulium venustum/verecundum complexes were collected in 1978 and 1979. Prosimulium fuscum, P. mixtum, Simulium aestivum, S. aureum, S. decorum; S. tuberosum, S. venustum (CC) and S. vernum were the most widely distributed species while S. aureum, S. decorum and S. venustum (CC) were the most abundant. Simulium decorum, S. tuberosum and S. venustum (AC(gB) and CC) were present at the same sites during both years while the remaining species varied in their occurrence at a specific site between the two years. Succession of Simulium spp. in late winter and spring was similar to that reported from other areas of northern North America. Most Simulium spp. studied were multivoltine while S. corbis, S. croxtoni and S. venustum (A/C) were univoltine. Simulium decorum had single or multiple generations, depending on the site. Larvae of S. venustum (A/C) and most species of the subgenus Eusimulium attached to trailing vegetation, while S. corbis, S. decorum, and S. tuberosum attached more frequently to submerged rocks and sticks. Prosimulium fontanum, S. gouldingi, S. venustum (CC and AC(gB)), and S. verecundum (A/C and ACD) did not demonstrate preference for a particular substrate. Reduction in stream flow affected the number of cohorts of S. aestivum and S. aureum and the number of generations per year of S. aureum and S. vernum.