The larval habitats and rearing of some common Chrysops species (Diptera: Tabanidae) in New Hampshire

About 1230 larvae and pupae of 10 early-season Chrysops species were collected and reared for 3 years in New Hampshire, the species most commonly taken being C. mitis O. S., C. ater Macq. and C. indus O. S. The most consistently favourable collecting sites were natural or artificial ponds, and the least favourable were rocky-bottomed streams. Permanent ponds with exposed loamy soils just above the waterline consistently supported large numbers of common Chrysops spp. Factors affecting collecting and rearing success were found to include synchronisation of prepupal and pupal stages and adult emergence, yearly variation in pupation and emergence time, amount and quality of lacustrine substrate for pupation, seasonal succession of species-cohorts or populations of different species in the same habitat, and abundance of a pteromalid parasite, Diglochis occidentalis (Ashm.), in the pupae. Yearly variation in the amount of favourable pupation substrate was the factor most directly affecting collecting success in any particular habitat, while parasitism by D. occidentalis most directly affected rearing success in the laboratory. The types of larval habitat for the 55 species of Chrysops known in North America are briefly discussed, and the species are listed under the 3 main habitat types: lentic, lotic and lentic-lotic.