Rearing black flies (Diptera: Simuliidae) in a closed system of water circulation.

A method of rearing large numbers of black flies has been devised using a closed system of water circulation. The subsystems used for hatching, feeding, filtration, and adult trapping are labor-efficient and sufficiently flexible to be useful for rearing most species of temperate and tropical black flies. The filtration subsystem permits a daily assessment of such parameters as larval growth rate, drift, and mortality so that life table statistics can be derived for populations of immatures. Four species of black flies, Simulium pictipes, S. vittatum, S. decorum, and Cnephia dacotensis, were used in developing this unique rearing system. Percentage survival varied with species and appeared to be a function of food quantity within discrete particle-size intervals. Over 28,000 larvae of C. dacotensis were reared in a single unit with 89.3% surviving to the adult stage. In each of two rearings of S. pictipes, conducted under different nutritional regimens, approximately 60% survived to the imaginal stage. Over 9,500 adults of S. vittatum were reared from 12,127 eggs. An F1 generation of S. decorum was produced from parental stock that originated as field-collected larvae. Combined survivorship of this species approached 94% with the production of 5,847 adults.