Growth, respiration, and assimilation of blackfly larvae (Diptera: Simuliidae) in a lake-outlet in Finland.

A field experiment on feeding-rate in blackfly larvae (Diptera: Simuliidae) was conducted in the River Teuronjoki near its origin from Lake Pääjärvi, Finland. Small larvae were seen to feed more rapidly than large larvae.The increase in mean body-tissue weight of the larvae in Teuronjoki was determined and, from this relationship, growth-rate day for the larvae was obtained.In the laboratory, respiration-rate was determined for larvae of known body-tissue weight. Experiments were conducted when animals were feeding to replicate, as closely as possible, the conditions in the field. Respiration costs were higher for small, than for large, larvae.Estimates of assimilation-rate could be obtained by addition of growthrate and respiration-rate for larvae of given body-tissue weight. As the weight of material ingested per unit of time was known it was therefore possible to calculate assimilation efficiency. The values given in this study are the lowest yet recorded for freshwater detritivores.