Assimilation rates of different particulate foods for Simulium verecundum (Diptera: Simuliidae).

Particulate food assimilation rates for larvae of Simulium verecundum Stone & Jamnback were studied using three radiolabelled particulate foods: Navicula pelliculosa Bréb. ex Kütz.) Hilse (a diatom), Scenedesmus quadricauda (Turp.) Bréb. (a green alga), and field-collected, size-fractionated (< 3.0 microns) heterotrophic bacterioplankton. Assimilation was determined by radiolabelling the microorganisms followed by a 5-h laboratory feeding of each food to fifth- to seventh-instar S. verecundum. The bacterioplankton provided the highest assimilation efficiency (27.8%). N. pelliculosa produced higher assimilation efficiency estimates (19.5%) than did S. quadricauda (4.0%). The relationship between black fly abundance and the availability of quickly assimilated food is discussed.