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 fo ods: Navicula pelliculosa Breb. ex Kutz.) Hilse (a diatom), Scenedesmu s quadricauda (Turp.) Breb. (a green alga), and field-collected, size- fractionated (<3.0 mum) heterotrophic bacterioplankton. Assimilation w as determined by radiolabelling the microorganisms followed by a 5-h l aboratory feeding of each food to fifth- to seventh-instar S. verecund um. The bacterioplankton provided the highest assimilation efficiency (27.8%). N. pelliculosa produced higher assimilation efficiency estima tes (19.5%) than did S. quadricauda (4.0%). The relationship between b lack fly abundance and the availability of quickly assimilated food is discussed.