Mechanisms of fine particle capture by larval black flies (Diptera: Simuliidae)

Abstract

Larval black flies remove fine particulate matter from stream water using a mucosubstance which coats their filtering organs (cephalic fans). This mechanism, common among filter feeding marine invertebrates, but not previously reported in freshwater insects, explains how simuliids capture fine particles (0.091 – ca. 30 μm) which would otherwise escape the cephalic fans. Investigations of two theoretical filter feeding models revealed that direct interception is probably the predominant mode of fine particle filtration for black flies. The ability of simuliids to capture fine particles, which are abundant in many streams and often support a rich nutritive microflora, may account in part for their occurrence and success in diverse lotic habitats.