Larvae of Rhithrogena pellucida (Ephemeroptera:Heptageniidae) were observed feeding in observation flow cells using macroscopic video techniques. The stereotypic feeding behavior is described as cycles delineated by specific movements of the labial palps and consisting of stages of coordinated movement of the entire suite of mandibulate mouthparts. When employing the Labial Brushing Cycle, larvae used the labial palps to brush loosely accreted material from the substrate. When employing the Maxillary Scraping Cycle, larvae used special pectinate setae of the maxillary palps to remove material more tightly bound to the substrate. In both cycles, the legs of the larvae also removed material from the substrate. Larvae did not perform gathering cycles or feed on deposits of detritus. Food processing by successive fields of setae on various mouthparts to the point of ingestion is described in detail. Feeding observations combined with field and laboratory data on gut content and microhabitat distribution suggest that R. pellucida feeds primarily on periphyton. Comparisons are drawn between the primary scraping function of R. pellucida and the primary brushing function of Stenacron interpunctatum. A spectrum of adaptational strategies for obtaining food materials along a gradient of substrate association from seston to the most tightly attached materials is suggested and may be used to describe the feeding roles of many macroinvertebrates.
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McShaffrey et al. (1988) studied this question.