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75 Scrapers The functional group termed scrapers 1.ncludes thelse organisms morpho-behaviorally adapted for grazing upon surfaces with algae, periphyton, and other food adhering to it. The morphological adaptations range from the scoop shaped mandibles with a cut t ing e,dge of some Trichoptera, to the inner grinding surfaces of many msyfly mandibles and the rasping radular structure of gastropods. Scrapers: typically display body adaptations for maintaining their posItion on exposed feeding surfaces in rapidly flowing turbulent water such as dorsal-ventral flattening, ventral suction, etc. Because scrapers exhibit a wide range of morpho-behavioral adaptations related to mouth and body parts they have been separated into herbivore-grazing scrapers of mine,ral and organic surfaces and herbivore-piercers of cells and tissues and removal of fluids by suction. Therefore the dominant food type of the grazing scrapers is periphyton such as attached algae and associated material, and th"t of the scraper-piercers is living vascular hydrophyte cell and tissue fluids or filamentous algal cell fluids. In either case the general food particle size range is less than 1 mm. Dominant representatives of scrapers are found in the Ephemeroptera, Hemiptera (true bugs), Trichopera, Lepidoptera, Coleoptera, and some Neuroptera. Because the mode of feeding of scraper's is not qualitatively selective, the diet often includes particulate detritus and distinction between scrapers and collectors may be difficult. How'ever, true collectors are poorly adapted for removing algae from surfaces. Piercers The functional group termed piercers 1.11 a small group dominated by those organisms morpho-behaviorally adapted, for piercing living animal tissue. The group is essentially confined to species of microcaddisflies (Trichopera: Hydroptilidae). In contrast t,o the herbivorous scraper piercers, carnivorous piercers attack prey, pierc'e tissues and cells, and remove fluids by suction. Therefore the general particle size range of food is in excess of 1 mm. Additional members of piercers may be found in the Ephemeroptera and Megaloptera (Helgramites - alder flies, fish flies, and dotson flies). Predators (engulfers) The functional group termed predator or engulfer jl ncludes those aquatic organisms morpho-behaviorally adapted for consuming whole animals or parts in excess of 1 mm in size. The dominant food of these carnivores is living animal tissue and includes all those macroinvertebrates adapted for the capture of live prey. Dominant representatives of predators include members of the insect orders Collembola, Plecoptera, Hemiptera, Neuroptera, Lepidoptera, and Hymenoptera (bees). Although some members of the shredder, collector, and scraper functional groups ingest live prey (animals) in the course of their feeding, true predators are generally "restricted" to "engulfing" live prey. - .....IIIMl_-