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<br />74 <br /> <br />mining, and boring. Dominant foods include living and decomposing vascular <br />hydrophyte plant tissue and coarse particula,te organic matter. The general <br />particle size range of foc.d consumed is in I~Xcess of 1 mm (103 microns). <br />The group includes both herbivores (chewers and miners) and detritivores <br />(chewers and wood borers). Dominant repres,~ntatives of shredders are found <br />in the insect orders Plecoptera (stoneflies), Trichoptera (caddis flies), <br />Coleoptera (beetles), Diptera (true flies) and some in the Lepidoptera <br />(butterflies) . <br /> <br />Shredders are known to selectively feed on leaf substrates maximally <br />colonized with the fungus, hyphomycete mycelia (Triska 1970, Barlaocker and <br />Kendrick 1973a, 1973b, 1975). The aquatic .hyphomycete,;:, have a simple life <br />cycle with a short generation time, can degrade cellulose, and in some <br />species lignin, and can use either inorganic or organic nitrogen. <br />Shredders usually prefer CPO~ well colonized by fungi and microorganisms <br />and have been shown to select for the most microbially colonized and <br />conditioned material. This preference is reflected in high rates of <br />consumption, efficiency of converting food to growth and growth rate <br />(Cum:nins and Klug 1979). Food preferences suggest that the microJial <br />biomass and especially fungi are nutritionally important to the shredders. <br />The shredders either directly assimilate (absorb) the digested microbial <br />biomass or utilize substrate partially transformed by :the organisms. <br />Shredders which lack the enzyme cellulase actually dep'~nd on the <br />microbial-fungal process to "predigest" plant and woody detrital <br />fractions. Therefore, shredders feeding on nutritionally incomplete CPOM <br />derive their nutritional requirements from :lngested microorganisms and <br />partially digested detritus. <br /> <br />Collectors <br /> <br />The functional group called collectors includes itnmature and adult <br />stages of aquatic insects that occur in water and are morphologically <br />adapted for gathering, filtering, and feeding on suspensions and surface <br />film. The dominant food type consumed i.s decomposing fine particulate <br />organic matter (FPOM). The general particle size rangE! of food consumed is <br />less than 1 mm 003 microns). The group has been divided into detritivores <br />- filterers or suspension feeders, and detritivores adapted for gathering <br />or deposit (sediment) feeding including surface film fE!eders. Dominant <br />representatives of collectors are found in the insect orders Ephemeroptera <br />(mayflies), Trichoptera, Lepidoptera, Coleoptera, Dipt.!ra and Collembola. <br /> <br />Whereas shredders feed selectively on the basis of food quality (and <br />quality is a function of the extent of microbiota colonization), the <br />collectors ingest food on the basis of particle size alone (Cummins 1975). <br />Collectors exhibit a wide range of morpho-beha~ioral adaptations for <br />acquiring fine particle detritus and the separation of collectors into <br />filtering and gathering groups is intended t.o distingui.sh between those <br />collectors feeding on fine and ultrafine particulate organic matter in <br />transport or suspension, from those feeding on depositE,d, sediment related <br />detritus. <br /> <br />.----. <br />- <br />