Most previous work involving the diets of herbivorous macroinvertebrates has not examined the algal preferences of the herbivores compared to the availability of the food in the environment. Some diatoms adhere closely to the surfaces of substrates (low profile guild), while others grow on stalks (high profile guild), others belong to the motile guild, while still others are planktonic. Thus far, researchers have not closely examined whether herbivores have preferences among the guilds for food, for example, whether they prefer diatoms in the high profile because they are more readily accessible. We wanted to determine whether the diatom guilds differ among the streams, what environmental variables are correlated with these differences, and what effect these differences have on invertebrate feeding habits. We scraped 10 cm2 of biofilm from rocks (epilithon), and where possible, from dead wood (epidendron) and from living macrophytes (epiphyton) from reaches in three streams all located in the Huron River Watershed, but with unique catchments (urban, agricultural, and mixed). We then mounted, identified to genus, and counted the diatoms growing on the substrates from each stream (absolute abundance), and measured or otherwise obtained ten environmental variables (temperature, stream velocity, nitrate concentration, nitrite concentration, total phosphorus, total dissolved solids, conductivity, dissolved oxygen, pH, and percent impermeable surface) in the streams. Further, we used a D-net to collect macroinvertebrate larvae from the same reaches, identified them to family (Tipulidae (Diptera), Baetidae (Ephemeroptera), and Hydropsychidae (Trichoptera)), and then counted them. We then removed the foreguts from representative specimens of the herbivores, isolated and teased the gut contents of the specimens onto microscope slides, and counted the diatoms in the contents. We found significant differences in the taxonomic compositions of diatom communities in the streams, but no significant differences in Shannon-Weaver diversity among the streams/stream types. We did, however find significant differences in diatom guilds (high profile, low profile, motile, and planktonic) among the streams/stream types, and the high profile guild was the least dominant of the non-planktonic guilds in all streams/stream types. As expected, percent total impervious surface and conductivity were associated (but weakly) with the urban stream, but they were also about as weakly associated with the mixed stream. Despite these differences, however, the macroinvertebrate herbivores showed no consistent preferences in food selection. We conclude from this preliminary study that the guild status of benthic diatoms is irrelevant to the feeding habits of macroinvertebrates in these streams, irrespective of stream type or diatomic community.