Diel feeding activity of third and fourth instars of Anopheles quadrimaculatus Say were studied in a Michigan permanent pond. This field study examined the consumption of microbial and microinvertebrate food resources over a diel (24-h) period between two habitats (open water and vegetated areas). A fluorochromatic stain (4,6-diamidino-2-phenylindole) was used to quantify microbial dietary components within larval guts and habitats. Microbial analyses show that bacteria were the most abundant food type, followed by detritus, algae, and invertebrate parts/protozoans (IPP). Larval consumption of cladocerans was significantly greater at midnight than noon. Larval gut analyses examined every hour over a 24-h period provided significant evidence as to the approximate time larvae switch microinvertebrate dietary resources. Habitat had a significant effect on microinvertebrate consumption by An. quadrimaculatus larvae. Larvae consumed more water mites and rotifers in the open water areas than vegetated zones. We found that An. quadrimaculatus larvae do not preferentially feed on microinvertebrates over a diel period, however, larvae may feed selectively on rotifers in open water habitats. Knowledge of the “feeding area” or microhabitats, with respect to where and when larvae optimally forage as well as particle sizes and food types consumed in the natural habitats will enhance the success of bacteria and other particulate larvicides.