Abstract
Chironomus plumosus midge larvae were collected from Lake Winnebago, Wisconsin, for 10 weeks in the summer of 1985 and 10 weeks in the summer of 1986 in order to determine their bacterial floras. Altogether, 18 genera and 29 species of bacteria were found and identified. Some spirillum-like bacteria which were not isolated in culture were found by electron microscopy. Scanning electron micrographs of sectioned larvae revealed bacteria throughout the intestines. Gram-positive organisms were most prevalent in the larvae in the early part of the summer, and gram-negative organisms were most prevalent during the later part. Larvae accumulate bacteria within their intestines.