Bacteria associated with the ectoperitrophic space in the midgut of the larva of the midge xylotopus par (Diptera: chironomidae).

An ectoperitrophic association of bacteria with the midgut of Xylotopus par larvae was investigated by scanning electron microscopy and transmission electron microscopy. The bacteria attached to the epithelium as a well-defined band in the posterior midgut. They were morphotypically uniform and formed short filaments with endosporelike structures. The consistent presence and well-defined location of the bacteria in a region of the insect digestive tract usually void of microbes indicates a highly evolved symbiotic association, the nature of which is unknown at present.