Many herbaceous grasses of the bambusoid alliance which are found in the ground layer of vegetation in the tropical American rain forest are visited by numerous insects at time of flowering. Insect collections were made on the inflorescences of two such genera, Olyra and Pariana, at localities in Brazil, Colombia, Panama, and Venezuela. A list of these insects is given with the species of grasses on which they were found. Two species of phorid flies (Phoridae) and two of gall midges (Cecidomyiidae) were observed only on plants of Pariana on which their life cycles may perhaps be spent. Because the grasses under discussion flower in a habitat where wind is negligible and cannot be assumed to play a major role in pollen transfer, the question arises as to whether insects are here the pollinating agents. If so, this result would represent a specialized type of pollination in the grass family which is generally considered to be strictly anemophilous.