In the same leaves of Populus angustifolia in which were found the tenthredinid (lepidopterous?) leaf-miners,* in the Canada Alamosa, northern Sierra county, N. Mex., in June, 1892, there were also found speciemns of a very distinct leaf-miner. It bears of striking resemblance to the leafminer of the vine found in the Mesilla valley of the Rio Grande. It possesses the sucker-like mouth of that miner. After being mounted in glycerine on a slide for several days, however, the outer portion of the distended sucker-like organ became transparent, exposing within what appear to be two stout rounded mandibles with teeth on their inner edges.