A single specimen was collected one evening at Las Vegas, at a flower of Gaura coccinea. I then remarked of it: “Face narrower than type; possibly a distinct species.” It seemed strange that it should be visiting the Gaura, but it did not occur to me that I had a genuinely vespertine bee. On June 22, 1903, at Pecos, I was astonished to see a number of bees busily collecting pollen from the flowers of Galpinsia fendleri (a large yellow evening primrose)after sunset, at 7.30 p.m. I collected some, and found that they were my “Halictus amicus, var. a, ” which is evidently a distinct species. It is readily known from H. amicus by the narrower face and more sparsely punctured clypeus.