A revision of the bees of the genus Andrena of the Western Hemisphere

This work reports on a study of 1,200 specimens segregated into 9 species, 4 of which are new to science. One name is relegated to synonymy. The relationships within the subgenus and with other subgenera of Andrena are briefly discussed. The subgenus Hesperandrena was recognized and described by Timberlake in Lanham 1949 (p. 208) to include two previously described species, Andrena escondida Cockerell and Andrena baeriae Timberlake. These two species have in common a propodeum which, Timberlake described as having the dorsal surface, “... broad, gently curved and inclined from base to apex, without definite truncation, the lateral margins distinctly carinate and convexly arcuate.” This is the main character separating this subgenus (Fig. 4) from other subgenera of Andrena except that in the males of Hesperandrena the lateral margins of the propodeum are not carinate. Other characters are given in the description of the subgenus below. The species of this subgenus are very similar to one another and difficult to tell apart. The species are known only from California and Baja California. The reader is referred to earlier sections of this revision (LaBerge 1967, 1969, 1971, 1973, 1977, 1980, 1986, 1987, 1989; LaBerge and Bouseman 1970, 1987; LaBerge and Ribble 1972, 1975; Bouseman and LaBerge 1979; Thorp 1969; Donovan 1977) for details of morphology and a more complete bibliography on the genus Andrena. No new terms have been introduced and the bibliography presented here includes only references cited. Published locality and floral records are included in the sections at the end of each species account.