South American Leaf-Cutter Bees (Genus Megachile) Of The Subgenera Rhyssomegachile And Zonomegachile, With Two New Subgenera (Hymenoptera: Megachilidae) Author Gonzalez, Victor H. Undergraduate Biology Program and Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, Kansas Author Griswold, Terry USDA-ARS Pollinating Insects Research Unit, Utah State University, Logan, Utah Author Engel, Michael S. Division of Invertebrate Zoology, American Museum of Natural History, New York; Division of Entomology, Natural History Museum, and Department of Ecology & Evolutionary Biology, University of Kansas, Lawrence, Kansas text Bulletin of the American Museum of Natural History 2018 2018-11-02 2018 425 1 73 https://bioone.org/journals/bulletin-of-the-american-museum-of-natural-history/volume-2018/issue-425/00030090-425.1.1/South-American-Leaf-Cutter-Bees-Genus-Megachile-of-the-Subgenera/10.1206/00030090-425.1.1.full journal article 7630 10.1206/00030090-425.1.1 0cda6c92-3cdc-48ed-84a9-5627107d2823 0003-0090 4613364 Genus Megachile Latreille Aporiochile Gonzalez and Engel, new subgenus Figures 4B , 5D , 8–10 TYPE SPECIES: Megachile tricosa Cockerell, 1927 . DIAGNOSIS: This subgenus is known only from the male. It can be easily recognized by the following combination of features: preoccipital carina strong behind gena, mesotibial spur present and articulated to mesotibia, procoxal spine present, mesoscutum with spaced punctures, and T6 with preapical carina strong, broad, and medially emarginate. It resembles Austromegachile , Ptilosarus , and Rhyssomegachile in the strong preoccipital carina behind the gena. However, it can be separated easily by the procoxal spine (absent in Ptilosarus ), mesoscutal punctation (punctures contiguous or nearly so in Ptilosarus and Rhyssomegachile ), and shape of the preapical carina of T6 (weak and inconspicuous in Austromegachile , reduced to triangular denticles in Ptilosarus ). It superficially resembles the male of some species of Moureapis Raw in body size, punctation, presence of a procoxal spine, and shape of the preapical carina of T6. However, in Moureapis the preoccipital margin is rounded, the mandible is four-toothed with a basal process on its lower margin (mandible tridentate without basal process in Aporiochile ), and the mesotibial spur is absent (present in Aporiochile ). DESCRIPTION: Male : Moderate-sized bees (7.0–8.0 mm in body length). Integument smooth and shiny among spaced punctures (figs. 4B, 8A, B). Antennal flagellum unmodified, F1 shorter than F2; preoccipital border strongly carinate on gena only; mandible tridentate, without basal projection or tooth on lower margin; hypostomal area unmodified, without a projection or concavity. Procoxa with short (~ OD), blunt, apical spine; pro- and mesotibiae and tarsi unmodified; metafemur without a keirotrichial patch on posterosuperior surface; metabasitarsus elongate, about 3.9× longer than broad; mesotibial spur present, articulated to mesotibia, about as long as apical width of mesotibia. T6 swollen medially above strong, broad, medially emarginate preapical carina, without projections or spines on apical margin (fig. 8C); T7 not preapically projected into a spine or angle (fig. 9A, B); S5 and S6 with postgradular areas distinctly setose (fig. 9C, D); S4 exposed, with punctation and vestiture similar to those of preceding sterna; S8 without marginal setae (fig. 9E). Genital capsule elongate, flattened in lateral view; gonocoxite dorsally with distinct lobe (fig. 9F–H); gonostylus straight or nearly so in ventral view, broadest at midlength in lateral view, apically simple, unmodified, with long setae (about as long as width of gonostylus) along its medial margin; volsella present, apically rounded. Female : Unknown. FIGURE 8. Male holotype of Megachile ( Aporiochile ) tricosa Cockerell. A. Dorsal habitus. B. Lateral habitus. C. Dorsal view of T5 and T6. ETYMOLOGY: The new genus group name is a combination of aporia (Greek, meaning, “difficult” or “doubt”) and cheilos (Greek, “lip” or “rim”). Although the form of the name is technically a neuter plural, as is that of the genus Megachile , 2 the gen- der of the name is here considered to be feminine. DISTRIBUTION: Bolivia , Brazil , Peru (fig. 10). COMMENTS: Megachile tricosa , the type species of Aporiochile , was described from a single male specimen collected in northwestern Bolivia . It was synonymized under M. ( Rhyssomegachile ) urbana Smith ( Moure et al., 2007 ) , a species currently known only from the female holotype . However, 2 The generic name Megachile derives from Greek mega and chile , meaning “large lips” or “large rims”; because chile is a neuter (plural of ΧΕῖλoς) it should be treated as a masculine according to nomenclatural conventions, but in fact based on the application of feminine adjectives for specific names, it appears that authors have considered the genus feminine. We thus follow universal usage and consider Megachile and similar names derived from ΧΕῖλoς within Megachilini to be of feminine gender. both species are likely not conspecific judging by the smoother and shiner integument of M. tricosa , particularly on the mesoscutum (fig. 4B). In M. urbana the integument is dull and more coarsely punctate. In addition, M. tricosa does not share the diagnostic characters of Rhyssomegachile and our phylogenetic analysis does not suggest a close relationship to that subgenus (fig. 7). For example, M. tricosa has a short procoxal spine and sterna densely covered with fasciae, both features absent in the male of M. ( Rhyssomegachile ) simillima . In our analysis M. tricosa did not cluster with Rhyssomegachile and reanalyzing the data matrix using a terminal taxon that combined characters of both M. tricosa and M. urbana resulted in a large polytomy that included species from different subgenera (not shown). Thus, until sex associations or genetic evidence is available, we decided to place M. tricosa in its own subgenus, which is consistent with our present understanding of its relationships.