Cremnomegachile Gonzalez & Engel, 2019

Gonzalez, Victor H., Gustafson, Grey T. & Engel, Michael S., 2019, Morphological phylogeny of Megachilini and the evolution of leaf-cutter behavior in bees (Hymenoptera: Megachilidae), Journal of Melittology 2019 (85), pp. 1-123 : 58-60

Cremnomegachile Gonzalez & Engel , new genus

ZooBank: urn:lsid:zoobank.org:act:9B13591A-A7C6-4781-AF42-4B131460E1B5

( Fig. 16 )

TYPE SPECIES: Megachile dolichosoma Benoist, 1962 .

DIAGNOSIS: This genus resembles Stenomegachile in the elongate, shiny female mandible ( Fig. 16A ), female hypostomal area toothed, and male preapical carina of T6 bilobed ( Fig. 16E ). It can easily be separated by the shape of the mesoscutum, which is midanteriorly projected and truncate, thus forming an anterior-facing area ( Fig. 16B ).

DESCRIPTION: Small to moderate sized-bees (10.0–12.0 mm in body length). Integument shiny, with punctures coarse and spaced. Preoccipital border strongly carinate on gena; ocelloccipital distance distinctly greater than ocellocular distance.

♀: Mandible without interdental laminae, elongate, outer surface shiny, with apex about as broad as base, four-toothed, Mt 4 on upper margin and clearly separated from Mt 1–3, which are on distal margin; clypeus not covering base of labrum; labrum elongate, triangular, with distinct preapical protuberance bearing long, stiff tuft of setae; hypostomal carina with posterior portion ending in a tooth. Pronotal lobe with transverse lamella; mesoscutum flat on disc, midanteriorly projected and truncate, thus forming an anterior-facing area; mesoscutellum flat, not overhanging metanotum in dorsal view ( Fig. 4C ). Metasoma narrow, parallel-sided, with white apical fasciae and distinct postgradular grooves on T2–T4; sterna without apical fasciae beneath scopa; T6 straight (vertical) in profile.

♂: Antennal flagellum unmodified, F1 shorter than F2; mandible tridentate, without basal projection or tooth on lower margin; hypostomal carina unmodified, area behind mandible unmodified, without a projection or concavity; procoxa aspinose; pro- and mesotibiae and tarsi unmodified; metabasitarsus elongate, about 4.0× longer than broad; mesotibial spur present, articulated to mesotibia, about as long as apical width of mesotibia. T6 vertical in profile, with deep concavity above broad, medially emarginate preapical carina, distal margin without a distinct tooth or projection; T7 with preapical carina broadly rounded; S4 exposed, with punctation and vestiture similar to those of preceding sterna; S8 with marginal setae. Genital capsule elongate, 1.9× longer than wide; gonostylus straight or nearly so in ventral view, apically simple (not bifid), much narrower than base in lateral view, with long setae along its medial margin; volsella present, apically truncate.

ETYMOLOGY: The new genus-group name is a combination of of the Greek word, kremnos, meaning “overhanging wall”, in reference to the projected and anterior-facing surface of the mesoscutum, and the generic name Megachile . The gender of the name is feminine [as noted by Gonzalez et al. (2018: p. 19), although Megachile is a neuter pleural and should be nomenclaturally considered masculine, precedence is to consider names based on chile (ΧΕῖλος), meaning, “lip” or “rim”, to be feminine].

COMMENTS: The genus is known from the type species only, which occurs in southern Madagascar ( Pauly et al., 2001). This results in the new combination, Cremnomegachile dolichosoma (Benoist) .

In addition to the features indicated in the diagnosis, the male of Stenomegachile differs from that of Cremnomegachile in the four-toothed mandible (tridentate in Cremnomegachile ); the hypostomal area, behind the mandible, which is strongly projected into a tooth (unmodified in Cremnomegachile ); and the pro- and mesotarsi that are expanded (normal in Cremnomegachile ). The genital morphology is quite different, particularly in the shape of the volsella, which is narrow and apically notched (vide Pasteels, 1965: p. 513). In the female of Stenomegachile the mandible is more elongate and apically curved, and the labrum is long but parallel-sided. The hypostomal projection of Stenomegachile might not be homologous to the hypostomal tooth of Cremnomegachile because it is not part of the posterior portion of the hypostomal carina as in the latter genus.

Figures

Figure 4. Some female morphological features used in the phylogenetic analysis. A, B. Lateral view of axilla. C. Dorsal view of mesoscutellum and metanotum. D, E. Outer view of apex of mesotibia. F–I. Pretarsal claws. Megachile (Melanosarus) xylocopoides Smith (A); M. (Stenomegachile) dolichosoma Benoist (B, C); M. (Chelostomoides) rugifrons (Smith) (D); M. (Megachiloides) pascoensis Mitchell (E); Dioxys productus (Cresson) (F); M. (Acentron) albitarsis Cresson (G); M. (Hackeriapis) ferox Smith (H); M. (Schizomegachile) monstrosa Smith (I).

Figure 16. Cremnomegachile dolichosoma (Benoist), new combination. A. Facial view of female. B. Detail of female mesoscutum. C. Female metasoma in dorsal view. D. Lateral view of female. E. Male terminal terga. F. Lateral view of male.