Chelostoma (Neochelostoma), Engel & Griswold, 2019

Engel, Michael S. & Griswold, Terry, 2019, On the classification of North American Chelostoma (Hymenoptera: Megachilidae), Journal of Melittology 2019 (90), pp. 1-6 : 2

Neochelostoma Engel & Griswold, new subgenus

ZooBank: urn:lsid:zoobank.org:act:E0CD23F8-5FD1-40A1-B6C6-926B341E1445

TYPE SPECIES: Chelostoma californicum Cresson, 1878 ( Figs. 1, 2 ) .

DIAGNOSIS: The subgenus can be most readily distinguished in males from Foveosmia proper by the presence of apicolateral processes on the seventh tergum ( Fig. 5 ), in addition to the medial projections (sometimes joined apically to form a single projection; e.g., C. incisulum Michener ), and in females by the simple setae on the outer surface of the probasitarsus ( Fig. 3 ). In males of Foveosmia the lateral processes of the seventh tergum are lacking ( Fig. 6 ), while in females the setae on the outer surface of the probasitarsus are pectinately branched to plumose ( Fig. 4 ). Unlike species of Foveosmia which are oligoleges of Campanulaceae (Asterales) , this clade of New World species includes primarily specialists of Hydrophylloideae [ Boraginales : Boraginaceae : note that the most recent familial classification demotes Hydrophyllaceae within Boraginaceae ( APG, 2016) , but see Luebert et al. (2016) for an alternative arrangement] ( Hurd & Michener, 1955; Michener, 2007), although C. tetramerum Michener appears oligolectic on Amaryllidaceae ( Allium Linnaeus ) and C. minutum Crawford is polylectic with preference for Phacelia Juss. and Allium ( Sedivy et al., 2008) . Female visitation by C. minutum supports this preference; of 152 specimens in the Pollinating Insects Research Unit collection with floral records, Phacelia accounts for 35% and Allium for 29%. Each of the 14 other genera account for <10%.

ETYMOLOGY: The new subgeneric name is a combination of the Greek néos (νέος), meaning, “new”, and the generic name Chelostoma [itself formed in Greek of khēlḗ (Χηλή), meaning, “claw” and itself traditionally derived from khḗmē (Χήμη), meaning, “gape”, and stóma (στόμᾰ, genitive στόμᾰτος), meaning, “mouth”]. The gender of the name is neuter.

COMMENTS: In recent history this group of species has been treated as New World members of the subgenus Foveosmia ( Griswold & Michener, 1998; Michener, 2007), but is clearly distinct both morphologically and in terms of its floral associations, as well as phylogenetically ( Sedivy et al., 2008). The two Nearctic subgenera are allopatric; Neochelostoma is western, Prochelostoma eastern.

INCLUDED SPECIES: Aside from the type species ( C. californicum ), the following species are also included in Neochelostoma : C. bernardinum Michener , C. cockerelli Michener, C. incisulum Michener , C. marginatum Michener , C. minutum , C. phaceliae Michener , C. tetramerum . The keys of Michener (1938) and Hurd & Michener (1955) are sufficient to identify the described species of this subgenus.

Figures

Figures 1–2. Lateral habitus of female and male Chelostoma (Neochelostoma) californicum Cresson. 1. Female. 2. Male.

Figures 5–6. Male characters of Neochelostoma, new subgenus, and Foveosmia Warncke. 5. Seventh tergum of Chelostoma(Neochelostoma) tetramerum Michener, arrows indicate lateral projections. 6. Sev- enth tergum of C. (Foveosmia) distinctum (Stoeckhert).

Figures 3–4. Female characters of Neochelostoma, new subgenus, and Foveosmia Warncke. 3. Probasitarsus of Chelostoma (Neochelostoma) californicum Cresson. 4. Probasitarsus of C. (Foveosmia) campanularum (Kirby).