Dianthidium singulare (Cresson, 1879)

Anthidium singulare Cresson, 1879: 207 [♀].

     Holotype ♀. USA, Nevada, by Morrison [ANSP no. 2400].

Dianthidium singulare var. perluteum Cockerell and Cockerell, 1904, in Cockerell, 1904: 23 [♀]. Synonymy by Grigarick and Stange (1968: 54).

     Syntypes ♀. USA, California, Wilson’s Peak and Strawberry Valley, by Dr. Davidson [AMNH].

Dianthidium singulare melanognathum Cockerell, 1925: 363 [♀]. Synonymy by Grigarick and Stange (1968: 54).

     Holotype ♀. USA, California, Fresno County, Huntington Lake, at 7000 ft., 7 July 1919, by E.P. Van Duzee [CAS no. 1745].

Taxonomic notes: Cockerell (1904: 23) was the first to recognize Anthidium singulare Cresson, 1879 as a Dianthidium Cockerell, 1900.

The ♂ of Dianthidium singulare perluteum Cockerell and Cockerell, 1904 was briefly described by Cockerell (1925: 363) and Michener (1935: 23); Timberlake (1943: 75) provided a bried description of the ♂ of D. singulare (Cresson, 1879).

Cockerell (1925: 363), Michener (1935: 23) and Timberlake (1943) recognized Dianthidium singulare perluteum Cockerell and Cockerell, 1904, as a valid subspecies, though in his revision, Timberlake (1943) did not include Dianthidium singulare melanognathum Cockerell, 1925 as a synonym or valid taxon. Michener (1951: 1145) recognized all three taxa as subspecies, but Grigarick and Stange (1968: 54) subsequently treated them as conspecific.

Timberlake (1943: 75) incorrectly attributed D. singulare perluteum to T.D.A. Cockerell only, who was listed as the sole author of the paper (Cockerell 1904: 23), though both he and Wilmatte Cockerell are included with the original description (see Cockerell 1925: 363; Michener 1935: 23; Grigarick and Stange 1968: 54).

Though Grigarick and Stange (1968: 54) indicate the holotype of Dianthidium singulare var. perluteum Cockerell and Cockerell, 1904 was collected at Wilson's Peak, Strawberry Valley, California, Cockerell (1904: 23) clearly indicated that these represented two separate specimens collected at two locations in California, thus represent two syntypes.

DNA Barcode Index Number (BIN): BOLD:ADG3397

Diagnosis: Both sexes of D. singulare can be distinguished from all other Dianthidium in Canada by the large body size (> 12mm) and terga 2-5 with inflated lateral portions. In addition, both sexes possess metacoxae with a very large, elongate pale spines on outer surfaces; both sexes of D. curvatum also have spines, though these are much smaller (i.e., spine about as long as its basal width). The females can be further distinguished from other species by the combination of mandible without a distinct preapical tooth (shared only with Dianthidium plenum and D. pudicum), and apical terga and sterna with apical margins broadly truncate.

Biology: Michener (1935: 24) indicated that the nest of D. singulare perluteum consists of a single 2 by 2.5 cm cell of pebbles cemented to the face of a large boulder, the pebbles used 1 to 4 mm in diameter, and described the cocoon. Grigarick and Stange (1968: 54) provided additional details.

Distribution in Canada: Sheffield and Heron 2019 [BC].