Megachile (Litomegachile) brevis Say, 1837

Bzdyk, Emily L., 2012, A revision of the Megachile subgenus Litomegachile Mitchell with an illustrated key and description of a new species (Hymenoptera, Megachilidae, Megachilini), ZooKeys 221, pp. 31-61 : 37-40

Megachile (Litomegachile) brevis Say, 1837

Megachile brevis Say, 1837: 407. Syntypes male and female, USA: Indiana (destroyed).

Megachile lanuginosa Smith, 1853: 190. Syntypes male, female, USA: Florida (BMNH).

Megachile nupta Cresson, 1872: 268.Lectotype female, USA: Texas (USNM). Megachile perbrevis Cresson, 1878: 127. Lectotype male, USA: Texas (USNM).

Diagnosis.

Megachile brevis most closely resembles Megachile onobrychidis , Megachile pseudobrevis , and Megachile coquilletti . The female can be separated from these species by the combination of the ivory colored scopa, with a few black setae apically on S6, and with a small amount of white appressed pubescence apically on T6 (Figure 5A). The comparable species have more black setae and no white appressed pubescence on T6. The male has brown tarsi that distinguish it from Megachile coquilletti (Figure 4E), and a tomentum on T6 which distinguishes it from Megachile onobrychidis .

Female. Body length9-12 mm. Mandible 4-toothed, with no angulation between teeth 3 and 4 (Figure 4A). Head with white pubescence, vertex with black pubescence. Mesosoma with white pubescence, scutum with black pubescence. T2-3 with deep transverse basal grooves, T4 with shallow groove. T1 with white pubescence, T2 with white pubescence basally and black pubescence apically, T3-5 with black pubescence. T6 convex basally and concave apically in profile, and concave laterally in dorsal view; with black erect setae basally and black appressed pubescence, with some white appressed pubescence apically. S1-5 with ivory setae; S6 with ivory setae and few black setae apically (Figure 5A).

Male. Body length7-9 mm. Mandible 3-toothed.Ocellocular distance equal to ocelloccipital distance (Figure 4D). Head with white pubescence. All mesosomal pubescence white or ivory (may appear yellow in early season specimens). T1-5 with white discal pubescence. T5 with complete apical fringe of white hair that covers marginal zone. T6 with tomentum (Figure 6G); transverse carina variable in shape, but usually with indistinct medial notch and asymmetrical jagged projections; true apical margin with submedial teeth closer to lateral teeth than each other (Figure 6B). Genitalia and hidden sterna shown in Figures 7A1-A4.

Variability.

The transverse carina of the male can vary significantly in this species, with some specimens barely showing any medial emargination, but most with jagged projections, where others have a medial notch.Females can have a few black scopal setae on S6 or all ivory colored scopae.

Distribution of material examined.

USA: California: Calaveras, Lake, Orange, Placer, Riverside, Sacramento, San Diego, San Joaquin, Siskiyou Tulare and Yolo Counties (May-Oct.); Colorado: Weld County (Sep.); Idaho: Bingham County (Jun.); Nebraska: Dawes County (Aug.); New Mexico: Eddy County (Oct.); Nevada: Churchill County (Jun); New York: Suffolk County (Aug.); Oklahoma: Marshall and Oklahoma Counties (Apr.); Oregon: Jackson County (Sep.); Texas: Gregg and Tyler Counties (Jun.-Sep.); Utah: Garfield and Washington Counties (Apr.-Sep.); 67 females, 68 males.

Ecology.

Michener (1953) published a detailed biology of Megachile brevis including a description of nest making, provisioning and development. Megachile brevis flies during the warmest parts of the year, with two to four generations per year, depending on locality and resources. It disperses widely from its natal site. Michener found that flower sources used by this species are diverse, but female bees tend to have a preference for blue, purple and white flowers, and a general faithfulness to a single type of pollen per collecting trip. Megachile brevis nested in a variety of situations, always nesting in preexisting hollows, including stems, burrows of other insects, dense foliage or spaces between rocks ( Michener 1953). He also observed that Megachile brevis hunted for nesting sites by flying a few inches above the ground, and tended to nest near the soil surface. Larvae go through at least 4 instars ( Baker et al. 1985). Megachile brevis nests are parasitized by a variety of species, including the megachilids Coelioxys sayi Robertson and Coelioxys octodentata Say, a clerid beetle ( Phyllobeanus sp.), and wasps, including Aprostocetus coelioxydis Burks ( Eulophidae ), Leucospis affinis affinis Say ( Leucospidae ) and Melittobia chalybii Ashmead ( Eulophidae ) (Baker, 1985).

Flower records.

Ailanthus sp. ( Simaroubaceae ), Amorpha canescens ( Fabaceae ), Baptisia sp. ( Fabaceae ), Cassia chamaecrista ( Fabaceae ), Centaurea jacea ( Asteraceae ), Erigeron philadelphicus ( Asteraceae ), Fagopyrum esculentum ( Polygonaceae ), Fallugia paradoxa ( Rosaceae ), Gossypium sp. ( Malvaceae ), Grindelia squarrosa ( Asteraceae ), Helianthus maximiliani ( Asteraceae ), Helianthus tuberosus ( Asteraceae ), Heliopsis scabra ( Asteraceae ), Kuhnistera purpurea ( Fabaceae ), Kuhnistera oligophylla ( Fabaceae ), Lactuca pulchella ( Asteraceae ), Machaeranthera tanacetifolia ( Asteraceae ), Marrubium vul gare ( Lamiaceae ), Medicago sativa ( Fabaceae ), Melilotus alba ( Fabaceae ), Melilotus officinalis ( Fabaceae ), Mentzelia sp. ( Loasaceae ), Meriolix serrulata ( Onagraceae ), Oxalis violacea ( Oxalidaceae ), Phyla incisa ( Verbenaceae ), Polygonum aubertii ( Polygonaceae ), Polygonum hydropiperoides ( Polygonaceae ), Psoralea floribunda ( Fabaceae ), Schrankia uncinata ( Fabaceae ), Solidago canadensis ( Asteraceae ), Solidago nemoralis ( Asteraceae ), Solidago rugosa ( Asteraceae ), Symphoricarpos occidentalis ( Caprifoliaceae ), Trifolium hybridum ( Fabaceae ), Vernonia baldwinii ( Asteraceae ).

Comments.

Megachile brevis is the type species of the subgenus Litomegachile . It ranges across North America, north to southern Saskatchewan, Canada, and south into Mexico. There is also a record from as far south as northern Costa Rica (not shown on map) ( Ascher and Pickering 2011) (Figure 8).