Osmia (Diceratosmia) azteca Cresson

Rightmyer, Molly G., 2017, A revision of the subgenus Osmia (Diceratosmia), with descriptions of four new species (Hymenoptera, Megachilidae), Zootaxa 4337 (1), pp. 1-37 : 5-6

Osmia (Diceratosmia) azteca Cresson

( Figs 1B , 9A )

Osmia azteca Cresson 1878: 105 [Holotype female: Philadelphia].

Osmia erythrotricha Cockerell 1912: 561 –562 [Holotype female: San Francisco]; Michener 1949: 260 [synonymy with O. azteca azteca ].

Osmia mea Strand 1921: 303 [Holotype male: Eberswelde; not confirmed by present authors]; Tkalců 1986: 231 –232 [synonymy].

Osmia costaricensis Friese 1925: 37 –38 [Syntype males and females: Berlin]; Michener 1949: 260 [synonymy with O. azteca costaricensis ].

Diceratosmia azteca (Cresson) ; Sandhouse 1939: 139.

Diceratosmia azteca azteca (Cresson) ; Michener 1949: 260.

Diceratosmia azteca costaricensis (Friese) ; Michener 1949: 260.

Osmia (Diceratosmia) azteca Cresson ; Sinha 1958: 230.

Diagnosis. Females of O. azteca can be distinguished from all other Diceratosmia by the combination of their large size (i.e., intertegular distance 3.0– 3.3 mm), dark brown to black (non-metallic) integument (metallic blue or green in other species), and reddish or golden orange scopal hairs ( Fig. 9A ). Osmia azteca are most similar to O. exquisita based on their relatively large size and reddish or orange-golden scopal hairs (body size smaller and scopa white to pale golden in other species). In addition to the difference in integument color, female O. azteca differ from O. exquisita by the much smaller projection on the apical tip of S6 (shorter than surrounding hairs in O. azteca , longer than surrounding hairs in O. exquisita ). In O. azteca , the third tooth of the mandible is well differentiated from the fourth due to a relatively strong carina at the base of the third tooth and V-shaped emargination between the third and fourth teeth (third tooth only weakly differentiated from fourth in O. exquisita due to a weak basal carina and very shallow U-shaped emargination between the two teeth). On the apical half of the mandible above the outer ridge in O. azteca hairs are sparse, suberect, slender and does not obscure the integument beneath, while in O. exquisita , hairs are decumbant, stout, spatulate and very dense such that they obscure the integument beneath.

Males of O. azteca are readily distinguished from all other Diceratosmia due to their relatively large size (intertegular distance ca. 2.5 mm), dark brown to black integument, and reddish to pale golden hairs. The male of O. exquisita is unknown but is likely to be of a similar size and potentially could have reddish golden hairs covering much of the body as in O. azteca , but is expected to have metallic blue-green integument as in the females that will distinguish it from O. azteca .

Distribution. Mesoamerica. Recorded from central and southern Mexico, Guatemala and Costa Rica ( Fig. 14 ).

Material Examined. Costa Rica. San José: Escazu , 30 Jul 1985, FD Parker; Escazu, 27 Dec 1988, FD Parker ; San Jose, 22 Apr 1989, FD Parker ; 27 Dec 1987, FD Parker; Santa Ana, 3 mi S, 27 Dec 1988, FD Parker. Guatemala. Sacatepéquez: Antigua, 28 Sep 1982, H Suzuki . Mexico . Chiapas: Cerro Mozotal, SW slope, 22 Nov 1976, DE Breedlove, JA Breedlove; Paraje Vobits, 28 Oct 1976, DE Breedlove, JA Breedlove. Distrito Federal: El Pedregal de San Angel , 12 Nov 1991, T Griswold; El Pedregal de San Angel , 13 Nov 1991, T Griswold; Mexico City, 4 Nov 1987, C Dominguez; San Angel, Jul 1903, WL Tower & Schrammel . Durango : Durango, 16 mi W, 22 Oct 1957, HA Scullen . Hidalgo: Metzquititlan , 22 km SW, 11 Nov 1991, T Griswold; Metzquititlan, 4 km N, 11 Nov 1991, T Griswold; Pachuca, 10 mi E, 10 Jul 1963, HA Weems Jr; Sahagun, 7 Sep 1986, Rodriguez; Sahagun, 14 Sep 1986, Rodriguez; Zimapan, 8 Oct 1957, HA Scullen . Jalisco: El Aguacate, 14.7 mi SW Yahualica , 14 Sep 1986, DK Faulkner; La Soledad, 8 km SW La Manzanilla , 4 Nov 1990, CM Estrada; Tepatitlan , 3 Oct 1966 GE & AS Bohart; Tepatitlan, 17 Sep 1970, GE & RM Bohart . Mexico: Altocomulco , 18 Aug 1954 . Michoacán: Taucitaro , 11 Oct 1982, R Ayala; Tzintzuntzán, N Patzcuaro, 26 Oct 1987, T Griswold . Morelos: Cuernavaca , 8 Nov 1987, FD Parker; Cuernavaca, 13 Nov 1987, FD Parker; Tepotzlan, 15 Oct 1980, R Murillo; Tepozltlan, 4.5 km NW, 14 Oct 1995, O Yáñez; Tepozltlan, 4.5 km NW, 27 Oct 1996, O Yáñez . Puebla: El Seco , 29 km SW, 6 Nov 1991 T Griswold; UDLA [Cholula], 30 Aug 1998 . Sonora: Yecora , 17 Aug 1991, JG Rozen, N Pember . Tlaxcala: Huamantla, Parq. Nac. La Malinche , Cam. La Malinche-Carr. Apizac , 11 Sep 1998, T Griswold . Zacatecas: Salinas , 19 mi E, 10 Sep 1973, WJ Hanson, BA Haws; Tepechitlan, 35 km SW, 14 Sep 1984, WJ Pulawski.

Floral Associations. Asteraceae : Simsia lagascaeformis, Tagates , Tithonia , T. tubaeformis ; Nyctaginaceae : Abronia minor .

Comments. Osmia azteca is unique among Diceratosmia in the complete lack of metallic color. Cockerell (1912: 561–562), when discussing the synonym O. erythotricha , commented upon the species’ similarity to the unrelated O. pseudoaurulenta Dours [= Osmia (Helicosmia) tunensis (Fabricius) ], and speculated that the former might also use snail shells as a nesting substrate; however, the nesting biology for this species remains unknown. The holotype of Osmia mea was studied by one of us (TG) in 1984 during a study of osmiine types in European Museums. Notes at the time suggested its placement in the subgenus Helicosmia Thomson, under the mistaken assumption that it was a Palaearctic species. In retrospect the stout head, body size and coloration that would indicate Helicosmia could equally apply to O. azteca .

Figures

FIGURE 1. Female mandibles: A) O. marilaunidii (DRO 0115730), B) O. azteca (34211), C) O. conjunctoides (BBSL 204519), D) O. exquisita (BBSL 989169). Scale bar = 0.25 mm.

FIGURE 9. Female habitus lateral view: A) O. azteca (BBSL 839523), B) O. exquisita (BBSL 989169). Scale bar = 0.5 mm.

FIGURE 14. Known distribution of O. azteca (orange triangles) with expected distribution based on maxent modeling (rose coloring). Scale bar = 200 km.