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Revista de la Sociedad Entomológica Argentina

versión impresa ISSN 0373-5680versión On-line ISSN 1851-7471

Rev. Soc. Entomol. Argent. v.66 n.3-4 Mendoza ago./dic. 2007

 

A review of the albidohirta group of Ptilothrix (Hymenoptera: Apidae: Emphorini)

Revisión del grupo albidohirta de Ptilothrix (Hymenoptera: Apidae: Emphorini)

Roig Alsina, Arturo

Museo Argentino de Ciencias Naturales «Bernardino Rivadavia,» Av. Angel Gallardo 470, 1405 Buenos Aires, Argentina; e-mail: arturo@macn.gov.ar

RESUMEN. El grupo albidohirta de Ptilothrix Smith incluye tres especies: Ptilothrix albidohirta Brèthes, P. concolor sp. nov. y P. nemoralis sp. nov. Este grupo se conoce del oeste y norte de la Argentina y del centro de Bolivia. Una de sus especies, P. albidohirta, llega hasta los 3.600 m s.n.m. en la cordillera de los Andes, en tanto que las otras dos especies habitan en el llano. Se caracteriza el grupo y se describen e ilustran las especies.

PALABRAS CLAVE. Abejas; Emphorini; Argentina; Bolivia.

ABSTRACT. The albidohirta group of Ptilothrix Smith includes three species: Ptilothrix albidohirta Brèthes, P. concolor sp. nov., and P. nemoralis sp. nov. The group is known from northern and western Argentina and from central Bolivia. One of its species, P. albidohirta, reaches high altitudes in the Andes mountains, up to 3600 m a.s.l., while the other two species occur in the lowlands. A characterization of the group, descriptions of the species, and illustrations are provided.

KEY WORDS. Bees; Emphorini; Argentina; Bolivia.

INTRODUCTION

The genus Ptilothrix Smith is a member of the Emphorini, a tribe of bees restricted to the Western Hemisphere (Michener, 2000). The tribe comprises ten genera (Roig-Alsina, 1999), six of which are restricted to South America, two are broadly distributed throughout the continent, and two (Diadasia Patton and Ptilothrix Smith) have numerous species in North and South America, but are scarce or not represented in Central America. The species of Ptilothrix occur from northcentral eastern U.S.A. to the state of Morelos in Mexico (Michener et al., 1994), and from northern Brazil to northern Patagonia in Argentina. The largest diversity of the genus occurs in temperate South America, but the number of species is difficult to assess, since Ptilothrix has not been reviewed to date.
Species of Ptilothrix are solitary, burrowing bees. Many species are oligolectic, and have been associated with plants mainly of the families Malvaceae, Onagraceae, Convolvulaceae, and Cactaceae (Linsley et al., 1956; Rust, 1980; Hazeldine, 1997).
According to Roig-Alsina (1994) and Sipes & Tepedino (2005), Ptilothrix shares derived features with Diadasina Moure and Alepidosceles Moure, suggesting that these three genera are closely related. Ptilothrix is distinguished, among other emphorines, by a suite of characters that includes the lack of arolia, the elongate first flagellomere, the bowed, elevated upper margin of the clypeus coupled with a short proboscis, the reduced apical projection of the female hind basitarsus, and the type of scopal hairs on the outer surface of the hind tibia, which have the branches not retrorse, but arising at acute angles to the axes of the hairs and directed apicad.
The present contribution deals with a small group of species restricted to northern Argentina and Bolivia. Although the three species included in the group are morphologically homogeneous, they are strikingly different in their color pattern and vestiture.

MATERIAL AND METHODS

Terminology for structures follows Michener (1944, 2000), except that metapostnotum is used instead of propodeal triangle (Brothers, 1976). The maximum diameter of the median ocellus (MOD) is used as a reference to express the length of the pubescence and other structures. In the descriptions, the metasomal terga (T) and sterna (S) are identified with Arabic numerals.
Specimens studied are deposited in the following institutions: Museo Argentino de Ciencias Naturales «Bernardino Rivadavia,» Buenos Aires (MACN); Museo de La Plata, La Plata (MLP); Instituto y Fundación Miguel Lillo, Tucumán (IFML); American Museum of Natural History, New York (AMNH); Zoologische Staatssammlung, München (ZSM). Acronyms are used to indicate depositories of the specimens.

RESULTS

albidohirta group

This species-group includes Ptilothrix albidohirta Brèthes and the two new species P. concolor and P. nemoralis. The group is known from northern and western Argentina and from central Bolivia (Fig. 10). One of the species, P. albidohirta, occurs in the Puna region, reaching high altitudes; records for this species range from 2200 m to 3600 m a.s.l. The other two species occur in the lowlands, P. concolor in the Monte region and P. nemoralis in the Chaco region.
The group is characterized by the slender, short-branched scopal hairs on the outer surface of the hind tibia of the female, by the lack of an apical white brush of hairs on the hind tibia, and by the digitiform projection of the inner lobe of the seventh sternum of the male (although males of P. nemoralis are as yet unknown).
The three species differ considerably in their appearance. Ptilothrix albidohirta resembles Diadasia baeri (Vachal), another hirsute, pale-colored emphorine, with which it is sympatric in the Andes mountains. Ptilothrix concolor resembles a large, ordinary Diadasia, due to its short, appressed, yellowish-brown vestiture. On the contrary, Ptilothrix nemoralis bears a color pattern that is typical for a large number of species of Ptilothrix, with a rufous dorsum of the thorax and a yellow banded metasoma.

Ptilothrix albidohirta Brèthes, 1910 (Figs. 4-7, 10)


Figs. 1-9. Figs. 1-3, Ptilothrix concolor n. sp., male. 1, S7, ventral (left) and dorsal (right) views. 2, S8, ventral view. 3, apex of T7. Figs. 4-6. Ptilothrix albidohirta Brèthes, male. 4, S7, ventral (left) and dorsal (right) views. 5, S8, ventral view. 6, apex of T7. Figs. 7-9, hairs of center of outer surface of hind tibia of female. 7, P. albidohirta Brèthes. 8, P. concolor n. sp. 9, P. nemoralis n. sp. Scale bars = 0.1 mm.


Fig. 10. Distribution map of the species of the albidohirta group: P. albidohirta Brèthes (dots), P. concolor n. sp. (stars; open star indicates imprecise locality in La Rioja province), and P. nemoralis n. sp. (diamonds).

Ptilothrix albidohirta Brèthes, 1910: 295-296 (Holotype male, 7892, Jujuy, Argentina, MACN, examined); Schrottky, 1913: 254; Hazeldine, 1997: 33-35, figs. 16-17 (biology); Roig-Alsina, 1999: 25.

Diagnosis. This species is distinguished by its hirsute vestiture all over the body. The metasoma of both sexes is clothed with long, erect hairs, lacking the appressed bands characteristic of many other Ptilothrix. It is also characterized by the color of the vestiture, greyish on the head and mesosoma, and yellowish to orange on the metasoma; the vestiture of the legs is pale in males, but mostly black in females.

Redescription. Female. Length: 10.3- 12.8 mm; length of forewing: 8.8-10.3 mm. Color: Black, except middle of mandible, apex of tarsi, and translucent outer margin of tegula reddish brown. Membrane of wings: slightly infuscate; pterostigma and veins: dark brown to black.
Pubescence. Hairs: gray to pale yellowish-brown on head, mesosoma and T1; hairs grayish, partly dusky, on underside of coxae, trochanters and front and mid femora, rest of legs with hairs black, including scopal hairs. Hairs: yellowish brown (with orange hue in fresh specimens) on T2-T6 and on metasomal sterna; prepygidial fimbria orange. Pubescence of head and thorax: long and erect, hairs on center of scutum 2.5-3.0 times MOD, hairs on mesopleuron also 2.5-3.0 times MOD, hairs on postero-lateral angles of propodeum 3.0-4.0 times MOD. Metapostnotum: clothed with sparse hairs, 0.8-1.2 times MOD. Tibial scopa with hairs on outer surface 1.8-2.0 times MOD, with rachis slender and 16-20 branches directed apicad (Fig. 7). Metasomal terga: densely covered with erect hairs, 1.5-2.2 times MOD, completely lacking appressed hairs.
Sculpture. Clypeus and labrum with dense punctures; punctures on disc of clypeus 0.3-0.5 diameters apart, with interspaces shiny, elevated, giving rugose appearance. Punctation around and above antennal sockets similar to that of clypeus, but with tessellate interspaces; rest of head more finely punctured; vertex around ocelli finely tessellate, except small shiny area close to lateral ocellus. Punctures on scutum, scutellum, and mesopleuron dense, on center of scutum 0.2-1.0 diameters apart, with weakly tessellate interspaces. Metapostnotum tessellate. Metasomal terga tessellate between punctures.
Structure. Inner orbits nearly straight and parallel. Ocellocular and interocellar distances subequal. Clypeus 1.9-2.0 times wider than long, protuberant in lateral view for a distance 0.65 times maximum eye width. Labrum trapeziform, with pointed apex, 1.5 times as broad as median length. Interantennal distance 2.5-2.8 times antennocular distance. First flagellomere 2.2 times longer than its apical width; proportion of lengths of scape, pedicel and proximal three flagellomeres 1.7:0.5:1:0.3:0.35.

Male. Length: 8.0-13.0 mm (holotype 10.3 mm); length of forewing: 8.5-10.5 mm (holotype, 8.7 mm). Color, pubescence and sculpture: similar to those of female, except as follows. Hairs: gray to pale yellowishbrown all over the body, including legs and metasoma. Hairs on head and thorax longer, those on scutum 3.5-4.3 times MOD, on mesopleuron 3.3-4.3 times MOD. Hairs on metasomal terga: erect, long, on T2 2.2-2.8 times MOD. S2-S4 with long, erect hairs, and apical fringes poorly defined; S5 with hairs short medially and longer laterally. S6 bare basally and laterally, apically with dense median tuft of erect hairs.
Structure. Labrum rectangular, with polished, rounded median apical projection. First flagellomere 2.1 times as long as its apical width; proportion of lengths of scape, pedicel and proximal three flagellomeres 1.9:0.4:1:0.5:0.55. T7 ending in two sharp apical points separated by notch with straight base (Fig. 6). S7 and S8 as in Figs. 4-5. Gonostylus filiform.

Material examined. ARGENTINA. Jujuy: 2 males, Abrapampa, 3400 m, 5-III 1960, R. Golbach (IFML); 1 male, Iturbe, 3300 m, 8-III-1960, R. Golbach (IFML); 1 female, 1 male, Humahuaca, 24-I-1973, L. Stange (IFML); 2 females, 1 male, Tilcara, 2400 m, 20-III-1967, L. Stange & A. Willink (IFML); 1 female, 3 males, Tilcara, 9-III-1965, A. Willink (IFML); 1 male, Tilcara, II-1989, Fritz (AMNH); 1 female, 1 male, Uquía, 2800 m, Quebrada de Humahuaca, 17-III-1978, A. Willink & P. Fidalgo (IFML); 8 females, 8 males, Maimará, 19-III-1990, A. Roig A. (MACN); 2 females, 9 males, Maimará, 7-III- 1965, A. Willink (IFML); 8 females, Purmamarca, 15-III-1978, A. Willink & P. Fidalgo (IFML); 1 female, 5 males,Volcán, 2100 m, 12-III-1960, R. Golbach (IFML). Salta: 4 males, Amblayo, 2500 m, 30-I-1945, F. Monrós (MLP); 23 females, 5 males, Chorrillos, 15-III-1993, P. Hazeldine (MACN); 8 females, 9 males, Tastil, 3000 to 3600 m, III-1985, III-1986, III-1994, I-1995, III-1996, M. Fritz (MACN); 9 females, 4 males, Tastil, III-1985, III-1988, II-1992, M. Fritz (AMNH); 2 females, El Alisal, III-1988 and IV-1988, M. Fritz (AMNH); 14 females, 7 males, El Alisal, II-1983, III-1985, IV-1988, II-1989, III-1993, III-1994, M. Fritz (MACN); 1 female, El Maray, 2200 m, M. Fritz (MACN). La Rioja: 2 males, Cuesta de la Aguadita, 9 km S Angulos, 25-II-1978, A. Willink & E. Domínguez (IFML). BOLIVIA. La Paz: 1 female, Irpavi, 3200 m, 4-IV-1938, F. Tippmann (ZSM). Cochabamba: 2 males, Morochata, 2900 m, R. Zischka (MLP); 1 female, Cochabamba, R. Zischka (MLP); 1 male, Cochabamba, 2500 m, W. Wittmer (MLP).

Ptilothrix concolor sp. nov. (Figs. 1-3, 8, 10)

Diagnosis. This species is readily separated from all other Ptilothrix by its homogeneous pale-colored vestiture, short and appressed on the metasoma, similar to that of many species of Diadasia.

Description. Holotype female. Length: 13.5 mm (paratypes, 11.0-12.0 mm); length of forewing 10.0 mm (paratypes, 9.5-10.3 mm). Color. Black, except base of mandible, underside of flagellum and all legs beyond coxae brownish, tibial spurs and tarsi reddish brown; tegula translucent, yellowish. Wings: hyaline, except slightly infuscate on marginal cell; veins and pterostigma dark brown.
Pubescence. Uniformly pale, gray to whitish on face, underside of thorax and pleurae, pale yellowish-brown on dorsum of thorax, metasoma and most of legs; T2-T4 with weakly defined narrow yellow apical bands, due to denser pubescence. Outer surface of hind tibia without distinct tuft of white hairs. Prepygidial and pygidial fimbriae reddish brown. Pubescence of head and thorax dense, short on scutum, hairs on center of scutum 0.7-1.2 times MOD, hairs on mesopleuron longer, 1..5-2.5 times MOD, hairs on postero-lateral angles of propodeum 3 times MOD. Metapostnotum clothed with sparser hairs, 0.8-1.5 times MOD. Tibial scopa with hairs on outer surface 1.4-1.8 times MOD, with rachis slender and 14-18 branches directed apicad (Fig. 8). Metasomal terga densely covered with appressed, short hairs, 0.4-0.7 times MOD, intermixed with sparse, erect, long hairs; appressed hairs denser on posterior margin of terga, forming weakly defined apical bands.
Sculpture. Clypeus and labrum with dense, regularly distributed punctures; those on disc of clypeus 0.3-0.5 diameters apart; intespaces shiny. Punctation around and above antennal sockets similar to that of clypeus; rest of head more finely punctured; vertex around ocelli smooth. Punctures on scutum, scutellum, and mesopleuron similar to those of clypeus, 0.5-1.0 diameters apart, and also with shiny interspaces. Metapostnotum with shiny interspaces between punctures. Metasomal terga finely punctured.
Structure. Inner orbits nearly straight, converging below, upper to lower interocular distance 1.1:1. Ocellocular distance smaller than interocellar distance (0.9:1). Clypeus 1.7 times wider than long, protuberant in lateral view for a distance 0.65 times maximum eye width. Labrum trapeziform, with pointed apex, 1.5 times as broad as median length; apex truncate with antero-apical margin carinate. Interantennal distance 3 times antennocular distance. First flagellomere 1.65 times longer than its apical width; proportion of lengths of scape, pedicel and proximal three flagellomeres 2.4:0.5:1:0.4:0.4.

Male. Length: 12.0 mm; length of forewing 10.0 mm. Color, pubescence and sculpture similar to those of female, except as follows. Hairs on head and thorax longer, those on scutum 1.0-1.4 times MOD, on mesopleuron 2.3-3.0 times MOD. Hairs on metasomal terga semierect, not appressed, short, on T2 0.6-0.7 times MOD. Hairs of apical fringes of S2-S4 as long medially as laterally, but those on S5 very short medially. S6 bare basally and laterally, apically with dense median tuft of erect hairs.
Structure. Labrum rectangular, with weakly trilobate apical projection. First flagellomere nearly twice (1.8 times) as long as its apical width; proportion of lengths of scape, pedicel and proximal three flagellomeres 2.4:0.6:1:0.55:0.6. T7 ending in two short apical points broadly separated by U-shaped notch (Fig. 3). S7 and S8 as in Figs. 1-2. Gonostylus filiform.

Etymology. The name refers to the homogeneous pale vestiture of the species.

Type material. ARGENTINA. Catamarca: Holotype female, San Fernando, 4-6-XI-1989, L. Moffatt (MACN); 1 paratype male,same data as holotype (MACN); 1 paratype female, Tinogasta, 8-III-1990, J.G. Rozen & A. Roig A. (AMNH). La Rioja: 1 paratype female, X- 1925, M. Gómez (MACN); 1 paratype female, 18-II-1922, M. Gómez (MACN).

Ptilothrix nemoralis sp. nov. (Figs. 9, 10)

Diagnosis. This species is distinguished among all other Ptilothrix with yellowbanded metasoma by the pattern of the bands, covering almost all exposed surface on T2-T3 and interrupted on T4, and by the lack of the white tuft of hairs on the apex of the hind tibia.

Description. Holotype female. Length: 9.2 mm (paratype, 8.8 mm); length of forewing: 7.5 mm (paratype, 7.3 mm). Color. Black, except middle of mandible, underside of flagellum, and all legs brownish; tibial spurs and translucent tegula yellowish brown. Membrane of wings amber; pterostigma and veins yellowish.
Pubescence. Hairs whitish on clypeus, labrum, around antennal sockets, and on lower half of gena; rufous in front and behind ocelli on vertex. Hairs rufous on dorsum of thorax, propodeum, and upper half of pleurae, becoming paler towards venter of thorax; whitish on underside of coxae, trochanters and femora; rest of legs with brown hairs; outer surface of hind tibia without distinct tuft of white hairs. Metasomal T1 on basal vertical surface with erect yellowish hairs; apex of tergum with band of pale yellow to yellowish brown, appressed, short hairs. T2-T3 with broad pale yellow apical bands occupying most of exposed surface of terga; basad to the bands with short black hairs. T4 with narrower pale yellow band broadly interrupted in middle; base and center of T4 with black hairs and pale yellow band with sparse, erect, black hairs. Hairs on T5-T6 black, on metasomal sterna brown. Hairs on center of scutum 0.9-1.0 times MOD, hairs on mesopleuron longer, 1.5-1.8 times MOD, hairs on postero-lateral angles of propodeum 2.0-2.3 times MOD.
Metapostnotum clothed with sparser hairs, 1.0-1.5 times MOD. Tibial scopa with hairs on outer surface 1.0-1.4 times MOD, with rachis slender and 18-22 branches directed apicad (Fig. 9). Metasomal terga densely covered with appressed, short hairs, those on apical band of T2 0.3-0.35 times MOD. Sculpture. Labrum with dense, regularly distributed punctures. Clypeus on lower third with punctures 0.3-0.5 diameters apart, but on upper third 1-2 diameters apart; interspaces shiny. Punctation around and above antennal sockets similar to that of lower third of clypeus; rest of head more finely punctured; vertex around ocelli smooth. Punctures on scutum dense, 0.3-1.0 diameters apart, with shiny interspaces; on mesopleuron similar to those of scutum, but interspaces tessellate. Metapostnotum tessellate close to metanotum, remainder of metapostnotum shiny. Metasomal terga finely punctured.
Structure. Inner orbits nearly straight, converging below, upper to lower interocular distance 1.1:1. Ocellocular distance smaller than interocellar distance (0.75:1). Clypeus 1.8 times wider than long, protuberant in lateral view for a distance 0.5 times maximum eye width. Labrum trapeziform, 1.68 times as broad as length; apex truncate with anteroapical margin carinate. Interantennal distance 3.4 times antennocular distance. First flagellomere 1.8 times longer than its apical width; proportion of lengths of scape, pedicel and proximal three flagellomeres 2.56:0.56:1:0.4:0.4.

Etymology. The specific name, which means «from the forest» in Latin, alludes to the habitat of the species, as opposed to the habitat of the other two species of the group, which occur in areas with more open and shrubby vegetation.

Type material. ARGENTINA. Formosa: Holotype female, Pozo de Maza, Departamento Bermejo, II-1989, P. Arenas (MACN); 1 paratype female, Gran Guardia, II-1957, J. Foerster (MLP).

ACKNOWLEDGEMENTS

I am indebted to the curators of the collections listed in the section Material and methods for the loan of specimens, J. G. Rozen, Jr. (AMNH), M. V. Colomo de Correa (FIML), J. A. Schnack (MLP), and K. Schönitzer and J. Schuberth (ZSM); to C. D. Michener and L. Ruz for helpful comments on the manuscript. This study was funded by the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina, PIP 5755.

LITERATURE CITED

1. BRÈTHES, J. 1910. Himenópteros argentinos. An. Mus. Nac. Buenos Aires 20: 205-316.
2. BROTHERS, D. J. 1976. Modifications of the metapostnotum and the origin of the 'propodeal triangle' in Hymenoptera Aculeata. Syst. Entomol. 1: 177 182.
3. HAZELDINE, P. L. 1997. Comportamiento de nidificación de cuatro especies de Ptilothrix Smith. Physis, Sec. C, Buenos Aires 54: 27-41.
4. LINSLEY, E. G., J. W. MACSWAIN & R. F. SMITH. 1956. Biological observations on Ptilothris sumichrasti (Cresson) and some related groups of emphorine bees. Bull. South. California Acad. Sci. 55: 83-101.
5. MICHENER, C. D. 1944. Comparative external morphology, phylogeny, and a classification of the bees. Bull. Am. Mus. Nat. Hist. 82: 151-326.
6. MICHENER, C. D. 2000. The Bees of the World. The John Hopkins University Press, Baltimore and London. xiv + 1-913 pp.
7. MICHENER, C. D., R. J. McGINLEY & B. N. DANFORTH. 1994. The Bee Genera of North and Central America. Smithsonian Institution Press, Washington D.C. x + 209 pp.
8. RUST, R. W. 1980. The biology of Ptilothrix bombiformis (Hymenoptera: Anthophoridae). J. Kansas Entomol. Soc. 53: 427-436.
9. ROIG-ALSINA, A. 1994. Meliphilopsis, a new genus of emphorine bees, and notes on the relationships among the genera of Emphorina (Insecta: Hymenoptera: Apoidea: Apidae). Reichenbachia 30: 181-188.
10. ROIG-ALSINA, A. 1999. Sinopsis genérica de la tribu Emphorini, con la descripción de tres nuevos géneros (Hymenoptera, Apidae). Physis, Sec. C, Buenos Aires 56: 17-25.
11. SCHROTTKY, C. 1913. La distribución geográfica de los himenópteros argentinos. An. Soc. Cientif. Argentina 75: 225 286.
12. SIPES, S. D. & V. J. TEPEDINO. 2005. Pollen-host specificity and evolutionary patterns of host switching in a clade of specialist bees. Biol. J. Linn. Soc. 86: 487-505.
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Recibido: 19-04-2007;
aceptado: 28-08-2007

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