Joergensenella, a new subgenus of Neotropical Megachile (Hymenoptera: Megachilidae), with a key to Argentinean Megachile with specialized facial pollen-harvesting hairs

A new subgenus of Megachile, Joergensenella n. subg., is described for the Neotropical Region. It is distributed in Argentina, southern Brazil, and Uruguay. Males run to Chrysosarus in available keys to subgenera of Megachile, and have been included as such in recent catalogs, while the females run in the keys, and have been included in catalogs, as Dasymegachile or Cressoniella. Association of sexes for all the species are presented for the first time. Besides the type species, M. joergenseni Friese, the following are included in the subgenus Joergensenella: M. bruneriella Cockerell, M. una Vachal, M. lujanense n. sp. (from Mendoza, Argentina), M. fidalgoi n. sp. (from Jujuy, Argentina), M. puntana n. sp. (from San Luis and Tucumán, Argentina), and M. yana n. sp. (from La Rioja, Argentina). Females of one of the species included, M. (Joergensenella) una, bear specialized hairs on the face for the collection of pollen from nototribic flowers. A key is presented to separate this species from other two Megachile in Argentina with a similar specialization: M. (Dasymegachile) schwimmeri Engel, and M. (Cressoniella) boliviensis Friese.


INTRODUCTION
The genus Megachile Latreille is the largest genus of bees in the Neotropical Region, with over 400 valid species recognized at present (Raw, 2007, Asher & Pickering, 2018. The scope of this genus of worldwide distribution has varied depending on the inclusion or not of those groups that construct their nests with mud or resin together with the leafcutter bees (Michener, 2007). The recognition of a single genus for this enormous complex, as proposed by Michener (2007), is a taxonomic prob-lem on which bee researchers have not reached agreement to date (Trunz et al., 2016;González et al. 2019). The monophyly of the group of subgenera that includes all leafcutter species, i.e. Megachile in a strict sense, is supported by these recent studies. The large South American fauna of Megachile is composed nearly exclusively of leafcutter species, with the single exception of the subgenus Chelostomoides Robertson, which reaches southwards to Argentina (Roig-Alsina, 2019).
The subgeneric classification of Megachile in the Neotropics was built by Mitchell (1934Mitchell ( , 1943Mitchell ( , 1980, and revised by , who recognized 27 valid subgenera in the region. Later additions of new subgenera were made by Raw (2006) and González et al. (2018). In spite of the large number of subgenera recognized for the Neotropical fauna, the present subgeneric classification remains unsatisfactory, with a number of species which cannot be ascribed to a subgenus in the current subgeneric system. González et al. (2018) have underlined the problems of this classification in their recent revision of the subgenera Zonomegachile Mitchell and Rhysomegachile Mitchell. One important setback in the understanding of the Neotropical fauna is the lack of association of sexes for a vast number of species. This is the case for M. joergenseni Friese and related species, which have not been recognized as a distinct lineage. The males of this group run to Chrysosarus Mitchell in available keys to subgenera of Megachile, while the females run in the keys, and have been included in catalogs, as Dasymegachile Mitchell or Cressoniella Mitchell. The purpose of the present contribution is to present the association of sexes for all the species in the group, and to characterize it as a new subgenus.
Females of one species in the new subgenus bear specialized facial hairs on the clypeus and the supraclypeal area for the collection of pollen from nototribic flowers, a specialization that has been described in detail for species in the European fauna (Müller, 1996a(Müller, , 1996b. A key is presented to separate this species from other two Megachile that have a similar specialization in Argentina.

MATERIAL AND METHODS
Terminology for structures follows Michener (2007). The following abbreviations are used: UID, upper interocular distance, LID, lower interocular distance, PD, puncture diameter. The maximum diameter of the median ocellus (MOD) is used as a reference to express the length of the pubescence and other structures. The metasomal terga (T) and sterna (S) are identified with Arabic numerals. In the lists of material studied F stands for female, and M for male. The specimens studied are deposited in the following institutions: Facultad de Agronomía, Universidad de Buenos Aires (FAUBA), Instituto Argentino de Investigación de Zonas Áridas, Mendoza (IADIZA), Museo Argentino de Ciencias Naturales, Buenos Aires (MACN), Museo de La Plata, La Plata (MLP), Natural History Museum, London (NHMUK), and Snow Entomological Collection, Lawrence, Kansas (SEMC).

Genus Megachile Latreille
Joergensenella new subgenus urn:lsid:zoobank.org:act:AF5B57CA-4174-44C2-8468-C17D3A20A224 Type species: Megachile joergenseni Friese, 1908 Description. Bees 6.5-14.0 mm long; from entirely black to pale haired with distinct metasomal apical bands. In three out of the seven included species the scopa is black. Female. Mandible with four teeth, with incomplete cutting edge in second interspace and complete cutting edge in third interspace; apical tooth not broader than second or third; fourth tooth acute. Mandible flattened, with space between distal margin and cutting edges narrow; with outstandingly developed brushes of setae on distal end of acetabular and outer grooves ( Fig 2C); condylar groove also with distal brush. Clypeus usually regularly convex, except in one species (M. una) weakly convex, bearing specialized, bent hairs; apical margin with median denticle. First flagellomere 1.2-1.4x as long as apical width; longer (1.1-1.4x) than second. Preoccipital margin of head nar-Preoccipital margin of head narrowly rounded behind vertex, rounded behind gena. Lateral ocellus nearer to posterior margin of vertex than to eye. Claws with basal seta short and spiniform. Metasoma ovoid, T2 broader than either T1 or T3. T6 with conspicuous erect hairs, slightly concave in profile, and with rounded apex in dorsal view. Metasomal sterna without apical hair fasciae beneath scopa. S6 without bare apical lip, uniformly covered with scopal hairs, except one species (M. una) with median preapical area bare to clothed with few sparse hairs. Male. Mandible tridentate, without basal projection, but lower margin forming preapical angle (absent in M. una). First flagellomere 1.1-1.4x as long as apical width; shorter (0.7-0.8x) than second. Hypostomal area pilose and unmodified. Forecoxa with spine 1.0-1.3x MOD; basad to spine with group of stiff bristles more or less hidden by long plumose hairs. Foretarsus slender to moderately enlarged, with distinct outer fringe. Middle tibial spur present, articulated to tibia. Posterior femur without specialized, longitudinal patch of short hairs on inner dosolateral surface. Metasoma with four exposed sterna. Preapical carina of T6 with median emargination; apical margin of T6 with small lateral tooth and triangular to rounded paramedian projection. Antecosta of S5 with median projection directed apically, bearing tiny spicules. S8 without marginal hairs.
Etymology. The new subgenus is named after Peter Jörgensen, a Danish entomologist that greatly contributed to the knowledge of the bee fauna of Argentina at the beginning of the 20th century.

Comments.
The distinctiveness of Joergensenella has not been recognized to date most probably because of the lack of association of the sexes. Females most resemble species of Dasymegachile or Cressoniella, although they do not agree with all the features of these subgenera, while the males can be easily confused as species of Chrysosarus. As a matter of fact, the type species of the new subgenus, M. joergenseni with its synonym M. atramentata (both names based on females only), has been treated either as Dasymegachile or Cressoniella (Raw, 2002, Durante & Abrahamovich, 2006Raw, 2007;Ascher & Pickering, 2018). It is difficult to define Joergensenella by unique apomorphies, as is true for most subgenera of Megachile, but the outstandingly developed apical brushes of the female mandible may constitute one such feature (Figs. 2C,9,arrow). Similar brushes, although less developed, are present in Austromegachile, Tylomegachile and Cressoniella. Another feature of interest in species of Joergensenella is the spiculate median projection of the antecosta of the male S5 (Figs. 6-8). A median projection of the antecosta of S5 is present among Neotropical subgenera only in Cressoniella and Zonomegachile, although the projection is not spiculate. Among Nearctic subgenera a projection is present in the species included by Mitchell in Derotropis, and in a few species of Xeromegachile, although in the latter the projection is spiniform (Mitchell, 1936(Mitchell, , 1937. Given the importance of mandibular structure in the definition of subgenera and in the construction of keys to subgenera of Megachile, it is of interest to clarify the differences between Joergensenella, Dasymegachile, and Cressoniella. The interpretation of the dentition of the female mandible of Dasymegachile has been confusing and misleading. Mitchell (1943), in his key to subgenera of Neotropical Megachile, charac-terized his new subgenus Dasymegachile by an acute upper tooth of the mandible. His figure  10 (1943, p. 661) portraying the mandible of M. saulcyi Guérin (type species of Dasymegachile) with an acute upper tooth is incorrect and it may have been based on a worn specimen. Later he presented (Mitchell, 1980) an accurate drawing of the mandible of M. saulcyi (p. 63, figure  44) with an incised upper tooth. Nevertheless, in his key on page thirteen (Mitchell, 1980) he indicated that Dasymegachile has an acute upper tooth, and mentioned this condition in Dasymegachile as an exception to the subgenera that he grouped under Cressoniella (treated as a genus), all with a blunt or truncate upper tooth. Michener ( , 2007, in his key to subgenera of the Western Hemisphere, as well as in the text on Dasymegachile, also indicates that the upper tooth is acute in this subgenus. This problem has been partly amended in the new key to subgenera presented by González et al. (2018), where Dasymegachile appears twice in the key, either with an acute or with a broad fourth tooth. Nevertheless, all the species of Dasymegachile that I have been able to examine (some 25 species) have a broad upper tooth, either truncate or incised, and none will run to their couplet 27 (González et al., 2018). Joergensenella can be separated from Dasymegachile by the acute upper tooth in all included species. The subgenera Cressoniella and Joergensenella both have the female mandible with a complete cutting edge in the third interspace and an incomplete one in the second interspace, but in Cressoniella the fourth tooth is truncate or incised, and the apical brushes of the mandible are moderate and restricted to the distal end of the acetabular groove, without brushes on the outer or condylar grooves. Males of the two subgenera are quite different, those of Cressoniella with four-toothed mandibles, without forecoxal spines, and the preapical carina of T6 with a pair of acute teeth. In the key to subgenera of Megachile of the Western Hemisphere presented by González et al. (2018), females of Joergensenella would run to couplet 27, together with those subgenera having cutting edges in the second and third interspaces, S6 without a bare apical rim, mandible with apical tooth not broader than second or third tooth, metasomal sterna with ordinary setae, without entire apical fasciae beneath S2-S4, a four-toothed mandible with the upper tooth acute or right-angular, and an ovoid metasoma. Couplets 27-28 can be modified as follows to include Joergensenella: All males of Joergensenella will run to Chrysosarus in Michener (2007) or in González et al. (2018) keys. In the key of González et al. (2018) males of M. una will run to couplet 20 (since the mandible lacks an inferior angle or projection), while the other species will run to couplet 35 (since an inferior angle on the mandible is present). In all cases males of Joergensenella can be separated from males of Chrysosarus (in a broad sense, including Dactylomegachile Mitchell, Austrosarus Raw, and several problematic taxa) by the lack of a specialized, longitudinal patch of short hairs on the inner dorsolateral surface of the hind femur. 4.-Anterior tibial spur with pointed apex, concolorous with remainder of spur (Fig. 4H). Clypeus with median longitudinal impunctate band (Fig. 2C). Outer surface of mandible polished (Fig. 2C) Mendoza, Argentina, 20-11-1906, Museum für Naturkunde, Berlin, examined, present designation). Jensen Haarup, 1908a: 105;: 110. Jörgensen, 19091912a: 126, 132;1912b: 310. Schrottky, 1913: 247, 251. Megachile joergenseni: Toro & Fritz, 1991: 70. Moure et al. 2007: 999. Megachile burmeisteri Friese, 1908 63, 64, 68 (Lectotype male, Mendoza, Argentina, 20-XII-1906, Museum für Naturkunde, Berlin, examined through photographs, present designation). Jensen- Haarup, 1908a: 106;: 110. Vachal, 1909: 7. Jörgensen, 19091912a: 130, 134;1912b: 311. Schrottky, 1913: 247. Schrottky, 1920. New synonym. Megachile atramentata Cockerell, 1917  Megachile (Dasymegachile) joergenseni: Durante and Abrahamovich, 2006: 795, 796, 797. Raw, 2007: 45. Ascher & Pickering, 2018 Diagnosis. The female is recognized by its entirely black vestiture. It can only be confused with M. yana, from which it is readily distinguished by the median impunctate longitudinal stripe of the clypeus (Fig. 2C), and the anterior tibial spur with the apex concolorous with the remainder of the spur (Fig. 4H) Morphology. Inner margin of eyes slightly convergent below, UID 1.13x LID. Distance between lateral ocellus and occipital margin of head 2x MOD. Clypeus 2.24x as wide as long; apical margin with median denticle and crenulate to weakly denticulate on each side of middle. Maximum width of gena 1.0x maximum width of compound eye. Proportions of scape, pedicel and first three flagellomeres 3.3:0.8:1:0.9:0.9; first flagellomere as long as 1.2x its apical width.

Comments.
A female specimen in the Museum für Naturkunde (Berlin) collection is selected as the lectotype of M. joergenseni Friese. It bears the following labels: "Argentina / Mendoza / Diagnosis. This species is distinguished in the female sex by the orange scopa contrasting with the black vestiture of the mesosoma and meta-esosoma and metasomal terga. The male is distinguished, among males with slender forebasitarsus and white vestiture on the metasomal sterna, by the broadly interrupted apical bands on T2-T3 and the black vestiture on the outer surface of the mid and hind femora and tibiae, and on the discs of T3-T4.
Male holotype. Total length 9.3 mm (paratypes 7.8-9.8 mm); length of forewing 7.5 mm (paratypes 6.5-7.8 mm). Color. Integument black, except anterior tarsus with second tarsomere yellowish (with black, ellipsoid spot below), and apex of basitarsus and tarsomeres third to fifth yellowish brown; anterior tibial spur yellowish brown; mid and posterior tibial spurs dark reddish brown; under surface of anterior femur light brown on distal two thirds. Tegula black; wings weakly infuscate, darker along basal vein, costal margin of marginal cell, and apex of forewing; veins and pterostigma dark brown. Pubescence. Head: white on clypeus, paraocular area, antennal scape, lower part of gena, and hypostomal area; black on remainder of head. Mesosoma: black, except white tuft behind pronotal lobe, white hairs on lower part of mesopleuron, and intermixed white and black hairs on anterior and lateral margins of scutum and sides of scutellum. Hairs on disc of scutum long (1.3-1.6x MOD), longer on mesopleuron (1.3-1.8x MOD) and scutellum (1.3-2.3x MOD). Foreleg with long white hairs on apex of coxa, under surface of trochanter, outer side of femur and outer fringe of tarsus; hairs on inner surface of tarsus yellowish brown; remainder of leg with black hairs. Hairs of outer fringe of forebasitarsus 1.4-1.6x apical width of basitarsus, with some interspersed longer hairs up to 2.3x MOD. Mid and hind legs with black hairs, except tarsi with yellowish brown hairs, and outer fringe of mid basitarsus with long white hairs (basal ones up to 3.0x apical width of basitarsus). Metasoma: T1 with hairs black and some interspersed white hairs laterally (entirely black in one paratype); without apical band. T2-T4 with black hairs on disc (1.1-1.4x MOD on T2, 0.8-1.0x MOD on T3); apical bands of plumose white hairs broadly interrupted on T2-T3, briefly so on T4 (apical band complete on T4 in one paratype). T5-T6 on disc with short, plumose, decumbent yellowish hairs (0.3-0.6x MOD on T5) and intermixed long, simple, golden brown hairs (1.1-1.4x MOD on T5); T5 with complete apical band of yellowish plumose hairs. S2-S4 with sparse pale apical hairs (0.8-1.1x MOD medially on S2). Sculpture. Head with punctures on frons nearly coalescent, on vertex separated by shiny interspaces 0.2-0 .5x PD; punctures on disc of scutum separated by weakly tessellate interspaces 0.2-0.8x PD; punctures on mesopleuron below hypoepimeral area coalescent; on discs of T2-T3 separated by shiny interspaces 0.5-1.5x PD. Morphology. Inner margin of eyes slightly convergent below, UID 1.1x LID. Distance between lateral ocellus and occipital margin of head 1.8x MOD. Lower margin of mandible with angle on distal third. Apical margin of clypeus with median emargination, without distinct denticles. Maximum width of gena 0.8x maximum width of compound eye. Proportions of scape, pedicel and first three flagellomeres 3.1:0.8:1:1.3:1.4; first flagellomere 1.12x its apical width. Forecoxal spine present, strong, its length 1.2x MOD; basad to spine with group of stiff, decumbent, reddish setae hidden by long plumose hairs. Anterior basitarsus cylindrical, 3.2x its apical width. Preapical carina of T6 medially emarginate. S5, S6, S8, and genital capsule, as in figures 6Ad-Dd.
Female. Total length 9.6-11.3 mm; length of forewing 7.3-8.8 mm. Color. Integument black, including mandible and antenna; anterior tibial spur yellowish brown with apex darkened distally; mid and posterior tibial spurs dark reddish brown. Wings as in male. Pubescence. Black, except a few white hairs on base of scape, brown hairs on inner side of tarsi, orange hair tufts on apex of mandible, and orange scopa on S3-S4; S2 with orange hairs apically to entirely black; S6 with orange hairs basally to entirely orange. Hairs on disc of scutum long, 1.4-2.1x MOD, longer on mesopleuron (2.1-3.0x MOD). T2-T4 with apical lateral bands of black, plumose hairs; apical hairs on T5 and on T2-T4 medially stiff and simple; discs of T1-T5 with long, erect hairs (1.6-2.1x MOD on T2, 1.0-1.6x MOD on T3); T6 with decumbent, plumose hairs and interspersed erect, simple hairs. Sculpture. Clypeus and supraclypeal area with dense punctures, separated by shiny interspaces 0.10-0.25x PD, and with median longitudinal, irregular, impunctate stripe not reaching apical margin of clypeus. Acetabular interspace of mandible finely tessellate. Punctures on disc of scutum irregularly distributed, separated by weakly tessellate interspaces 0.5-1.2x PD; punctures on mesopleuron below hypoepimeral area separated by tessellate interspaces 0.2-0 .5x PD. Discs of terga shiny; punctures on T3-T5 with posterior margins shallow, poorly defined, appearing as oblong punctures. Morphology. Inner margin of eyes slightly convergent below, UID 1.1x LID. Vertex of head narrow, distance between lateral ocellus and occipital margin of head 1.6x MOD. Clypeus 2.2x as wide as long; apical margin of clypeus with median denticle and weakly denticulate on each side of middle. Maximum width of gena 0.8x maximum width of compound eye. Proportions of scape, pedicel and first three flagellomeres 3.5:0.8:1:0.9:1.0; first flagellomere as long as 1.2x its apical width.
Etymology. The species name is taken from the type locality, department of Luján in the province of Mendoza.
Etymology. The species name is taken from the demonym "puntano" applied to inhabitants of the province of San Luis in Argentina.  Raw, 2002: 31; 85. Ascher & Pickering, 2018. Diagnosis. This species is distinguished by the blunt, apically blackened anterior tibial spur in both sexes, and the pale vestiture. The female bears on the clypeus and supraclypeal area spe- cialized hairs, those on the clypeus with apices sharply bent down and those on the supraclypeal area with wavy apices (Fig. 9). The male is distinguished by its foretarsus with a rufous outer fringe (Fig. 3F-G) and the lack of any marks on the under surface (present in all other species of Joergensenella).

Megachile in Argentina with specialized facial pollen-harvesting hairs
One species in the new subgenus, M. una Vachal, has a pollen-collecting device on the face consisting of specialized hairs on the clypeus and the supraclypeal area (Fig. 9). This structure, related to the collection of pollen from nototribic flowers of the families Lamiaceae and Plantaginaceae, is known to occur in many different taxa of bees (Müller 1996a(Müller , 1996b. At least ten species of bees have this type of pollen-collecting apparatus in Argentina: three species of Anthidium (Megachilidae, González and Griswold, 2013), two species of Anthophora (Apidae, Brooks, 1988), two species of Zikanapis (Colletidae, Compagnucci, 2006), and the three species of The degree of facial modification varies in the three species. Megachile boliviensis has a convex clypeus and supraclypeal area, M. una has a moderately convex clypeus and a weakly convex supraclypeal area, and M. schwimmeri has a weakly convex clypeus and a flat supraclypeal area. The modified hairs on the supraclypeal area reach above to mid level of the antennal sockets in M. boliviensis, but these hairs surpass the upper level of the antennal sockets in the other two species. The hairs on the clypeus are gently curved down in M. boliviensis, but they are sharply curved down at right angles in M. una and M. schwimmeri. In the three species the hairs are distinctly curved down on the clypeus, but on the supraclypeal area they are weakly curved at the apex or have wavy apices. On account of this, it is clear that M. boliviensis has the less modified face, and at the opposite end stands M. schwimmeri. The degree of modification of M. una is closer to that of M. schwimmeri than to that of M. boliviensis.

Key to Megachile females with modified facial hairs in Argentina
1.-Upper tooth of mandible pointed. Apex of mandible with outstandingly developed brush of setae on distal end of acetabular groove, well developed brush on distal end of outer groove, and small brush on distal end of condylar groove (Fig. 9) : Mitchell, 1934: 302. Raw, 2007 Diagnosis. The females are distinguished from other species of Cressoniella by the modified hairs on the clypeus and supraclypeal area. Males are distinguished by the extremely dense brush of golden-brown hairs on the metasomal S1, and by the flattened, spiniform projections on the mesothoracic venter in front of the mid coxae.
The male here designated as the lectotype bears a red label "Megachile / LECTOTYPUS / boliviensis / Fritz." Manfredo Fritz studied this speci- Diagnosis. The females are readily recognized by the flattened face with modified hairs on the clypeus and the supraclypeal area. The male also has a flattened frons, depressed well below the level of the compound eyes. Both sexes have a gibbous scutellum. The male mandible is elongate, with a truncate, somewhat incised second tooth, close to the first tooth and removed from the upper tooth, which is right angular (Schwimmer, fig. 46 in Mitchell, 1980). This type of mandible is distinctive for M. schwimmeri among Argentinean Dasymegachile, except for males of the species treated by Durante and Abrahamovich (2006) as M. schwimmeri, the mandible of which is quite similar. Durante and Abrahamovich (2006) redescribed in detail the females of M. schwimmeri, but they misidentified the males. This is evident when comparing their drawings of male terminalia with those of Schwimmer (in Mitchell, 1980, p. 91). The male specimens from Jujuy cited by Durante and Abrahamovich correspond to a different, probably unnamed, species of Dasymegachile. These specimens have the anterior tarsus with a white outer fringe of hairs, and the apical margin of T6 has broad, trapeziform paramedian projections (Durante and Abrahamovich, 2006: figure 11). Megachile schwimmeri is characterized by the anterior tarsus with black hairs not forming an outer fringe, and the apex of T6 has small, pointed paramedian projections. The record of M. schwimmeri for Rio Grande do Sul, Brazil (Viana & Alves dos Santos, 2002;Silveira et al. 2002, as M. golbachi) is most probably wrong and may correspond to M. una. In Argentina M. schwimmeri is not known to occur outside the Andean range, from moderate to high altitudes.

Distribution.
Argentina, provinces of