Systematics and biology of Xylocopa subgenus Schonnherria (Hymenoptera, Apidae) in Argentina

Abstract Biological information on the species of the large carpenter bee Xylocopa subgenus Schonnherria occurring in Argentina is revised. Based on the appraisal of museum specimens, the study of type material, and field surveys conducted across 15 provinces between 2007 and 2011, the following seven species are recognized for the country: Xylocopa bambusae Schrottky, Xylocopa chrysopoda Schrottky, Xylocopa macrops Lepeletier de Saint Fargeau, Xylocopa simillima Smith Xylocopa splendidula Lepeletier de Saint Fargeau, Xylocopa pulchra Smith, and Xylocopa viridis Smith. Previous literature records of Xylocopa dimidiata Latreille, Xylocopa subcyanea Pérez, and Xylocopa varians Smith for the province of Misiones appear to have been misidentified specimens, although the presence of these species in Argentina cannot be entirely ruled out given the proximity of this province to Brazil and Paraguay where they occur; Xylocopa boops Maidl was described from a male specimen with unusually enlarged eyes and is newly synonymized under Xylocopa macrops. Males and females of all species are diagnosed, described, and figured, including details of the male genitalia. Taxonomic comments, data on the geographical distribution and nesting substrates, and identification keys to all Argentinean species of Schonnherria are provided. The nesting biologies of Xylocopa splendidula and Xylocopa viridis are documented.


Introduction
Large carpenter bees of the genus Xylocopa Latreille (Apidae: Xylocopini) are conspicuous, commonly encountered, and fascinating elements of the melittofauna in many regions of the world. These usually robust, large, hairy bees nest in solid wood including structural timbers or in dead stalks of plants (hence their common name), althought some species nest in the ground. The more than 470 species are currently grouped in 31 subgenera, and approximately 100 species (in 12 subgenera) are recorded from the Neotropical region (Ospina 2000;Michener 2007;Moure 2007). The social behavior of Xylocopa is interesting and still poorly studied. Some species may live solitarily while others in semisocial or primitively eusocial nests, where the oldest female (mother or sister) feeds via trophallaxis both young females and males. Variation among polulations in these social behaviors may occur (Michener 1990). The diversity of mating behaviors is another interesting aspect of the biology of Xylocopa. For example, males in some species exhibit a lek-like mating behavior, defending areas that do not contain resources and at which females are attracted via pheromones. In other species, males patrol nesting or foraging sites and intercept females at flight (e.g., Gerling et al. 1989;Vinson and Frankie 1990;Prager and Richardson 2012). The male morphological modifications associated with such a diversity of mating behaviors are also outstanding. They range from the enlargement of the compound eyes, distinctly modified legs with a number of spines and protuberances of diverse shapes and sizes (Lucia et al. 2014), to the development of large pheromonal glands that change the configuration of the mesosoma (Minckley 1994).
Carpenter bees are also economically important. Some species are effective pollinators of diverse crops, including passion fruit, squash, tomato, Brazilian nut tree, and eggplant, and they are already being used for this purpose in different countries (e.g., Keasar 2010;Giannini et al. 2015). Additionally, some species such as X. virginica (Linnaeus) in North America or X. frontalis (Olivier) in South America may become an annoyance for people when nesting in houses or buildings. First, the large body size, the loud buzzing produced when flying or making their nests, and the approching behavior exhibited by males when patrolling a mating site, make these bees intimidating. Second, the various nest entrances and tunnels built inside the timber deface and may also weaken the nesting timber, thus causing structural damage and requiring control (Barrows 1980).
Despite the interesting biology, ecological importance and potential for development in crop pollination, most species of Xylocopa remain both biologically and taxonomically unknown. As for other taxa , the diversity of Xylocopa is largely unexplored in many regions of the world and many species are difficult to nearly impossible to identify. Species from many areas are known only from the type specimen, a small number of specimes or from a single sex, the available descriptions do not allow for reliable identifications, and identification keys, when available, are poorly illustrated or not illustrated at all.
As part of an on-going effort to reduce such a taxonomic impediment and to increase our understanding of the biology of Neotropical carpenter bees, here we revise the species of Xylocopa subgenus Schonnherria Lepeletier de Saint Fargeau occurring in Argentina. This subgenus is the second most species-rich group of Xylocopa in the Western Hemisphere, containing about 30 species that range from southern United States to southern Argentina (Michener 2007). Here we recognized seven of the 11 species currently listed for the country (Hurd 1978); three of them appear to be records from misidentified specimens and one is placed in synonymy. We provide diagnoses, illustrations, descriptions, taxonomic comments, and information on the distribution to all species known to the country. This work is a continuation of a series of contributions dealing with the systematics and biology of carpenter bees in Argentina Ávalos-Hernández et al. 2011;Stuke et al. 2011;Lucia et al. 2012;Lucia and Gonzalez 2013;Lucia et al. 2014;Lucia et al. 2015).

Material and methods
Morphological terminology generally follows that of Hurd and Moure (1963) and Michener (2007). The use of ventroapical plate of the male gonocoxite and lateral carina of the penis valve follows Michener (1975) and Minckley (1998); supraorbital line refers to the upper ocular tangent and is used here to indicate the position of the laterall ocelli in frontal view. External morphological features were studied using a Nikon SMZ 745T stereomicroscope. Photographs were taken with a Canon Power Shot® A520 digital camera attached to a steromicroscope and images were assembled using CombineZM open software (Hadley 2011). Species redescriptions emphasize structural characters, such as punctation, and are based on the examined specimens to include possible variations among characters. Ten specimens of each species were measured, except for X. chrysopoda Schrottky and X. pulchra Smith from which we were only able to measure two specimens of each. Measurements were taken with an ocular micrometer and were rounded to the nearest tenth of a millimeter; mean values and ranges are given in millimeters. Total body length was measured from the head to the apex of metasoma in lateral view; forewing length was measured at the anterior margin, from the apex of the costal esclerite to the wing apex; mesosoma width was measured between the outer borders of the tegulae; metasoma width was measured across the second tergum. The following abbreviations are used in the descriptions: T, S, F, and OD for metasomal terga and sterna, flagellar segments, and maximum diameter of the median ocellus, respectively. Male genitalia were mounted on metal studs and coated with gold-palladium for examination with a scanning microscope (SEM) Jeol-JSM-6360MV.
The primary types of all species treated herein were examined, as well as a total of 1702 specimens from all provinces of Argentina deposited in the following institutions and personal collections. The curators who kindly arranged the loans or allowed access to the collection in their care are indicated parentheses:

BMNH
British Museum Natural History, London, UK (D. Notton) CZ Private Collection of "Caire-Zelich", Entre Ríos, Argentina (L. Caire-M. Zelich) Information on the distribution was taken from literature and from specimen labels. The biogeographic provinces referred in the distribution account for each species followed those of Cabrera and Willink (1980). Complete label data for the examined material are available as supplemental material [online only]. Label data were transcribed literally, with bars "//" indicating information recorded on different labels.

FAUBA
Surveys for specimens as well as for nests of Xylocopa were conducted by M.L. between 2007 and 2011 across 15 provinces. The following provinces could not be sampled: Formosa, San Juan, La Pampa, Neuquén, Rio Negro, Santa Cruz, and Tierra del Fuego. When nests were found, the following variables were recorded: type of substrate and location (dead wood, structural timber, etc), plant species, and height above ground. Adults found inside nests were collected, killed, and deposited as vouchers in MLP. In the laboratory, the internal nest architecture was studied using threedimensional molds made of liquid silicone rubber, as described in Lucia et al. (2014). Photographs of the nests were taken with a Panasonic® FZ18 digital camera.
Measurements of internal nest features were taken from the molds using a caliber. Mean values are provided with standard deviations. We used a Pearson correlation analysis to test for association between the following variables: tunnel length and tunnel width, total number of tunnels per nest and maximum diameter of the tree branch where the nest was found, total number of brood cells and total number of tunnels, and number of cells per number of tunnels and tunnel length. , with apical tooth about as broad as or broader than basal tooth; T1 with complete gradulus on both sexes, remaining terga with gradulus absent (except in the male of X. bambusae with gradulus also on T2); male genitalia with a large spine of the ventral margin of the gonocoxite and the apex of the gonostylus bifid.

Species accounts
Xylocopa bambusae Schrottky, 1902 Figures 1, 7, 13, 19, 25, 30, 35, 40, 57 Xylocopa bambusae Schrottky, 1902: 475  Diagnosis. The female of this species can be easily distinguished from other Argentinean species of Schonnherria by the following combination of characters: small body size (body length 14-17 mm); integument dark brown to black throughout, without metallic highlights; clypeus flat in profile, not elevated from adjacent paraocular area; clypeoalveollar distance long, about twice as long as longitudinal diameter of antennal socket; frontal carina projected into a distinct tubercle just above or at the upper tangent of anntenal sockets (Fig. 1); vertex and metasomal terga with large impunctate areas (Fig. 13); wings dark brown with weak coppery highlights basally, violet distally. The male can be easily recognized by the following combination of characters: small body size as in the female; body pubescence long, dense (obscuring integument in most areas), yellowish to reddish brown; supraclypeal area with a distinct tuft of long, erect, dense setae obscuring integument (Fig. 7); T1-T5 dark reddish brown, each with a distinct, broad, median yellow maculation on disc, sides and distal margins (inmaculate areas) densely covered by long, dense dark brown setae (Fig. 19). The female of this species superficially resembles X. splendidula and other small species of Schonnherria such as X. lucida Smith and X. muscaria (Fabricius) (not occurring in Argentina); however, those species have distinct metallic blue highlights on the body as well as different patterns in the punctation, pubescence, and wing coloration. The supraclypeal tuft of setae and pale maculations on the metasomal terga of the male of X. bambusae are so distinctive and unique among species of Schonnherria that these characters have been used to justify its recognition in a different subgenus.
Male. As in the female, except for usual secondary sexual characters and as follows: body length 15.9 (15.0-16.7); head length 3.5 (3.5-3.6); head width 4.4 (4.4-4.6); mesosoma width 6.3 (6.0-6.6); metasoma width 6.6 (6.0-7.0); forewing length 11.6 (11.0-12.7); forewing width 3.6 (3.4-3.8). Coloration. Cream to yellowish maculations as follows: labrum, mandible basally, clypeus, supraclypeal area, paraocular area (except on upper one-third), anterior surface of flagellum ( Fig. 7), outer surface of profemur basally, outer surfaces of protarsi, and discs of T1-T6 (maculations narrower on apical terga, sometimes absent on T4-T6) (Fig. 19). Wings subhyaline, yellowish with faint coppery highlights. Pubescence. Longer, denser than on female, yellowish to reddish brown, darker on face, vertex, sides of mesoscutum, mesoscutellum, metanotum, and inmaculate areas of terga (Fig. 19); supraclypeal area with a distinct tuft of long, erect, dense setae obscuring integument (Fig. 7); discs of mesoscutum and mesoscutellum asetose; maculated areas of terga with scattered erect setae. Sculpturing. Vertex and gena more densely punctate than in female, punctures separated by 1-2 times a puncture width; tegula impunctate, smooth and shiny on disc, otherwise dull, punctate (1-2 times a puncture width). Metasomal terga densely punctate (a puncture width or less) on inmaculated areas, including distal margins; punctures scattered on maculated areas. Structure. Middle interocular distance 2.0-2.1; distance between median ocellus and posterior margin of vertex 2.2-2.9 OD; orbitoccipital distance 0.4-0.6; interocellar to ocelocular distance 2.3-3:1; interocellar to ocelloccipital 1.2-1.4:1; ocellocular to alveolocellar 0.2-0.4:1; orbitoccipital to ocellocular 1.7-2.2:1; alveolocular to interalveolar 0.8-0.9:1; clypeoalveolar distance 1.5× longitudinal diameter of antennal socket; clypeocellar distance to distance between median ocellus and posterior margin of head 1.3-1.6:1; frontal carina strongly elevated, short 0.7-0.8, not tuberculiform as in female; clypeus broader than long, 1.5-1.6:1; proportion of length of scape, pedicel and F1-F4: 2.5-2.7:0.3-0.4:1:0.4:0.4:0.4. Mesoscutellum nearly flat, exposed, along same inclined plane with metanotum and base of propodeum; protrochanter with distinc spine; ventral surface of metatrochanter and metafemur basally glabrous, distinctly protuberant. Genitalia as in Figs 25,30,35,40. Distribution. This species is also known from Brazil and Paraguay (Table 1). In Argentina it has only been recorded from the province of Misiones, which is included in the Paranaense biogeographic province (Fig. 57). Comments. Hurd and Moure (1961: 186-187) designated a male and a female syntype as the lectotype of X. eburnea and X. bellula, respectively. In both cases Hurd and Moure (1961) unambiguously selected a specimen, provided information on the label data and repository collection, and clearly designated it as the sole name-bearing specimen, thus complying with the ICZN, Article 74. Such lectotypes designations appear to have been missed by Moure (2007: 673) who indicated syntypes for both species. The lectotype designation is valid for X. eburnea because Friese clearly mentions the existence of several males and females in the original description. However, the lectotype designation is unnecessary for X. bellula because Bréthes indicated a single female in the original description, which is currently housed at MACN. This specimen has a locality label that reads "Misiones, XII-1911, Abel Muniez", a label in Bréthes' handwriting and a holotype label [probably added recently]. Two other females, each bearing a locality label that reads "Misiones", are also found with that specimen; one of them bears a lectotype label. Perhaps because of the additional two specimens, Moure and Hurd (1961) thought of them as syntypes and designated as lectotype the female collected on 1911. Curiously, the lectotype label is not found in that specimen but in one of the two additional females. To avoid further confusion, we added a red label with the following note to the type: 'This is the true type as indicated in Bréthes' Despite actively searching for nests as well as specimens of this species in insect collections and in the field, the only specimens available to us were those collected by Peter Jörgensen at different times of the year in Misiones during the first decade of   Hurd (1978), Moure (2007), and Montalva et al. (2008).

General distribution Distribution in Argentina
Altitude ( 1900 (see supplemental material). The species has not been collected ever since. The nesting biology of this X. bambusae is unknown, although it presumably nests in bamboo stalks (Schrottky 1902).
Comments. Schrottky (1912) suggested that X. chrysopoda may be the male of X. pulchra, a species currently known from the female sex. As for X. bambusae, these two species are rarely collected and are currently known from a limited number of specimens. We did not collect nor examine specimens of X. chrysopoda from Argentina captured in the last 100 years. Diagnosis. The female of this species can be distinguished from other Argentinean species of Schonnherria by the following combination of characters: medium-sized bees (18-22 mm); body pubescence black; integument black throughout with very weak metallic blue, often most evident on mesoscutum, tegula, outer surfaces of proand mesotibiae, and metasomal terga; clypeus depressed basally on disc, dorsolaterally elevated from adjacent paraocular area (Fig. 2); vertex, behind lateral ocelli, with coarse punctures separated by 1-2 times a puncture width; metasomal terga sparsely punctate, punctures coarse and separated by at least two times a puncture width (Fig. 14); wings black with metallic green and violet highlights. The male can be easily recognized by the following combination of characters: compound eyes enlarged, strongly convergent dorsally (Fig. 9); meso-and metasoma with distinct metallic blue highlights; metasoma sparsely punctate with very short setae, each seta barely exiting puncture; discs of S2-S6 each with sublateral yellow maculation. The female of this species superficially resembles that of X. simillima and X. dimidiata Latreille (not occurring in Argentina, see below) in the body size and black color of the integument, pubescence and wings. However, it can be separated from both species primarily by the midbasal tubercle of the labrum and the shape of clypeus. In those species the labrum has a single, large, capitate tubercle and the disc of the clypeus is flat. In X. macrops the labrum has three tubercles, a longitudinally elongated median tubercle and two small sublateral tubercles, and the clypeus is basally depressed, dorsolaterally elevated from adjacent paraocupar area. The male can be confused with that of X. splendidula by the compound eyes strongly convergent dorsally and the blue metallic highlights of the metasoma. However, in X. macrops the metafemur is distinctly modified, with the ventral margin strongly protuberant, the metabasitarsus is robust and shorter than the metatibia. In X. splendidula both the metafemur and metabasitarsus are unmodified, and the latter is longer than the metatibia; also, yellow maculations are absent from the labrum and discs of the sterna (present in X. macrops).
Comments. Maidl (1912) described X. boops based on a single male from an unspecified location in Brazil. The species was later listed by Hurd (1978) from Tafi, Province of Tucuman, Argentina. We examined the type specimen currently deposited at NMW (Figs 49-52) as well as the male specimen from Argentina deposited at USNM. Both specimens closely agree with X. macrops in all morphologically external characters, including the genitalia, except by the size of their compound eyes. In these specimens the eyes are extremely large and convergent above so that their upper margins are nearly in contact dorsally (Figs 49, 50). Such upper interorbital distance is about 0.23 times OD in the type of X. boops whereas it ranges from 0.54-0.72 times OD in specimens of X. macrops (n = 10). The shapes of the gonocoxite, apex of gonostylus, and lateral carina of the penis valve, which have proven to be reliable in species recognition in Schonnherria (Figs 25-44), are identical between X. boops and X. macrops. Thus, it seems to us that X. boops was described from an individual of X. macrops with unusually large eyes and we have decided not to recognize this species.
Here it is synonymized under X. macrops. Hurd (1978: 25) listed X. subcyanea Pérez from Misiones and Torreta et al. (2010) from Paraná, province of Entre Rios. We were not able to capture or find any specimen of this species from Argentina in the field or in the collections we visited. However, a single female of X. macrops deposited at MACN and labeled "Paraná, Noviembre, n° 190", was erroneously identified as X. subcyanea. Likewise, the two female specimens recorded by Torreta et al. (2010) as X. subcyanea (deposited at FAUBA) turned out to be X. macrops. Thus, it appears that records of this species for Argentina are misidentified specimens. We examined the type of X. subcyanea currently deposited at MNHN and also examined specimens of this species from Brazil. The female of X. subcyanea can be distinguished from that of X. macrops by the upper gena densely punctate (largely impunctate in X. macrops), disc of clypeus flat, uniformly punctate (largely impunctate and depressed basally in X. macrops), punctures of terga elongate, dense (punctures circular and sparse in X. macrops), and wings subhyaline, brownish (dark brown to black in X. macrops).
Male. Unknown Distribution. Hurd (1978: 23) listed this species from Brazil, Paraguay, possibly Colombia, and the provinces of Misiones and Salta in Argentina (Fig. 58). It occurs in the Paranaense biogeographic province (see comments below).
Comments. Xylocopa pulchra is known only from the female, and the male of X. chrysopoda may be conspecific with this species, as suggested by Schrottky (1902). As for X. bambusae and X. chrysopoda, this species is rare in collections, and it has not been captured in the last 65 years. In addition to the type, we were only able to examine a historical specimen from Misiones deposited at MLP and specimen from Pocitos, Salta, deposited at USNM. The presence of this species in Colombia needs to be confirmed (Gonzalez et al. 2009 Diagnosis. The female of this species can be distinguished from other Argentinean species of Schonnherria by the following combination of characters: large body size (body length 20-23 mm); labrum basally with a distinct, large, single capitate tubercle about as large as median ocellus; integument dark brown to black throughout, with basal three or four terga often with distinct broad, light reddish brown bands on discs (rarely orange) (Fig. 16); metasomal terga with punctures circular to ovoid, sparsely punctate on discs of basal terga (2-4 times a puncture width), punctures denser laterally and on apical terga; discs of basal terga with very short, black, simple setae, each seta barely exiting puncture, setae increasing in length laterally and on apical terga. The male can be easily recognized by the combination of compound eyes strongly convergent dorsally (Fig. 10), metasomal terga dark brown to black with basal terga light reddish brown on discs, and wings dark brown.
Comments. Brèthes' original description of X. rotundiscuta was based on three females. To stabilize this name, Hurd and Moure (1961: 191) unambiguously designated one of the syntypes as the lectotype. This specimen, deposited at MACN, has a locality label that reads "Misiones", a catalogue number 7597 [misinterpreted by Hurd and Moure as 2597], a handwritten number 765 [interpreted by Hurd and Moure as 753], and a lectotype label. Such a valid designation appear to have been missed by Moure (2007: 668). Figures 5,11,17,23,28,33,38,43,56 Xylocopa splendidula Lepeletier de Saint Fargeau, 1841: 190 (holotype: ♀, Brazil, whereabouts unknown, see comments below) Xylocopa (Schonnherria) splendidula: Hurd and Moure 1963: 123. Diagnosis. Both sexes of this species can be distinguished easily from other Argentinean species of Schonnherria by the following combination of characters: small to medium body size (body length 13-19 mm); body pubescence entirely black in the female, in the male with dense off-white pubescence on mesepisternum, tegula anteriorly, sides of mesoscutum and mesoscutellum, and dorsum of T1; meso-and metasoma with distinct metallic blue highlights; wing membrane subhyaline with weak violet highlights; male compound eyes enlarged, dorsally convergent, with upper margins separated by at least 2.7 times OD (Fig. 11); and hind leg of male unmodified, except by metatibia with long, slender subapical projection on inner margin, similar in size and thickness to tibial spur. This species can be confused with X. macrops, particularly the male, by the compound eyes distinctly convergent dorsally, metasoma with metallic blue highlights, off-white pubescence on mesosoma and T1, and wings subhyaline. However, in X. macrops the compound eyes are larger and closer dorsally (0.54-0.72 times OD) than in X. splendidula and the hind leg is distinctly modified, with coxa and trochanter each bearing a tooth or spine, femur strongly protuberant ventrally, tibia with two large subapical spines on its inner margin, and basitarsus robust, shorter than the tibia (slender and longer than tibia in X. splendidula). In addition, the labrum is yellow and the metasomal sterna are maculated in X. macrops (labrum and metasoma inmaculate in X. splendidula).
Comments. Lepeletier de Saint Fargeau (1841) described this species based on a female specimen from Brazil, which is presumably deposited at MNHN as indicated in the original publication. We received a female specimen from the MNHN identified as the type of X. splendidula. The complete label data for this specimen are as follows: "Museum Paris-EY0000001755 // Type ? [red label] // del` emb. del` Uruguay jusquiana missions [handwritten-round label] // splendidula [handwritten]". Because this specimen was collected in Uruguay, not in Brazil, it is not the true type of X. splendidula. We also examined from the same museum three specimens of X. splendidula from Brazil, but the label data do not agree with those indicated in the original description. Therefore, the whereabouts of the type of X. splendidula are currently unknown.
Comments. Xylocopa viridis, ranging from southern Mexico to Argentina, appears to be composed of multiple species. An appraisal of museum specimens under X. viridis deposited at SEMC from locations across its distribution range revealed considerable variation in body pubescence, punctation, body size, and shape of the apical projection of the inner surface of the male metatibia. A similar case seems to occur in X. varians Smith, a species with metallic green highligths that has also been recorded from Misiones and presumably confused with X. viridis. We studied the male holotype of X. viridis and the female type of X. varians, both from Brazil, as well as specimens of both species from Brazil and other countries in South America. We observed that both sexes of X. varians can be distinguished from those of X. viridis primarily by the terga with black setae on their discs (yellowish in X. viridis) and the upper gena of the female densely punctate, with a narrow impunctate band behind the outer margins of the compound eyes (upper gena sparsely punctate and with broad impunctate band behind outer margins of compound eyes in X. viridis). We found a female and male specimen from Misiones, both identified by P.H. Hurd as X. varians. These specimens are deposited at MACN and SEMC respectively, and their complete label data are as follows: "7596" // Misiones // 766 // Xylocopa varians Smith,P.H. Hurd 59 (MACN); "Misiones, Pindapoy, II-1956 // SEMC 1232909". Both specimens agree with the characters listed for X. viridis and thus the record of X. varians for Argentina appear to be based on misidentified specimens.
Specimens of X. viridis from Argentina and southern Brazil also seem to be different from those of northen Brazil, particularly in the length of the setae on metasomal terga, the color of tegulae, and the shape of the apical projection on the inner surface of male metatibia. Such differences are suggestive of a distinct species and further studies are needed to determine the species limits of X. viridis.
As in other species of Xylocopa (e.g., Camillo and Garófalo 1982;Gonzalez et al. 2009, Lucia et al. 2014), nests of both species were built inside dead, dry wood, and consisted of a single entrance connected to a system of branched tunnels through a vestibule (Figs 59-62). The tunnels were parallel to the wood grain with the barrel-shaped brood cells built at the end of each tunnel, which were separated from each other by partitions of sawdust. These partitions were thinner in the center, smooth and concave on their outer surfaces, but coarse and flat on their inner surfaces. In both species the length of the tunnel was not significantly correlated with its diameter (Pearson correlation coefficient, X. viridis: r = 0.15, p = 0.28; X. splendidula: r = -0.17, p = 0.31), and the number of tunnels per nest was not significantly correlated with the diameter of the branch where the nest was found (X. viridis: r = 0.57, p = 0.08; X. splendidula: r = 0.064, p = 0.94). The total number of brood cells varied among nests and species (Table 2) and it was significantly correlated with the total number of tunnels per nest (X. viridis: r = 0.96, p < 0.05; X. splendidula: r = 0.99, p < 0.05), but independent of the diameter of the branch (X. viridis: r = 0.60, p = 0.09; X. splendidula: r = 0.07, p = 0.93); the number of cells per tunnel was independent of the length of the tunnel (X. viridis: r = 0.37, p = 0.08; X. splendidula: r = 0.13, p = 0.46). Dimensions of some features of the nest of both species are indicated in Table 2. The number of adult females present at the time of collection ranged from one to six in nests of X. viridis (x= 2.3 ± 1.8) and from one to four in nests of X. splendidula (x = 2.7 ± 1.2); adult males were found only in three nests of X. viridis (x = 2.0, 1-3, ± 1.0) and in one nest of X. splendidula (7 males). Females were not dissected to examine the ovarian development or the presence of sperm in their spermatheca. Three females and one male of X. viridis were found dead inside the nest and were parasitized by the conopid fly Physocephala sp.; likewise, P. wulpi Camras was found parasitizing adults of X. splendidula (Stuke et al. 2011).

Discussion
The presence of seven of the 11 species of Xylocopa (Schonnherria) recorded for Argentina by Hurd (1978) are confirmed. One of the four remaining species, X. boops, is known only from the type and appears to have been described from a male specimen of X. macrops with unusually large compound eyes. Thus, here it is interpreted as synonym of that species (see species account). The remaining three species, X. dimidiata, X. subcyanea, and X. varians, occur in Brazil and Paraguay and were recorded from Misiones, a province that shares borders with both countries. We did not find any specimens of these species collected in Argentina nor did we capture any of them during the field surveys in Misiones or in any other province of the country. However, we examined a few female specimens of X. simillima, X. macrops, and X. viridis from Misiones that had been identified under those names (see species account). Thus, such records of X. dimidiata, X. subcyanea, and X. varians for Argentina seem to have been misidentified specimens. Yet, we still do not rule out entirely the possibility that these species existed or still exist in Misiones because of the proximity of this province to Brazil and Paraguay, and because three other species, namely X. bambusae, X. chrysopoda, and X. pulchra, were collected in Misiones during the early 1900's and have not been collected since.
Only two of the seven species of Xylocopa (Schonnherria) occurring in Argentina are widely distributed in the country. Xylocopa splendidula exhibits the widest range, found everywhere except in Tierra del Fuego and Santa Cruz (Fig. 56), while X. macrops occurs across the northwest, from Tucumán to Jujuy, and across the east, from northern Buenos Aires to Misiones (Fig. 55). Both species are abundant and frequently found in open fields and urban habitats. The remaining species have been recorded only from Misiones (Figs 57, 58). These species appear to occur across the Paranaense biogeographic province or Interior Atlantic Forest, an ecoregion that consists mostly of rainforests and encompases Misiones, eastern Paraguay, and southeastern Brazil (Cabrera and Willink 1980;Giraudo et al. 2003). Thus, Misiones seems to be at the border of their distribution.
In this study we were able to recognize a number of structural characters in both sexes that seem reliable in species recognition, such as size, shape, density, and distribution of punctures, length, density and type of setae, male sexual secondary modifications (projections of legs, particularly on inner surface of metatibia), and features of the male genitalia. Althought some of these characters have been mentioned by some authors, to date, an emphasis has been made to use patterns of coloration of wings and pubescence (e.g., Schlindwein et. al. 2003). We have made an effort to document and illustrate these structural characters and to them in the keys as well as in the diagnoses and descriptions. Distinctive characters of the genital capsule of the male include the shape of the medial margin of the gonocoxite in dorsal view (Figs 25-29), shape of the ventroapical plate (Figs 30-34), thickness of the penis valve and shape of the lateral carina of the penis valve, and pubescence of the apex of the gonostylus (Figs 35-44, 47, 48). For example, in X. splendidula the ventroapical plate has a well developed, nearly digitiform posteromedial lobe (Figs 33, 43) whereas it barely projects in X. chrysopoda (Figs 31, 41); in X. macrops the penis valve, in dorsal view, is robust and basally broad (Fig. 37) whereas it is slender across its length in X. viridis (Fig. 39); in X. chrysopoda the lateral carina of the penis valve is short and projects into a lobe (Fig. 36) whereas in X. splendidula it is longer, extending towards the apex of the penis valve (Fig. 38); in X. viridis both lobes of the apex of the gonostylus are densely covered by long, plumose setae (Figs 39,44) whereas in X. macrops the inner lobe is asetose and the outer is sparsely covered by simple setae (Figs  37, 42). These characters may also prove to be useful in future phylogenetic analyses.
The nesting biologies documented here for X. splendidula and X. viridis agree with those of other species of the genus that nest in solid wood, including species of Schonnherria (e.g., Jörgensen 1909;Bertoni 1911;Strand 1912;Gonzalez et al. 2009;Lucia et al. 2014). In addition to the nesting substrates recorded in this work, nests of X. splendidula have been found in dead wood of the following species: Populus piramidalis (Salicaceae), Arundo donax (Poaceae), Salix sp. (Salicaceae), Populus sp., Melia azedarach (Meliaceae), and Broussonetia papyrifera (Moraceae) (Holmberg 1884;Friese 1908;Jörgensen 1909;Telleria 2000). Such a wide range of plants used as nesting substrates in X. splendidula contrast with that of X. viridis, in which all 10 nests were found using the same plant species (Hovenia dulcis, Rhamnaceae). For both species, the number of cells per nest was significantly correlated with the number of tunnels, and both variables were independent of the diameter of the branch; likewise, the number of cells per tunnel was independent of the length of the tunnel. Thus, the observed variation among nests is probably due to ontogenic differences rather than substrate limitations, as suggested for other species (e.g., Camillo and Garófalo 1982). The same ontogenic differences could also explain the variation in the number of adult females found among nests.
The province of Misiones contains the highest diversity of large carpenter bees in Argentina (Lucia et al. 2014) and future conservation efforts as well as comparative bionomic studies on this group should be focused on this area. We do not know if the same pattern of diversity occurs in other groups of bees, but Misiones is an area well known to contain a high diversity of other organisms, including birds (e.g., Rabinovich and Rapoport 1975;Giraudo et al. 2003).

Males
Note. The male of X. pulchra is unknown.