The male terminalia of seven species of Drosophila endemic to the New World are described or redescribed and illustrated: one in the hydei subgroup (D. guayllabambae) and four in the mulleri subgroup (D. arizonae, D. navojoa, D. nigrodumosa, and D. sonorae) of the repleta group; one in the sticta group (D. sticta) and one so far unassigned to group (D. comosa). The D. guayllabambae terminalia redescription is based on a wild-caught fly. The redescriptions of the terminalia of the four species in the mulleri subgroup are based on strain specimens, while those of D. sticta and D. comosa terminalia are based on their holotypes. D. guayllabambae seems to be a strictly mountainous species of the Ecuadorian and Peruvian Andes. D. nigrodumosa is apparently endemic to Venezuela, occurring in the Andes as well as at lower altitudes. The remaining five occurs only at lower altitudes of the American continent. The detailed line drawings depicted in this paper aim to help interested taxonomists to tell those species apart. Their precise identification is of great importance to the knowledge of the American biodiversity increasingly threatened by human activities.

Drosophila subgenus, Drosophilinae , line drawings, Nearctic Region, Neotropical Region

Since early last century, the male terminalia have been the main feature used by entomologists to identify sibling species of insects, including flies of the genus Drosophila. Having this in mind, during the past forty years I have dedicated myself to clarify the identity of dozens of species of Drosophila mostly endemic to the American continents. Several line drawings of male terminalia prepared during this period have already been published (e.g. Vilela and Sene 1977, Vilela 1983, Vilela and Bächli 1990, Vilela et al. 2008). These were meant, in part, to complement those previously published by other authors (e.g. Duda, 1927, Wasserman 1962). Drawings of some species treated in the present paper were already published in the last 30 years by different authors (Rafael and Arcos 1988, Fontdevila et al. 1990, Ruiz et al. 1990, Heed and Castrezana 2008), although depictions of male sclerites in different views were offered.

In addition to specimens deposited in the Drosophila type and reference collection (DTRC) curated by Dr. Marshall R. Wheeler, all species strains belonging to the Drosophila repleta group formerly maintained at the University of Texas at Austin were examined in 1979. At that time, the author described the male terminalia of four undescribed species in his PhD thesis (Vilela 1981). However, for different reasons, they were not included in the resulting article entitled “A revision of the Drosophila repleta species group (Diptera, Drosophilidae)” by Vilela (1983). These four species are as follows: D. arizonae Ruiz, Heed & Wasserman, 1990, D. navojoa Ruiz, Heed & Wasserman, 1990, D. nigrodumosa Wasserman & Fontdevila in Fontdevila et al., 1990, and D. sonorae Heed & Castrezana, 2008.

Yet in 1979, the author also examined the spot-thoraxed female holotype of Drosophila peruensis Wheeler, 1959 in the DTRC, collected in 1903 somewhere along the Urubamba River, Peru. Based on the wing pattern and the morphology of the arista, the author proposed to transfer it from the repleta species group to the guarani species group (Vilela 1983). In late February 1984, the author searched for a male specimen of Drosophila peruensis making a visit to the Urubamba Canyon at the end of the railroad track (Fig. 1) running from Cuzco to Machu Picchu (km 112). This final station is located just above the bridge crossing the Urubamba River (Reparaz 1984: 197, 201) at the beginning of the unpaved zigzag road (Hiram Bingham) going up to the Machu Picchu ruins (ca. 2400 m altitude; Fig. 2A). One banana-baker’s yeast-baited trap was placed on the rocks at 1 km northeast of the Machu Picchu station (13°09'S; 72°32'W) alongside the railroad (km 111, Fig. 2B). On March 2^nd seventeen specimens (6 males, 11 females) of an undescribed species were collected and later misidentified and redescribed (Vilela and Pereira 1985, Vilela and Bächli 1990: 78) as D. peruensis. Nine years later, the previously misidentified and redescribed Peruvian specimens were renamed by Vilela and Pereira (1993) as Drosophila urubamba, included in the guarani group, and D. peruensis was transferred to a new group of its own (Ratcov and Vilela 2007). Additionally, one Drosophila male belonging to an undescribed species of the hydei subgroup of the repleta group was collected in the same trap and date. The specimen was dissected and its terminalia illustrated. This latter species would be formally described four years later (Rafael and Arcos 1988) as Drosophila guayllabambae based on specimens sampled from an isofemale line established from a single gravid female collected at 2200 m altitude in Ecuador.

Figure 1. 

Urubamba Canyon (as seen from Machu Picchu ruins), Department of Cuzco, Peru. III.1984, C.R. Vilela phot. Arrow points the final stop of the railroad at km 112 marker (Estación Ferrocarril de Machu Picchu, that no longer exists).

Figure 2. 

Collection sites C49 (13°09'S, 72°32'W) and C50 (13°09'S, 72°32'W): Urubamba Canyon, Department of Cuzco, Peru. A, (C49) 1 km S of the final stop of the railroad, 01.III.1984, C.R. Vilela phot. B, (C50) 1 km NE (at km 111) of the final stop of the railroad, 02.III.1984, C.R. Vilela phot.

In December 1985 and February 1989, aiming to clarify the identity of some poorly known American Drosophila other than those belonging to the repleta group, the author received two type specimens from the National Museum of Natural History (NMNH), Smithsonian Institution, Washington, D.C., USA. These included a male holotype of Drosophila sticta Wheeler, 1957 (from Honduras), belonging to the sticta group, and a male holotype of Drosophila comosa Wheeler, 1968 (from Costa Rica), an ungrouped species. These were dissected and their terminalia described or redescribed and illustrated but never published.

The purpose of this paper is to clarify the identities of seven of the American Drosophila species cited above, five of them (members of repleta group) apparently associated with rotting cacti.

Male specimens belonging to seven American species of Drosophila were analyzed and had their terminalia illustrated. The dissected specimens, in alphabetical order, are as follows.

Drosophila arizonae, two males from strain E2.2 (Navojoa, Sonora, Mexico); D. comosa, male holotype (Golfito, Costa Rica); D. guayllabambae, one male double mounted (1 km NE of Machu Picchu railroad station); D. navojoa, two males from strain E2.1 (Navojoa, Sonora, Mexico); D. nigrodumosa, two males from strain 514.8 (Mérida, Venezuela); D. sonorae, two males from strain E37.5c (Alamos, Sonora, Mexico); D. sticta, male holotype (Lancetilla, Honduras).

The nine non-type specimens were either collected by the author in Peru (the fourth one) or obtained in 1979 from stocks maintained in the National Drosophila Species Resource Center (NDSRC), originally at the Department of Zoology, University of Texas (Austin). The NDSRC is currently named Drosophila Species Stock Center of the University of California at San Diego, which is on the way to be moved to Cornell University in New York.

The following non-dissected specimens were also sampled simultaneously from the same stocks: D. arizonae (22 ♂♂, 36 ♀♀), D. navojoa (23 ♂♂, 14 ♀♀), D. nigrodumosa (3 ♀♀), and D. sonorae (8 ♀♀).

All double-mounted non-type specimens cited above are deposited in the Museu de Zoologia da Universidade de São Paulo, São Paulo, SP, Brazil (MZSP).

Additionally, four double-mounted specimens (1♂, 3♀♀) sampled from each of the three Mexicanstocks and from the Venezuelan strain maintained in the NDSRC were originally deposited in the DTRC (at the University of Texas, Austin) and later transferred to the AMNH (American Museum of Natural History, New York).

The analyzed and dissected type material includes the male holotypes of the poorly known Drosophila comosa and Drosophila sticta, both housed in the collections of the National Museum of Natural History, Washington, D.C., USA (NMNH).

Dissections of terminalia were performed following Wheeler and Kambysellis (1966), as modified by Kaneshiro (1969). For morphological terminology, measurements, indices, preparations of microscope slides as well as illustrations refer to Vilela and Bächli (1990, 2000) and Bächli et al. (2004). All line drawings in the same plate were drawn to the same scale.

The morphology of the male terminalia harbors highly informative and thus widely used characters for species identification and delineation. The detailed line drawings of the morphology of seven American species depicted here aim at facilitating the identification of these species. In turn, I discuss the implications of these line drawings, the systematics positioning of certain species and give additional comments on the species’ distribution range.

The detailed analyses of the male terminalia of selected seven American species of the genus Drosophila depicted here reinforce the idea that the knowledge of their component sclerites are essential to reliably tell closely related species apart. Although the terminalia of the Peruvian specimen of D. guayllabambae depicted in this paper slightly differ from those illustrated by Rafael and Arcos (1985) for the Ecuadorian holotype, the two specimens are considered to belong to the same species. The differences may be due to both intraspecific variation and different interpretation of the sclerites given by different authors. This species seems to be a strictly mountainous species of the Ecuadorian and Peruvian Andes, while the remaining six analyzed species occur at variable altitudes of the American continent.

This paper is a tribute to my great master and friend Gerhard Bächli in recognition for his Herculean efforts to create and manage TAXODROS, the indispensable database for anyone working on Taxonomy of Drosophilidae, and for his remarkable devotion to the Mitteilungen der Schweizerischen Entomologischen Gesellschaft as Editor-in-Chief during the past 22 years.

I am indebted to Dr Fabio de Melo Sene for his friendship, teaching and support during my undergraduate and graduate studies, to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) for fellowships and grants, to Dr John R. Elisson, Dr Marshall R. Wheeler, Mrs Marietta A. Reveley and Mrs Sarah K. Barron, for providing facilities during my visit to the Department of Zoology, University of Texas at Austin, to Dr Wayne N. Mathis from the National Museum of Natural History (Washington, D.C., USA) for loaning the holotypes of Drosophila comosa and D. sticta, and to Dr Luisa V. Pilares G., Dr Jaime A. Vásquez E. and Dr María del Pilar Suyo T. for the hospitality during my visit to the Universidad Nacional Mayor de San Marcos, Lima, Peru. Also, to Miguel Molina Napurí for the friendship and for gifting me the Reparaz Guide, to Dr Francisca Carolina do Val and Dr William W.M. Steiner for the critical reading of the manuscript, as well as Dr Gerhard Bächli, Dr Jan Máca and the subject editor MSc Patrick Rohner for corrections and suggestions that improved the submitted manuscript.