Canadian Journal of Arthropod Identification
 
 

A Review of the Species of Drosophila (Diptera: Drosophilidae) and Genera of Drosophilidae
of Northeastern North America

CJAI 31 -- June 7, 2017
doi:10.3752/cjai.2017.31

M.E. Miller, S.A. Marshall, and D.A. Grimaldi

| Abstract | Introduction | Checklist | Anatomy | Key to genera | Key to Drosophila species | Acknowledgments | References | PDF | Cite |
 
 

 

Introduction

The family Drosophilidae Rondani, some species of which are commonly called vinegar flies or lesser fruit flies, is a large, morphologically diverse, cosmopolitan group of acalyptrate flies. Adults are typically 1-6 mm long, yellow to black in colour, with or without bands or stripes on the abdomen and stripes or spots on the thorax. The wings are sometimes darkened or marked with dark areas, and the eyes are typically red in life (Wheeler, 1987).

The family Drosophilidae includes 73 extant and 3 extinct genera, encompassing over 3950 species (Brake & Bächli, 2008). With the exception of two genera of uncertain subfamily affinity, the family is divided into the subfamilies Steganinae (28 genera) and Drosophilinae (43 genera). The largest genus of Drosophilidae is Drosophila Fallén (1157described species). Drosophila species are found in all six biogeographic regions (Australasian, Afrotropical, Nearctic, Neotropical, Oriental and Palearctic), with the largest number found in tropical areas. Several hundred additional undescribed species probably remain to be discovered in tropical regions (Markow & O’Grady, 2006; Markow & O’Grady, 2007).

Drosophila has been an extremely important group for evolutionary biological research since the beginning of the twentieth century. It is one of the best-studied groups of organisms in modern biology in terms of its life history, biology, phylogeny, ecology, and especially genetics, largely attributed to the establishment of Drosophila melanogaster Meigen as the leading model system for genetic research. Approximately 500 species of Drosophila can now be easily reared and studied in a laboratory (Yassin, 2013), and the full genomes of many species have been fully sequenced, so the study of Drosophila has a firm comparative as well as experimental basis.

Seven secondarily widespread or cosmopolitan species of Drosophila are associated with human habitations (Ashburner et al., 1981). Most Drosophila, including the cosmopolitan species, lay eggs in decaying organic materials such as compost, overripe or rotting produce; others breed in live or decaying fungi, dung, slime or sap fluxes of trees, cacti, or flowering plants (Bächli et al., 2004; Carson, 1971; Markow & O’Grady, 2008). The Oriental species Drosophila suzukii (Matsumura) and Drosophila subpulchrella Takamori and Watabe are exceptional in that they oviposit in healthy whole fruit (Matsumura, 1931). Drosophila suzukii has recently spread beyond its native range to become an invasive, damaging and geographically widespread agricultural crop pest, now widely known as the “Spotted Wing Drosophila” (Hauser et al., 2009; Steck et al., 2009). This has resulted in a demand for new tools to identify and monitor D. suzukii and other potentially damaging invasive Drosophila species.

Identification Tools

The North American species of genus Drosophila are relatively well studied, notably by Sturtevant (1921), Patterson (1943), Patterson and Stone (1952) and Strickburger (1967). However, there are few identification keys specifically for Nearctic Drosophila species, in contrast to such references as Bächli et al. (2004) for the northern European species. Patterson’s (1943) key to the Drosophilidae of the southwestern United States is now out of date and cannot be used to identify all Drosophila species in the southwest or in other areas of North America. Moreover, that reference did not utilize the most important character system for diagnosing and identifying species: the male genitalia. M.R. Wheeler’s key in Greenberg’s (1971) Flies and Disease covers only the cosmopolitan and synanthropic Drosophila species. Strickberger’s (1967) key is not functionally effective for identification, since not all species are included, and the use of superficial characters fails to adequately distinguish several species. A key provided in Markow and O’Grady (2006) covers only the Drosophila species in the Drosophila Species Stock Centre at the University of California, U.S.A. This key includes numerous Nearctic Drosophila species, and although it is useful for specimens that can be reared in a laboratory, it excludes many species not currently in culture. Thus there are no current, complete keys to Drosophila species of all or a significant part of North America, and the northeastern North American fauna remains effectively unidentifiable.

Considering that northeastern North America is essentially the birthplace of Drosophila genetic research (Ashburner et al., 1981; Koehler, 1994), it is surprising that such a profound gap exists regarding the identification of Drosophila species naturally occurring in the region. The keys to the species of Drosophila and the genera of Drosophilidae offered here provide the identification tools to ensure early detection of invasive species such as D. suzukii, and will facilitate cost-effective and accurate identification of wild Drosophila species in northeastern North America.

Label data in this study, with collection dates from January to December, include records from rotting mushroom bait traps, from apple cider vinegar bait traps (in blackberry, blueberry, raspberry, sour cherry, grape and peach fields), from rotting organic materials (onions, grapes, bananas, grass piles and compost), from field sweeps, from a hog barn, from tree wounds, from tulip bulbs (originating from Holland), from damp birch & maple, and from indoor environments.

Notes

A list of literature records used in species distribution maps was obtained from publications in Gerhard Bächli’s TAXODROS database (Bächli et al, 2017); these sources are not listed in the materials examined.

Material Examined

Specimens were examined from the following institutions (Codens as in Arnett et al., 1993):

AMNH: American Museum of Natural History, New York, NY, USA
CNCI: Canadian National Collection of Insects, Ottawa, ON, Canada
DEBU: University of Guelph Insect Collection, Guelph, ON, Canada
MCZN: Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA
USNM: United States National Museum, Washington, DC, USA

Specimen data for all specimens examined are available from The Knowledge Network for Biocomplexity (doi: 10.5063/F11J97Q0).