McEvey: Drosophila setifemur species group 
35 
Figures 12-13. Antero ventral setation of fore-femora of Drosophila 
teratos and D. niveifrons. (72) Drosophila teratos, male, Lake 
Eacham, Queensland, AMS K233710. (13) Drosophila niveifrons, 
male, Wanigela, Papua New Guinea, AMS 234063. Scale 0.5 
mm (a niveifrons paratype [marked ex stock 14.x. 1979 Kitagawa 
et al .] in BPBM has 8-9 spinescent setulae, McEvey pers. obs. 
26.xi.2008). 
A variety of different terms have been applied to the 
spinescent setulae lying in a series along the lower anterior 
surface of the fore-femur, and there has been a tendency to 
emphasize only this aspect of the femoral setation, ignoring 
the taxonomically useful arrangement of long setae on the 
posteroventral surface. Reference is made, for example, to 
“short, stout, spine-like bristles on lower apical part of fore 
femora” (Patterson & Wheeler, 1942); “comb-like series of 
stout bristles on femur” (Mather, 1955); “row of ... short, 
stout, microscopic setae on the apical half of the anteroventral 
surface of the fore femur” (Clark, 1957); “fore femur with 
more or less well developed row of short stout comb-like 
teeth (femoral comb)” (Bock, 1976); “the comb-like bristle 
row on the inn er side of the first femur” (Wilson et al., 1969). 
It is only Malloch (1924) however, who made reference 
to the diagnostic utility of the setation on the posterior 
side of the fore-femur. Indeed it is the relative length and 
arrangement of long setae arising from the lower fore-femur 
on its posterior side that offers a more definitive means of 
separating species of the immigrans and setifemur species 
groups, at least in females. Males of D. setifemur completely 
lack serial spinescent setulae and have instead a thick brush 
of erect hairs (Fig. 3). 
When comparing Drosophila prodispar and D. setifemur, 
Parsons & Bock wrote that both “species show the same 
dimorphism in carina width and hypertrophy of the fore¬ 
femur. However, examination of the genitalia under the higher 
powers of a stereo microscope reveals diagnostic differences 
in both sexes. In the male, the aedeagus is cylindrical in 
dispar [= setifemur ] but broadly flattened in prodispar, a long 
slender curved finger-like process extending from the genital 
arch [sic] is visible on each side in dispar [= setifemur ], while 
the corresponding process in prodispar is shorter, wider 
and barely curved. In the female, the egg guide in dispar 
[= setifemur ] possesses a slender apical extension bearing 
fine teeth; in prodispar the egg guide possesses no apical 
extension and fine teeth are absent. These differences are 
evident in pinned specimens and should also be obvious in 
live flies” (Parsons & Bock in Bock, 1982: 53). As specimens 
of D. setifemur and D. prodispar examined by me in the AM 
have a distinctive extension of the cercus, not the genital 
arch, I believe the above reference to an extension of the 
“genital arch” (epandrium) is an error. Note also that sexual 
dimorphism in the width of the carina is rather subtle. 
The Drosophila setifemur species group 
Within the Drosophilidae, but not generally in the Diptera, 
there is an informal and hierarchical classification between 
the genus level and the species level. For example, the 
melanogaster “species group” accommodates a large number 
of species that share morphological characteristics with D. 
melanogaster (Bock & Wheeler, 1972; Bock, 1980) and are 
phylogenetically closely related (Lemeunier et al., 1986). 
The “species group” is a superspecific aggregation with a 
rank below subgenus, it is divided into various “subgroups”, 
subgroups are somet im es divided into “complexes”, and 
complexes into sibling pairs, cryptic species or other loosely 
defined groupings of small numbers of species. (Subspecies 
is a rank seldom used in the Drosophilidae.) Guidelines for 
the application of these subgeneric and superspecific names 
are not offered by the ICZN and so it is difficult to affect an 
objective re-appraisal of the so-called “dispar species group”, 
now that the correct name of the typical species is no longer 
D. dispar. There is also the untidy situation of synonymy 
with the “ dispar species group” in another drosophilid genus 
Zygothrica; this clash would be rectified if the Drosophila 
dispar species group was renamed. 
The logical course of action, and the one adopted here, 
is to replace the name “ Drosophila dispar species group” 
with the name “ Drosophila setifemur species group”. This 
is done in anticipation of confusion that might result were 
nothing done. In light of the current systematic uncertainties 
due to the polyphyletic assemblage of species in Drosophila 
(O’Grady & DeSalle, 2008) it would be premature 
to consider erecting a new genus or new subgenus to 
accommodate D. setifemur and D. prodispar although 
the atypical male terminalia (especially the acuminate 
extension of the lower cercus and the form of the ventral 
projections of the epandrium are quite unlike any other in 
the Drosophila subgenus Sophophora ) offers a suitable 
starting point for such a consideration. The typical species 
of the species group is D. setifemur, and D. prodispar is 
the only other member. Prior to the present investigation, 
however, it was generally accepted that the “ Drosophila 
dispar species group” had three species (e.g., Ashburner 
et al., 2005) viz. D. dispar [= setifemur ], D. prodispar 
and D. unguicula Okada & Carson, 1983:138. Okada & 
Carson (1983) speculated that D. unguicula from Papua 
New Guinea “seems to belong to the dispar [ =setifemur] 
species group” but the “cercus [is] with a strong black spur 
ventrally” and in this respect it is quite unlike D. setifemur 
which has instead a long acuminate process with subapical 
trichose hairs. Drosophila unguicula has not been examined 
in this study but in light of the description and illustrations 
offered by Okada and Carson and the detailed examination 
of the D. setifemur and D. prodispar genitalia in the present 
study, it is concluded that D. unguicula should be excluded 
from the setifemur species group. 
