48 THE NORTH AMERICAN SPECIES OF DROSOPHILA. 
X. SYSTEMATIC ACCOUNT. 
SYSTEMATIC POSITION,,OF THE DROSOPHILINE. FLIES. 
The following represents the classification now current among most 
students of the Diptera: 
Class: Insecta. 
Order: Diptera. 
Suborder: Cyclorrhapha. 
Family: Muscide. 
Series: Muscide acalypterate. 
Subfamily: Drosophiline. 
Muscide (= Eumyiide, Myodaria, Oligoneura, Muscoidea, etc.). 
Antenne three-jointed, with an arista on the terminal joint; longitudinal veins never 
branched; not more than three posterior cells, of which none but the first is ever closed 
or narrowed at the wing margin; marginal and submarginal cells open; bristles present; 
empodia never large. 
The family is easily split into two main groups, as follows: 
1. Calypteree (Schizometopa). Squame large; front of male narrowed or 
eyes meeting in front; transverse suture of mesonotum complete. 
2. Acalypteree (Holometopa). Squame small; front of male rarely nar- 
rowed, eyes never meeting in front; transverse suture of meso- 
notum never complete. 
Further subdivision, especially of the Acalypterse, is very difficult. 
A number of groups (about 20 to 26 generally recognized) have been 
segregated as subfamilies, or families if the Muscide are treated as a 
superfamily. The exact definition of these groups is scarcely possible, 
as in so many cases there are forms that agree with one group in most 
of their characters, but are aberrant in other respects. Many keys 
are to be found, but none, I think, will bring all the forms to the 
groups where they are commonly placed. There are, scattered all 
through the Acalyptere, many genera of doubtful affinities. These 
are put in different subfamilies by each new student. Such forms in 
the neighborhood of the Drosophiline are Curtonotum, Apsinota, 
Aulacigaster, Paratissa, Stenomicra, Periscelis, Amphoroneura, and 
the forms near Asteva. In the present treatment the three first-named 
have been included in the subfamily, and the others have been excluded. 
This has been done largely as a matter of convenience. It seems 
impossible to get a classification into subfamilies that will be generally 
satisfactory. Certain forms obviously belong close together (e. g., in 
the present case, Drosophila, Scaptomyza, Chymomyza, Cladocheta, 
Mycodrosophila, Leucophenga, Pseudophortica, Zaprionus, Zygothrica, 
Camilla, and Stegana). Others are more or less like these, and may 
be included in the group or not, according to the personal equation 
of the individual student. I have excluded Paratissa because it seems 
to me more like the Ephydrine; and Asteia, Crepidohamma, Echid- 
