ANATOMY. 



29 



Drosophila, but present in Curtonotum, Stegana, Leucophenga, and other 

 genera. 



The dorsocentral bristles lie in longitudinal rows of hairs, and in 

 some forms, such as Drosophila funehris, D. repleta, and D. hydei, a 

 few of the hairs in this row anterior to the true dorsocentrals are some- 

 times enlarged and bristle-like. 



Between the dorsocentral rows are several rows of acrostichal hairs. 

 The number of these rows is a very convenient taxonomic character. 

 Unless otherwise stated, the count is to be taken just in front of the 

 anterior dorsocentral bristles. Some such convention is made neces- 

 sary by the fact that the rows are often a little irregular, and are apt 

 to be more numerous in the anterior part of the region than in the 

 posterior. 



LEGS. 



Each leg consists of nine segments or "joints": the coxa, trochanter, 

 femur, tibia, and five tarsal joints. The coxa, or basal joint, is articu- 

 lated to the thorax. It is much longer on the first pair of legs than 

 on the second or third. The trochanter is very short. The femur 

 and tibia are both long joints, clothed with hairs and bristles. Most 

 important taxonomically among the latter are the apical and preapical 

 bristles of the tibiae, situated in the positions indicated by their names. 

 The five tarsal joints are all short, the basal one being the longest. 

 At the apex of the distal tarsal joint is situated a pair of minute curved 

 black claws. Beneath each claw is a minute white pad-like pulvillus. 



WINGS. 



The veins and cells of the wing of Drosophila melanogaster are shown 

 in figure 8, and need not be described in detail. 



^ Costa, or marginal vem 



Fig. 8. — Wing of Drosophila melanogaster. The parts are named on the diagram itself. 



Two costal breaks are to be seen; the proximal, just beyond the 

 humeral cross-vein, and the distal, just before the apex of the first vein. 



