ANATOMY. 



23 



hours. The final color is dark reddish-brown in Chymomyza procnemis, 

 Drosophila funebris, D. immigrans, D. repleta, D. virilis, and others, 

 paler and not reddish in D. melanogaster, D. obscura, D. simulans, and 

 others. The posterior spiracles and " pseudopodia " and the ventral 

 hooklets (also the dorsal processes of D. busckii) of the larva are 

 retained in the puparium. The anterior portion of the puparium is 

 flattened, and the pupa does not extend to the end in this region. The 

 cephalopharyngeal skeleton is left attached to the inner surface of the 

 larval skin. The tracheae coming from the anterior spiracles are broken 

 off, so that they do not connect with the pupa. This is apparently 

 true also of the tracheae leading from the posterior spiracles. 



The pupa itself is inclosed in a very delicate white 

 membrane, which is left behind when the adult 

 emerges. A few days after pupation the eyes be- 

 come pinkish, and gradually deepen in color, becom- 

 ing red as in the imago just before emergence. The 

 legs, wings, and bristles develop in characteristic 

 positions, that are occasionally retained in part after 

 emergence. Familiarity with these is valuable in 

 carrying out genetic experiments. A description of 

 them is accordingly presented. 



The condition of the wings at the time the adult 

 emerges is shown in figure 5, and needs no descrip- 

 tion. 



The front femora are twisted through 360° near 

 their bases. The other leg segments are straight. 

 The coxae all point posteriorly, the femora anteri- 

 orly, and the tibiae and tarsi again posteriorly. ■ The 

 legs thus lie closely and compactly against the ven- 

 tral surface of the developing imago. The twist in 

 the front femora is straightened at or before emerg- 

 ence, and is difficult to see, because it is apt to be 

 lost when an old pupa is dissected unless the operation be done very 

 carefully and examination made quickly. 



The bristles do not all point in the same directions as in the fully 

 expanded adult fly. The anterior orbitals point forward, the two 

 po.sterior ones backward and slightly outward, the tip of the longer 

 one lying over the eye. The postverticals and inner verticals point 

 inward, lying flat on the vertex. The outer verticals point outward, 

 Jfftrallel to the edge of the eye. The dorsocentrals point backward and 

 slightly inward, in such fashion as not to cross each other or the anterior 

 Sfjutellars. The humerals, presuturals, and anterior supra-alars point 

 E early straight backward. The anterior scutellars, postalars, posterior 

 supra-alars, and posterior notopleurals point backward and inward, 

 making an angle of about 45° with the dorsocentral lines. The 



Fig. 5.— Wing of 

 a newly emerged 

 Drosophila simu- 

 lans, that has not 

 yet unfolded. 



