Ecological and Experimental Study of Sarcophagidce 53 



The pupal period is (]uite regular as far as observed; the dura- 

 tion of this stage varies, however, with the species. 



The emergence of the imagines from their pupal cases is inter- 

 esting. With the great blister-like frontal sac, not unlike a tiny 

 balloon attached to their heads, the case is burst and gradually 

 the body is withdrawn, much as a person might extric^^te himself 

 from a closely fitting tube. All the while the srnd particles are 



Fig. I Cut showing the manner in which screw-worm flies cHng to the beach grasses (Ammophila 

 and Panicum) after emerging from the pupa cases. Notice that the heads are mostly directed downward. 



thrown aside by the rhythmically inflated sac. Slowly, pull after 

 pull, the imago passes upward through the sand, and emerges at 

 the surface. After a moment of rest, it starts for the nearest grass 

 stem; up this it crawls in apparent haste, and there it remains to 

 unfold its wings. 



The accompanying plate shows the manner in which the 

 screw-worm fly clings to the stems and blades of the beach grasses 



