Ecological and Experimental Study of Sarcophagidce 55 



deposits living young. The average v\^eight of newly extruded 

 larvae, before any food has been taken, is about 0.2 mg-'^ The 

 growth of the larvae is very rapid, and the feeding period is 

 about the same as Lucilia caesar (two to two and a half days), 

 but pupation takes place more regularly. The interval between 

 migration and pupation is about three days, and the pupal period 

 covers about thirteen days. Thus the period of development for 

 this species is from eighteen to nineteen days. 



Compsomyia macellaria Fabr. : The screw-worm fly is very 

 abundant along the beach, far outnumbering Lucilia caesar. 

 Ordinarily living young are deposited. These can be distinguished 

 from Sarcophaga sarraceniae larvae by their small size and lack 

 of the prominent dark coloration of the head. The complete 

 larval period requires about five days, the pupal period about 

 four days, thus giving a very short period of development, namely, 

 about nine days. 



Sarcophaga assidua Walker: Of this species only two adults 

 were reared. This small gray flesh fly, strongly resembling the 

 house fly in size and appearance, has a larval period of five and 

 six days for the two reared, and a pupal period of seven days, 

 giving a total of from twelve to thirteen days for development. 



Ill NORMAL GROWTH OF FLIES THROUGH LARVAL AND PUPAL 



STAGES 



In taking up the study of growth of the species below named, it 

 was decided that weight is the most convenient and most readily 

 applied method of measurement for these forms. As weight has 

 been the basis of measurement for observations made by other 

 investigators, it also forms a readier means for comparison. 



Growth is best represented graphically by means of curves, and 

 below is thus shown the course of growth of Lucilia caesar and 

 Sarcophaga sarraceniae in terms of weight in milligrams. 



The eggs of Lucilia for this experiment were collected and 

 weighed on the afternoon of July 12, 1905. The larvae emerged 

 early July 13, when the larvae of Sarcophaga sarraceniae were 



^This weight was obtained by weighing two sets of ten on August 31, 1905, which gave a total 

 of 2 mg,; throwing the two sets together gave 4 mg, for the twenty larvae. 



