18 BULLETIN 597, U. S. DEPARTMENT OF AGRICULTURE. 



developed and concealed within the rectum, but larvae less than 

 normal size, which were not exposed at the margin of the anus, did 

 not produce adults. Only larvae possessing the greenish color indi- 

 cating exposure at the margin of the anus were used in experiments 

 recorded in the tables. 



In Table II, of 347 larvae collected, 319 pupated and produced 236 

 adults, the pupa, period varying from 21 to 68 days. The greater 

 portion emerged during the shorter periods indicated in the table. 



FATE OF LARVAE DROPPING UNDER VARYING CONDITIONS. 



The variety of conditions under which larvae are dropped naturally 

 suggests the question of their ultimate fate. In an effort to deter- 

 mine this point by experiments, the most striking phenomenon ob- 

 served was the larval " migration " which precedes pupation.. In ex- 

 periments recorded in Table III, larvae placed upon the surface of 

 the soil or media penetrated to a slight depth for protection of the 

 pupae. With larvae buried in loose soil, as would ordinarily occur 

 when they are dropped by plow horses, they moved upward to near 

 the surface for pupation. 



