ONION FLY. 



49 



short thick proboscis ; short horns of only three joints, 

 having a bristle at the tip ; and legs and wings of 

 moderate length. The maggots often taper to the 

 head, and are larger, and as it were cut short off, at 

 the tail, which is often furnished with tubercles, and 

 also with a pair of large spiracles, by means of which 

 the maggot can draw in as much air as it needs by 

 letting the tail project from whatever moist matter it 

 is lying in. The head is a soft mass, furnished with 



Fig. 43. — Onion Fly, maggot and pupa ; magnified. 

 Onion. Lines showing nat. size. 



Pupa in stored 



hooks instead of jaws, by means ofwhich the creature 

 can draw, or reap, into itself the soft substances 

 whereon it feeds. The head can be so completely 

 ■withdrawn into the maggot as not to show externally. 

 (For details see Fig. 47, p. 57.) 



The formation of the pupa-case, or puparium, is a 

 most important matter practically. We know it as 

 the small brown oval case, about an eighth, or a 

 quarter, of an inch long, which we find by maggot- 

 eaten Onions, or Cabbage-roots, or sometimes in dead 

 animals. It is formed of the hardened skin of the 

 maggot. This draws up, and within it the fly forms. 



