150 



SANITARY ENTOMOLOGY 



part of each ring is much broadened and divided transversely by a narrow 

 smooth space. On segments 5 to 10 there is on each side behind a fusi- 

 form swollen area pressing against the swollen ring of the next segment ; 

 this area also has spines. The tip of the body shows on the dorsal part 

 a great cavity, in the bottom of which are the stigmal plates, each with 

 three straight slits, those of one sub-parallel to those of the other ; 

 there is no button (fig. 30). Behind this cavity is a higli, transverse, 

 spiny crest ; and the ventral part of the tip shows an area covered with 

 spines bearing two rather widely separated, prominent, smooth tubercles. 

 The upper edge of the tip shows four small conical tubercles. 



Plate IV. — Screw worm injury to a yearling calf. (Biahopp.) 



The larva of this insect is called the "screw-worm," and occurs in 

 sores and wounds of domestic animals and also in man. There are 

 various records of its presence in the ears and nose, or nasal cavities, 

 of people ; in swellings near the nose ; in a boil under the arm ; under the 

 skin of a child ; and in the navel of a child. It is hardly a possible 

 factor in intestinal myiasis of man, and most of such recorded cases 

 probably belonged to some species of Sarcophaga whose larvje are very 

 similar in appearance to those of the screw-worm. 



Sarcophagidae 



The Sarcophagidae have two great hooks, and the posterior stigmal 

 plates have three slits as in Calliphora erythrocephala and Lucilia seri- 



