COMMON FLIES AND HOW TO TELL THEM APART 141 



6. Deep, shiny blue fly often with a blackish tinge (about five-six- 

 teenths of an inch in length). Mouth-pai'ts of the suctorial type 

 (fig. 10a). The black blow fly (plate I, fig. 4). 



Phormia regina ISIeigen. 



III. Ashen gray to deep gray flies. Top of thorax with three blackish, 

 longitudinal stripes. The abdomen has lighter gray reflecting 

 spots (in certain lights). The diff'erent species vary in size 

 from a small fly up to a half inch in length. Mouth-parts are 

 of the suctorial type (fig. 10a). Flesh flies (plate III, fig. 1). 



Sarcophagidae. 



THE LARVAE OR MAGGOTS 



There is a considerable number of flies whose larva? or maggots 

 either regularly or occasionally live in substances used by man as food. 

 The great majority pass through the intestinal tract Avithout our 

 knowledge, for most of them cause little or no trouble. Many dipterous 

 larvcB occur in decaying fruits and vegetables and on fresh and cooljed 

 meats. The blow fly, for example, will deposit on meats in a pantry; 

 while other maggots occur in cheese, etc. Pies and puddings in restau- 

 rants are often accessible and very suitable places for flies to deposit 

 their eggs and no doubt a great many maggots are swallowed in this 

 way. The occurrence of dipterous larvae in man is known as "myiasis." 

 Various names or divisions are given, as "myiasis externa" or "myiasis 

 dermatosa" for larvae in the skin or wounds ; "myiasis intestinalis" for 

 those in the alimentary canal ; and "myiasis narium" for larva? in the 

 nose. The presence of larva? in the nose is rather accidental in this 

 country and usually due to the "screw-worm." In tropical countries this 

 type of myiasis is quite common. 



The larvae of the ox-warble or bot-fly {Hypodenna lineata Villers) 

 sometimes occur in man. There are various cases recorded, mostly of 

 children, where, in the Avinter time, a larva is observed under the skin, 

 usually in the neck or shoulders, and upon removal proves to be the 

 larva of the heel fly in the second stage. Bot infestation is sometimes 

 called "creeping worms," and many cases have been recorded by anny 

 surgeons on the Mexican border. These cases are probably contracted 

 by men sleeping in stable yards. 



Descriptions of larvae or maggots ^ 



All the larva; mentioned here are broadest near the tip or tail of the 

 body, and taper forward to the head. 



* In the following discussion the visible body segments are numbered from head 

 to anus irrespective of their scientific nomenclature. — W. D. Pierce. 



