CHAPTER VII. 



THE HOUSE FLY AND ITS ALLIES. 



THE common House fly, Musca domestica, scarcely needs an 

 introduction to any one of our readers, and its countenance is so 

 well known that we need not present a portrait here. But a 

 study of the proboscis of the fly reveals a wonderful adapta- 

 bility of the mouth-parts of this insect to their uses. We have 

 already noticed the most perfect con- 

 dition of these parts as seen in the 

 horse fly. In the proboscis of the 

 house fly the hard parts are obsolete, 

 and instead we have a fleshy tongue- 

 like organ (Fig. 84), bent up beneath 

 the head when at rest. The maxillse 

 are minute, their palpi (mp) being 

 single-jointed, and the mandibles (m) 

 are comparatively useless, being very 

 short and small, compared with the 

 lancet-like jaws of the mosquito or 

 horse fly. But the structure of the 

 tongue itself (labium, Z) is most curi- 

 ous. When the fly settles upon a 

 lump of sugar or other sweet object, it unbends its tongue, 

 extends it, and the broad knob-like end divides into two broad, 

 flat, muscular leaves (Z), which thus present a sucker-like sur- 

 face, with which the fly laps up liquid sweets. These two 

 leaves are supported upon a framework of tracheal tubes. In 

 the cut given above, Mr. Emerton has faithfully represented these 

 modified tracheae, which end in hairs projecting externally. 

 (80) 



84. Mouth-parts of the 

 House fly. 



