15() 



THE COMMON HOUSE-FLY. 



church as well as the public speakers, during some of their 

 most eloquent passages, must scratch their noses asfreeh^as 

 does the poor laborer who diligenth' or otherwise digs 

 trenches for a new gas company. A study of the proboscis 

 of the fly (fig. 126) reveals a wonderful adaptability for its 

 uses and misuses. In this proboscis, we see a fleshy, tongue- 

 like organ, bent up beneath the head when at rest. The 

 maxillge are minute, their palpi being single-jointed, and the 

 mandibles or jaws are comparatively useless, being very 

 short and small, compared with the lancet-like jaws of the 



mosquito or horse-fl3' 



But the structure of the tongue it- 

 self (labium), is most curious. 

 When a fly settles upon a lump 

 of sugar or other sweet object, it 

 unbends its tongue, extends it and 

 the broad knob-like end divided 

 into two broad, flat, muscular 

 leaves which thus present a siicker- 

 like surface, with which the flv laps 

 up the liquid sweets. These two 

 leaves are supported upon a frame- 

 work of tracheal tubes; these modi- 

 fied tracheae end in hairs project- 

 ing externalh'. Thus the inside of 

 this broad, fleshy expansion is 

 rough like a rasp, and, as Newport states, ''is easily 

 employed b_v the insect in scraping or tearing delicate sur- 

 faces." It is b^^ means of this curious structure that the 

 busy house-fly occasions such mischief to the covers of our 

 books by scraping off the albuminous polish and leaving 

 tracings of its depredations in the soiled and spotted ap- 

 pearance which it occasions on them. It is by the means of 

 these that it teases us in the heat of summer, when it alights 

 on the hand or face to sip the perspiration that exudes from 

 and is condensed upon the skin. The microscope reveals 

 wonders quite unexpected in such a common insect as the 

 house-fly, but it will take too miich time to describe them 

 now in detail. 



"The verv fact that flies run over our skins in search of 



FiR. 126.— Mouth-parts o 

 hovise-fly. Greatly enlarged 

 Original. 



