150 THE COMMON HOUSE-FLY. 
church as well as the public speakers, during some of their 
most eloquent passages, must scratch their noses as freely as 
does the poor laborer who diligently or otherwise digs 
trenches for anew 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 
maxillz 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-fly. But the structure of the tongue it- 
self (labium), is most curious. 
45 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 sucker- 
like surface, with which the fly laps — 
up the liquid sweets. These two 
leaves are supported upon a frame- 
work of tracheal tubes; these modi- 
fied tracheze end in hairs project- 
Fig. 126.—Mouth-parts of ing externally. Thus the inside of 
house-fly. Greatly enlarged. : ‘ 3 
Original. this broad, fleshy expansion is 
rough like a rasp, and, as Newport states, “is easily 
employed by the insect in scraping or tearing delicate sur- 
faces.’’ It is by 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 much time to describe them 
now in detail. 

“The very fact that flies run over our skins in search of 
