482 THE MICROSCOPE. 



the animal it attacks. On their outer surface they are 

 fleshy and muscular, to fit them to be employed as pre- 

 hensile organs ; while on their inner, they are more soft 

 and delicate, but thickly covered with rows of very minute 

 stiff hairs, directed a little backwards, and arranged closely 

 together. There are very many rows of these hairs on 

 each of the lips; and from thoir being arranged in a 

 similar direction, they are easily employed by the insect 

 in scraping or tearing delicate surfaces. It is by means of 

 this curious structure that the busy House-fly often occa- 

 sions much mischief to the covers of our books, by scrap- 

 ing off the white of egg and sugar varnish used to give 

 them the polish, leaving traces of its depredations in the 

 soiled and spotted appearance which it occasions on them. 

 It is by means of these also that it teases us in the heat 

 of summer, when it alights on the hand or face, to sip the 

 perspiration as it exudes from and is condensed upon the 

 skin. The fluid ascends the proboscis, partly by a sucking 

 action, assisted by the muscles of the lips themselves, 

 which are of a spiral form, arranged around a highly 

 elastic, tendinous, and ligamentous structure, with other 

 retractile additions for rapidity and facility of motion." 1 



The beautiful form of the spiral is best seen under a 

 magnifying power of 250 diameters, or a quarter-inch 

 object-glass. 



These insects are of great service in the economy of 

 nature, their province being the consumption of decaying 

 animal matter, which is found about in quantities so 

 small as to be imperceptible to most people, and is not 

 removable by ordinary means, even in the best-kept apart- 

 ments, during hot weather. It was asserted by Linnaeus, 

 that three flies would consume a dead horse as quickly 

 as a lion. This was, of course, said with reference to 

 the offspring of such three flies; and it is possible the 

 assertion may be correct, since the young begin to eat 

 as soon as they are born. A single Blow-fly has been 

 known to produce twenty thousand living Maggots ; and 

 each of these continues to eat so voraciously, that in 

 twenty-four hours it has increased its own weight above 

 two hundred times; in five days it attains to its full 



(1) Mr. G. Newport, Cyclopcedia, of Anatomy and Physiology. 



