THE DIPTERA OR FLIES 41 



piercing organs. All flies also pass through a complete 

 metamorphosis with sharply differentiated stages. If 

 familiarity always implied accurate knowledge it would be 

 unnecessary to say anything concerning the common house 

 fly (Musca domestica), but even entomologists have 

 learned much that was new regarding this insect within 

 the past few years. One of the most striking features 

 of the fly's organization is the proboscis which has long 

 been a favorite object with the amateur microscopist. 

 Most of this structure consists of the labium or lower lip. 

 Its end is flattened and divided into two lobes which 

 can be folded together when not in use or spread apart 

 and applied to a surface when the fly is sucking in food. 

 The lower surface of the lobes is roughened so as to serve 

 as a rasp or grater. 



The antennae of the fly are short and consist of three 

 joints of which the last is much the largest. Examination 

 of this joint with a microscope will reveal thousands of 

 olfactory pits, the organs concerned with the sense of 

 smell. This sense is very acute in flies, especially the blow 

 flies and flesh flies. The foot of the fly, another favorite 

 object of microscopists, shows in addition to two claws, 

 a two-lobed flap which is furnished below with minute 

 hairs at the end of which a sticky secretion is poured out, 

 that enables the fly to walk up vertical surfaces and upon 

 the ceiling. 



House flies produce many broods a year. Their eggs 

 are laid in horse manure and other refuse where they hatch 

 in less than a day into white maggots. In about six days, 

 the precise time depending upon temperature and food, 

 the larvae pass into the pupa stage, from which the mature 

 insect emerges in about five days. Besides making them- 

 selves an inordinate nuisance in the house where it is 

 apparently the height of their ambition to die in some arti- 



