THE STUDY OP FRESH-WATER ANIMALS. 



185 



disturbed, swimming off quickly by the lashing of its flipper- 

 like tail (Fig. 72). On this pupa may be seen with a 

 lens the outline of several of the organs of the adult 

 insect. In about a fortnight or less the pupal stage is 

 completed. Soon after the gnats are seen to be entering 

 the pupal stage, a piece of muslin should be tied over the 

 mouth of the jar, and each morning the jar should be 

 examined for the adult insects, or for their emergence 

 from the pupa. 



This latter sight is interesting and should be watched. 

 The skin of the pupa splits at the back, and through the 

 opening the back of the 

 winged insect is pushed 

 up into the air. Next 

 the head, wings, legs, and 

 tail are withdrawn until 

 the insect stands at the 

 surface of the water upon 

 its former pupal husk. 

 Here it rests for some 

 time, until its wings are 

 stiffened and it has 

 gathered strength. Then 

 it flies away. About 

 the time the gnats are 

 hatching, if a cover has 

 been placed over the 

 vessel to prevent their 

 escape, numbers will be 

 found every morning resting upon the glass. 



The winged insect is equipped with a boring and sucking 

 apparatus for feeding purposes (Fig. 73). Male insects 

 suck the juices of plants, but the females attack animals 

 or men, sucking their blood. After a time these females 

 return to the water. They do not enter it, but resting on 

 grass or leaves at the edge of the pool they deposit their 

 minute eggs upon the surface where they float in a cluster. 

 The eggs in due time open on the under side, and from 

 them there pass out the larvae with which we started our 

 observations. The eggs, owing to their minute size, are 



Fig. 73. Adult female Gnat. Note tbe 

 blood-sucking proboscis in front. 



