126 NATURAL HISTORY READER. 



which the perfect insect develops itself in the course oi 

 two or three days. While in the water the larva and pupa 

 are both familiarly known as wigglers. 



7. When about to undergo its last change, the pupa 

 lies extended on the surface of the water with its thorax a 

 little raised. In a moment the skin splits, beginning at 

 the head and extending along the back. As soon as it is 

 enlarged — and to do so sufficiently is but the work of a 

 moment — the forepart of the perfect insect is not long 

 in showing itself ; and soon afterward the head appears, 

 rising above the opening. But this moment, and those 

 that follow, until the mosquito has entirely left its cover- 

 ing, are most critical, and when it is exposed to great 

 danger. This insect, which lately lived in the water, is 

 suddenly in a position in which it has nothing to fear so 

 much as the water. If it were upset on the water, and the 

 water were to touch its thorax or body, it would be fatal. 



8. This is the way in which it acts in this critical po- 

 sition : As soon as it has got out its head and thorax, it 

 lifts them as high as it is able above the opening through 

 which they had emerged, and then draws the posterior 

 part of the body toward the same opening ; or, rather, 

 that part pushes itself forward by contracting a little, and 

 then lengthening again, the roughness of the covering from 

 which it desires to extricate itself serving as an assistance. 



9. A large portion of the mosquito is thus uncovered, 

 and at the same time the head is advanced farther to- 

 ward the anterior end of the covering ; but as it advances 

 in this direction it rises more and more, both ends of the 

 sheath thus becoming quite empty. The sheath is now 

 a kind of boat, into which the water does not enter ; and 

 it would be fatal if it did. Large boats, which pass under 

 bridges, have masts which can be lowered ; as soon as the 

 boat has passed the bridge, the mast is hoisted up by de- 

 grees until it is vertical. The mosquito rises until it be- 



