108 DRAGON FLIES VS. MOSQUITOES. 



third seo-ments are about twice as broad as the remaining 

 ones; each segment along the sides is furnished with a 

 bunch of very short bristles. The anal segment is pro- 

 vided with a rather long tube, through which it breathes 

 by rising to the surface of the water. Its well known 

 rapid oscillating movement through the water is per- 

 formed by the quick lateral pulsations and lashes of its 

 tail, while it will often remain motionless for many mo- 

 ments at the surilice of the water, hanging head down- 

 ward from the liquid floor. Their food consists of minute 

 organisms and animal matters, and it has been suggested 

 that they free the stagnant swamps of miasmic regions of 

 their malarial and zymotic germs. 



The pupa stage lasts about four or five days. The 

 pupa is of a blackish color, with the wing cases and 

 thoracic segments enormously developed and the thorax 

 provided with two respiratory tubes. The abdominal 

 segments are considerably narrower than the thoracic ones, 

 and become slightly smaller towards the posterior end of 

 the body, which is furnished with two ofir like appendages 

 used for swimming. (Plate YIIL, Fig. 3.) Length 

 about three millimetres. After this stage succeeds the 

 emergence of the imago from its encasement. The deli- 

 cate shell of the pupa is ruptured by a short split near 

 the head, when the adult mosquito presses through the ori- 

 fice, and remains upon its fairy like boat, drying its wings 

 and gathering strength for its aerial or terrestrial life 



DISCUSSION OF THE PROBLEM. 



The actual injury inflicted by the mosquito can only be 

 approximately estimated ; the numerous instances, which 

 must escape all record, wherein the mosquito inflicts the 



