30 DRAGON FLIES VS. MOSQUITOES. 



decaying substances in stagnant water, is frequently met in 

 popular works, but there seems to be little that is conclu- 

 sive in these statements, and we have been unable by ob- 

 servation to add anything of value. That they do feed 

 on minute animals, such as Cyclops, Cypris, etc., we have 

 observed, and that they have destroyed young trout is 

 attested by Westwood ^'^ and others. 



The external breathing apparatus of the larval Culicid 

 consists of a straight tube branching at an obtuse angle 

 near the anal extremity (Plate II., Fig. 1); this comnui- 

 nicates internally with the tracheal system. To use this 

 breathing tube, the larva needs simply to float at the sur- 

 face, head downward and the orifice in contact witli tiie 

 air. After three or four transformations the pupal stage is 

 reached (Plate II., Fig. 2), and here a remarkable change 

 in the appearance takes place. The head, thorax, legs, 

 and wings all being folded in one mass, and the abdomi- 

 nal segments being left free for the purpose of navigation, 

 the pupa has a very top heavy and clumsy appearance, 

 although it is quite as active as the larva, but not capable 

 of feeding. 



Butler ^^ describes an interesting feature of this period 

 as follows : " The most astonishino; change of all is that 

 which takes place in the respiratory system ; the entrance 

 to this is now transferred to the opposite end of the body, 

 and appears as two small twisted horns projecting from 

 the gigantic head. * * * Therefore it turns a somer- 

 sault in the water, and henceforth goes about head upper- 

 most." (Plate II., Fig. 3.) This change takes place at 

 the surface of the water within two hours. 



Authorities vary in their statements of the time passed 

 in the pupal state, but our observations on C. damnosus, 



