126 ESSENTIALS OF ZOOLOGY 



it easy to distinguish the larvae of anopheline and culicine 

 mosquitoes. The anal opening is terminal and surrounded by 

 four papillae. 



On account of the absence of a siphon the larva lies imme- 

 diately underneath and parallel to the surface of the water. 

 In this position it feeds greedily and changes its position by 

 backward jerking movements, and when disturbed it sinks to 

 the bottom. 



During its growth the larva sheds its cuticle several times, 

 and when fully grown it changes at once into the comma- 

 shaped nymph or pupa. In this state it does not eat, but 

 nevertheless it is capable of movement under certain condi- 

 tions. The pupa breathes by short funnel-shaped spiracles 

 situated dorsally on the thorax. This is also the case in the 

 culicines, but in them the spiracles are produced into long 

 slender tubes. After several days of nymph life the imago, 

 or adult insect, is produced from the pupa by exuviation and 

 begins its aerial life. It is very different from the preceding 

 stages. The body is elongated, the legs attenuated, the 

 thorax bears the membranous fore-wings and the rudimentary 

 hind-wings, called halteres. 



The head bears antennae, highly setate in the male, and 

 large eyes. The mouth appendages, which reach their highest 

 development in the female, consist of piercing and suctorial 

 organs and a sheathing organ. The former are designated 

 labrum-epipharynx, mandibles, maxillae (first pair with 

 their palps), and the hypopharynx. The sheathing organ is 

 the labium (the fused second pair of maxillae). In attacking 

 the host for the meal of blood the piercing organs inflict the 

 wound, the hypopharynx carries a stream of saliva into the 

 lesion, and the blood is drawn up the tube formed by the 

 apposed labrum-epipharynx and the hypopharynx. The 

 current of blood is induced by the pumping pharynx, which 

 is the anterior portion of the alimentary canal. The labium, 

 except to guide the stabbefs by its tip, takes no part in the 

 process, its chief function being to sheath the stylets when 

 at rest. The male, which is a vegetarian feeder, lacks 

 mandibles, while the maxillae are not so strongly developed 

 and the hypopharynx fuses with the labium. 



