THE YELLOW-FEVER MOSQUITO 107 



The pupa of Stegomyia is darker and 

 blacker than that of Culecc, and, seen from the 

 side, the head and the thorax are somewhat 

 more triangular than the same parts in Culex. 

 As the pupa grows older it grows darker. 

 The length of the larva is 4 to 6 mm., somewhat 

 larger than that of the 

 gnat. But, like that, it 

 has a respiratory-tube 

 stretching out from the 

 last segment of the abdo- 

 men, almost at right angles 

 to the rest of the body. 

 This respiratory-tube is 

 much shorter than that 

 of Culex, but is long enough 

 to enable the larva to 

 hang obliquely down into 

 the water. The eggs are 

 very large. They are covered by a mass 

 of small ' cells ' containing air, and they never 

 tend to form a conglomerate mass like those 

 of Culex, but are laid singly, and remain 

 isolated until the larvae hatch. After floating 

 a certain time they usually sink to the bottom 

 of the water. Their length may be about a 

 millimetre, and their colour is almost black. 

 When the egg hatches, the anterior third of 

 the shell splits off and the larva at once 

 emerges. 



Fig. 28. — Larva of Ste- 

 gomyia fasciata breathing 

 on the surface of the water. 

 Highly magnified. 



