218 MEDICAL ENTOMOLOGY 



then sent to England in a well-corked test tube. He gives the fol- 

 lowing data : 



September 9th to llth ... Eggs laid in Manaos. 



October 26th ... Eggs reached England. Placed in 



water at a temperature of 23 C 

 (73'4 F). 



October 27th ... Twelve larvae hatched during the 



previous night, and one after 

 12 hours' immersion. 



October 28th . . . Larvae began moulting. 



October 30th ... All larvae completed first moult. 



November 4th ... Larvae pupated. 



November 7th ... First imago, a male, hatched. It 



lived for six days. 



November 8th ... A male and female hatched. 



In this experiment the eggs remained in a dormant condition for 

 about forty-seven days. The incubation period after they were im- 

 mersed in water lasted about twelve hours. The larval stage was com- 

 pleted in nine days, and the pupal stage lasted three days. 



Francis has shown that the eggs of S. fasciata may remain viable 

 as long as six and a halflmonths when they are kept dry ; they will not, 

 however, hatch after two years. Peryassu found that after five months 

 the eggs would not hatch. All these facts are of the utmost import- 

 ance in connection with the spread of Yellow Fever. 



The larva of this mosquito, like that of most of the genus, has a 

 long body, and a not very well-defined thorax. The syphon tube is 

 short and broad, and about one-quarter the length of the abdomen. 

 The antenna has a single spine of medium length on the inner aspect, 

 and a few small terminal hairs. The labial plate is described as 

 having eleven lateral teeth, and a larger central one ; its lower border 

 is crenulated. The lateral combs on the eighth segment have about 

 ten serrated spines. The spines on the syphon vary in number, and 

 are not a reliable guide ; they are, however, usually about eleven or 

 twelve in number. The larvae have the power of remaining for long 

 periods well below the surface of water. They are to be found in 

 collections of water in buckets, pails, old tins, broken bottles, etc., 

 in the vicinity of houses. They are commonly infected with a species 

 of Herpetomonas and a spirochaete, both of which are found in the 

 Malpighian tubes. 



Stegomyia sugens, Wied. Thorax dark brown, marked with four. 



