254 TROPICAL MEDICINE AND HYGIENE 



the great variety of breeding-places, and of the wide 

 dissemination of this mosquito. 



In the first place eggs are often deposited in quite small 

 receptacles, shallow pools, gutters of houses, old tins used 

 for preserved foods, broken bottles, empty cocoanut shells, 

 &c., and it is immaterial if this deposition takes place at 

 the end of a spell of wet weather, as the eggs will remain 

 alive even if the water dries completely. With the next 

 rain, either there will be sufficient water to moisten the 

 eggs, or there will be an excessive amount, so that these 

 receptacles overflow. In the first case the eggs will hatch 

 where they were laid ; in the second, they will be washed 

 away into some larger and perhaps more permanent 

 collection of water. 



Eggs that have fallen to the bottom of a pond remain 

 alive, and if in taking water, as on board a ship, the 

 bottom is at all disturbed, the eggs will be taken with the 

 water, and hatch out and develop in the water-barrels. 

 Old wooden barrels in which water has been kept, if not 

 well cleansed, will often be found full of larvae within 

 twenty-four hours or less if refilled with water. Such 

 barrels are often used for storage of water on a small 

 scale and for catching roof water, and whether kept 

 indoors or out of doors are most prolific breeding-places. 

 With the onset of the wet season these species of 

 mosquitoes very rapidly become abundant. The mature 

 eggs are present in old beds of dried puddles, and in 

 every receptacle that will hold even a few drops of water, 

 and these hatch out with the first rain, and if rain con- 

 tinues the pupae will form in a week, and a day or two 

 later the imagines emerge. Light is not necessary for 

 the development of these larvae, so that cisterns and tanks 

 are suitable breeding grounds. 



The larvae have a respiratory syphon or tube attached 

 to the eighth abdominal segment. This syphon i s 

 present in all the Culicinae, but varies greatly in length. 

 In the Stegomyia it is a short, broad, stumpy syphon, 

 shorter than in most of the commoner Cnlicincc. The 



