MOSQUITOES AND FILARIA 449 



segment. The thorax and legs are plain brown except for a pale 

 area at the bases of the legs. 



This species is very common in houses in all thickly populated 

 parts of tropical and subtropical portions of the world, though 

 not so thoroughly " domestic " as Aedes calopus. In America 

 it becomes abundant in summer as far north as Washington and 

 St. Louis. It is strictly nocturnal and will bite in complete 

 darkness, therefore its work supplements that of the yellow fever 

 mosquito, the latter taking the day shift, the former the night 

 shift. The house mosquito does not pursue man with as much 

 devilish cunning and perseverance as does Aedes calopus, and, 

 indeed, shows a very inferior grade of intelligence as compared 

 with it. There is reason to believe that it is primarily a perse- 

 cutor of birds and poultry, and attacks man only as a second 

 choice. C. quinquefasciatus breeds in almost any standing water 

 but apparently prefers artificial receptacles and is partial to filthy 

 water. The eggs, about 200 to 300 in number, are laid in rafts 

 as is the case with other members of the genus. The larvae 

 (Fig. 196 A), which hatch in from one to three days, have long 

 breathing tubes, and feed chiefly on microscopic organisms. 

 The length of time required for the mosquitoes to reach the adult 

 stage from the time the eggs are laid depends very largely on 

 temperature, food conditions, etc. The minimum period is 

 probably about five or six days. 



Alcock remarks about this mosquito: " Apart from its prac- 

 tical importance, Culex fatigans (or Culex quinquefasciatus) has 

 a peculiar interest as being the living document of two discoveries 

 of the first magnitude in the history of medicine, namely, Sir 

 Patrick Hanson's discovery ... of the part played by mos- 

 quitoes in the life cycle of certain filarial blood-parasites, and 

 Sir Ronald Ross's discovery ... of the necessary connection 

 between mosquitoes and certain Protozoon blood-parasites. The 

 first discovery laid open a new world to Pathology; the second, 

 which is the outcome of the first, will affect the destiny of the 

 human race." 



Mosquitoes and Filaria 



As intimated in the last paragraph above, the discovery by 

 Sir Patrick Manson in 1879 of the function of the mosquito as 

 an intermediate host of filarial worms, the larvae of which live 



