384 



Chapter XXXII 



YELLOW FEVER 



The cause of the disease is unknown. The following 

 facts have been established : 



(1) Stegomyia calopus that has fed on a patient 

 during the first three days of the fever can transmit the 

 disease twelve days later, but not before. This period 

 is longer if the temperature of the air is low (e.g. 80 F.). 



(2) The incubation period in the patient is 

 two to six days. 



Stegomyia calopus. A black and white mosquito. 

 Proboscis unbanded. Thorax ornamented with a 

 curved silvery line on each side and two median 

 parallel lines, giving the characteristic lyre pattern. 

 Hind tarsi basally banded with white, the last tarsus 

 being all white (Plate VI). 



Habits. According to some observers this mos- 

 quito, after the first week of life, bites only at night 

 (5 p.m. to 7 a.m.), but this is doubtful, though probably 

 feeding generally takes place at night. 



Breeding Places. Breeds especially in ' domestic ' 

 collections of water in pots, pans, barrels, jars, tins, 

 cisterns, boats, troughs, etc., etc., but not commonly 

 in natural puddles. 



Egg-laying:- Occurs chiefly at night, sixty to 

 seventy being laid. They measure 550 by i6o//< (p. 67). 

 The eggs will hatch after being kept ' dry ' for some 

 months. Hibernation is probably mainly by the eggs. 



