2o8 
Arthropods as Hosts of Pathogenic Protozoa 
The life cycle under favorable conditions is completed in from 
twelve to fifteen days. These figures are of course very dependent 
upon the temperature. The Army Commission in Cuba found that 
the cycle might be completed in as brief a period as nine and a half 
days. Under less favorable conditions it may be greatly lengthened. 
The adults are long lived. We have 
seen that during the experimental work 
in Cuba specimens were kept in cap¬ 
tivity for sixty-nine and seventy-one 
days, respectively, and that they were 
proved to retain their infectivity for at 
least fifty-seven days. Dr. Guiteras 
subsequently kept an infected adult for 
one hundred and fifty-four days. 
Low temperatures have a very great 
effect not only on development, but on 
the activity and even life of the adults. 
Long before the method of transmission 
of yellow fever was discovered it was well 
known that the epidemics were brought 
to a close by heavy frosts, and it is now 
known that this is due to the killing of 
the mosquitoes which alone could spread 
the disease. 
Aedes calopus has a very wide distri¬ 
bution since, as Howard says, being a 
domestic mosquito, having a fairly long 
* life in the adult stage, and having the 
custom of hiding itself in the most ingen¬ 
ious ways, it is particularly subject to car¬ 
riage for long distances on board vessels, 
in railway trains, even packed in baggage. In general, its permanent 
distribution is from 40 degrees north latitude to 40 degrees south 
latitude (Brumpt), in a belt extending around the world. In the 
United States it breeds in most of our Southern States. 
Thus, as in the case of malaria, there are many places where the 
insect earner is abundant but where yellow fever does not occur. 
Such, for instance, are Hawaii, Australia and Asia. An outbreak may 
occur at any time that a patient suffering from the disease is allowed 
to enter and become a source of infection for the mosquitoes. In 
1356. Aedes calopus; larva. (x 7 ). 
After Howard. 
