248 SIR HUBERT BOYCE THE PREVALENCE, DISTRIBUTION AND 



for a longer period than two years lose their vitality and become com- 

 pletely desiccated. Surgeon Francis * has also shown that eggs " may 

 remain viable for six and one-half months when kept dry." It should be 

 noted, however, that in this instance the eggs were not artificially dried, as 

 was the case wdth those which were forwarded to Liverpool from Manaos, 

 but were allowed to remain attached to the sides of the jar in which they 

 were laid, above the level of the water, and " set aside in a wardrobe in a 

 room which had no fire in it all winter and the doors and windows were 

 open night and day.'* The temperature in which these eggs were kept is 

 omitted also in this case. At the end of the period stated above, eggs placed 

 in a temperature of 80° F. produced larvae in seventeen hours, and adults 

 nine days later. After taking a meal of blood the adults laid eggs which 

 proved fertile, producing about 100 larvae six days after the parent insects 

 had emerged from the pupae. The complete cycle in this case whs sliorter, 

 by about two days, than that obtained by Goeldi in a tropical climate and 

 apparently under normal conditions. 



Peryassii f has also succeeded in rearing larvae from eggs which had been 

 exposed to dry atmospheric conditions for a period of five months ; and 

 adds that " this was the maximum time they resisted, and after this they 

 did not hatch.^' 



Boyce brought specimens of larvae alive to Liverpool which were collected 

 in Puerto Barrios in Guatemala on October 26tb. They were kept in a 

 test-tube exposed to the great variations of temperature which occurred in 

 travelling from Guatemala to New Orleans, New Orleans via Washington 

 to New York, and then across the Atlantic to Liverpool. The journey 

 occupied 25 days J. 



IX. Distribution of the Stegomtia in Africa. 



Stegomyia fasciata, according to Otto & Neumann, has been long known 

 in Senegambia, Sierra Leone and the Slave Coast, and in other parts of the 

 West (voast of Africa. There can be no doubt that the species has been 

 present certainly through the 18th and 19th centuries, that is to say during 

 the period of recorded outbreaks of yellow fever. Whether it was originally 

 introduced into the West Coast, or whether, like other mosquitos, it is an 

 original native of the Coast, it is quite impossible to be certain, seeing that we 

 know so little of the early history of insect life. We do know, however, 

 that the Stegomyia could readily have been introduced by any ship, from the 

 16th to the 20th century, trading between yellow^ fever countries and West 



* Public Health & Mar. Hosp. Serv. Rep. no. 14, vol. xxii, 1907. 

 t ' Os Culicideos do Brazil/ p. 373, 1908. 



X Yellow Fever Prophylaxis in New Orleans, 1905, Memoir xix. Liverpool School of 

 Tropical Medicine. 



