Insects at Rebecca Shoal and Tortugas. 199 



and of the contents on June 27 failed to reveal a single trace of larvae, 

 pupa3, molted skins, or adults which might have been drowned in the 

 act of depositing eggs. Indeed, the lighthouse keepers, Mr. Lopez 

 and his assistants, all of whom were familiar with the larvae, agreed 

 that they had never noted in water drawn from the tanks a single 

 "wiggle-tail." Had larva? been present they would probably have been 

 detected, for the water is all drawn from the bottom of the reservoirs. 



Owing to the ease and thoroughness with which frequent examina- 

 tions of these tanks could be made, it was deemed unnecessary to treat 

 the water surfaces with kerosene. Vigilance and daily examinations 

 throughout the period of observations disclosed no sign of mosquitoes 

 at any stage of their life-history in the reservoirs. 



The third possible breeding-place (the boats), is also an extremely 

 unfavorable one. In the case of the power launch a heavy film of 

 lubricating oil is always present, while the sea-water in the bottom of 

 the small dory, besides being too saline owing to evaporation, is also 

 easily examined. No mosquitoes bred there. 



From the above statement of conditions and the past experience of 

 the keepers it is clear that mosquitoes rarely, if ever, breed at Rebecca 

 Shoal light-station. Certainly none attempted to do so during the 

 period covered by these investigations. 



CONDITIONS JUST PRIOR TO JUNE 26. 



In order to account properly for the presence of certain insects 

 found upon Rebecca shoal light-station on June 26 it is desirable to 

 acquaint the reader with the conditions obtaining there in the period 

 just preceding. From the lighthouse journal it was learned that on 

 June 13 the keepers began painting the station, working that day upon 

 the southeast side. At that time the wind was blowing freshly from 

 the northeast. In other words, the air-current passed swiftly across 

 the painted surface of the building ; it was not on the lee side. Follow- 

 ing several hours of calm on June 14 a light north wind sprang up and 

 continued until June 15, when it became somewhat westerly, finally 

 dying out, to be followed by 36 hours of calm. 



It is of interest to note than on June 15 a coat of white paint was 

 applied to the southwest side of the dwelling, and particularly that 100 

 or more small gnats were later found stuck in this paint. Now, it will 

 be seen that this southwest face of the building was, in the period 

 following the application of the paint, in the lee of the north and north- 

 west winds; therefore, the insects seeking a resting-place on this surface 

 were caught. Since they are not species that would have been brought 

 in stores, it seems a fair conclusion that they were carried by the nor- 

 therly wind from the coast of Florida. The possibility is not excluded 

 that these gnats were brought to the station on the northeast breeze 

 of June 13 and harbored there until the application of the paint. 



