DEPARTMENT OF MARINE BIOLOGY. 167 



In conclusion, it is a great pleasure to express our appreciation of 

 the fidelity and enthusiastic interest in their work exhibited by the crew 

 of the Anton Dohrn, and especially of Mr. John W. Mills, chief engineer, 

 to whose activity, interest, and intelligence we owe much of the suc- 

 cess of our trip to Samoa. 



REPORTS OF INVESTIGATORS. 



Report on Insect Investigation, by S. C. Ball, Massachusetts Agricultural College, 



Amherst, Massachusetts. 



In order to determine whether mosquitoes migrate from the mainland and 

 from Cuba across the sea to the Tortugas and neighboring points on the Flor- 

 ida reef, I spent the period from June 26 to July 18 upon the Rebecca Shoal 

 light-station. Observations were carried out there to avoid the uncertainty 

 arising at Tortugas on account of the breeding of mosquitoes upon the islands. 



The light-house is isolated in 12 feet of water, 12 nautical miles east of the 

 easternmost of the Tortugas keys, the nearest land ; 24 miles of open sea sepa- 

 rate Rebecca Shoal from the Marquesas Atoll on the east. The nearest point 

 on the mainland of Florida is Cape Sable, 105 miles to the northeast. Tampa 

 Bay lies very nearly due north at a distance of approximately 185 miles. The 

 nearest point on the Cuban coast is Havana, 95 miles south, while the distance 

 from Rebecca Shoal to Cape San Antonio, at the western extremity of Cuba, 

 is about 230 miles. 



The breeding conditions at the lighthouse were easily controlled. The 

 fresh-water reservoirs were examined daily, no larvae or eggs being found in 

 them at any time. Two other sorts of receptacles which at times contained 

 water were the small boats suspended from the davits and several depressions 

 in the iron work of the substructure. The water in the boats, besides being 

 easily examined, was covered with a film of lubricating oil from the gasoline 

 engines, while extremely rapid evaporation prevented any eggs deposited in 

 the small pockets of the iron-work from producing a brood of mosquitoes. 



Since none bred at Rebecca Shoal during the period of observations, those 

 which appeared could be accounted for only by their having been carried there 

 by vessels, by birds, or on their own wings, with or without the aid of wind, or 

 else by their having been on the structure at the time of my arrival. Now, the 

 station is small, 24 feet square by 26 feet high, and kept scrupulously clean 

 and free from litter. Hence it was easy to make a thorough search at the 

 beginning. Not a mosquito at any stage of its existence was heard or seen for 

 several days, good evidence that none were present. No vessels of any descrip- 

 tion passed within 2 miles of the lighthouse, except two small launches, which 

 were carefully examined. That birds could be responsible for the introduction 

 of other than parasitic insects is, of course, absurd. 



We are therefore to conclude that any mosquitoes encountered must have 

 flown or have been carried across the sea. Indeed, it will appear from the 

 table of weather conditions and the arrival of mosquitoes that this is the only 

 logical conclusion; only during and immediately following winds blowing 

 steadily for several hours from the direction of the nearer land areas — Florida, 

 Cuba, and Marquesas — ^were mosquitoes and other flies taken. 



It may be stated that, with the exception of a single mosquito which escaped 

 in an attempt to make its capture during a high wind, all mosquitoes and 

 house-flies seen were captured and preserved. 



