196 Papers from the Department of Marine Biology. 



Marquesas group. These keys are at the same time the largest and 

 the nearest to Rebecca Shoal— 24 miles east — and are largely covered 

 with mangrove swamps which furnish breeding-places for myriads of 

 mosquitoes. Their relation to the occurrence of these insects at the 

 light-station will be considered later. In succession, passing eastward, 

 lie Boca Grande, 6 miles distant from Marquesas; Man Key, Woman 

 Key, Crawfish Key; then Mullet, Barracouta, Cottrell, and Snipe Keys 

 at the entrance of Key West Harbor. It thus appears that any insect 

 which reaches Rebecca light-station by flight alone must cover either 

 12 miles from Tortugas on the west or 24 miles from Marquesas on the 

 east, or at least 105 miles from the mainland on the east and north, or 

 90 miles or more from Cuba. 



The station consists of a wooden dwelling 25 feet square and 26 feet 

 high, supported 34 feet above mean water-level upon an iron frame 

 understructure. A 10-foot platform surrounds the base of the dwelling 

 on all sides. The first story contains a single room 6 feet in height, 

 which is occupied by four large wooden tanks for the storing of rain- 

 water, and by a paint-closet and work-bench. The keeper's room, a 

 kitchen, and pantry open into a small hall on the second floor. From 

 here a stairway leads to the third floor, which is di^dded into a lamp and 

 oil room, two assistants' rooms, and a hall. A ladder gives access to 

 the lantern, Ught, and its mechanism at the top of the station. The 

 lantern is surrounded by a narrow balcony. The diagonals of the 

 station run north and south and east and west. At a level 8 feet above 

 the water are two small boat-landings, one each on the southeast and 

 northwest sides. 



MEANS BY WHICH INSECTS MAY REACH THE STATION. 



There are four conceivable ways in which insects may reach Rebecca 

 Shoal light-station. First by boat, for many are brought in provisions 

 and other stores. Several species of larder pests, including two weevils 

 and a flour beetle, two species of moths, one in flour and another in 

 raisins, and an occasional fruit-fly, were observed on the station. The 

 light-house power-boats usually bring on each trip a few house-flies and 

 occasionally a blow-fly. In one instance a Tabanus was introduced. 



It is extremely improbable that insects are attracted to the station 

 from vessels which must pass through Rebecca Channel at a distance 

 of at least 0.5 mile. Indeed none of the half dozen house-flies left the 

 yacht Antoji Dohrn on her voyage from Tortugas to Kej^ West on July 

 30, although she passed within 100 yards of the Rebecca station. It 

 is inconceivable that flies or mosquitoes voluntarily leave the soUd 

 support of a vessel where food is close at hand and its odors strong in 

 order to land on a small hght-station at a considerable distance. Any- 

 one who has been on board ship at sea has probably observed how 

 closely flies, beetles, dragon-flies, and moths keep to the vessel. 



