Insects at Rebecca Shoal and Tortugas. 203 



ture of a specimen at this early hour, just as day was breaking. An- 

 other was taken at S^'SO™, and during the next 3 hours of the morning 

 mosquitoes were so numerous that at times 2 or more could be cap- 

 tured with one sweep of the net; at 8^15™ a. m. the count stood at 14 

 specimens. At intervals during the day others appeared, the last at 

 8 p. m., which made the total 21 for the day. 



Now this marked increase in the number of mosquitoes encountered 

 at the station, following a shift of 90° or more in the direction of the 

 wind, from east to north by west, gains more significance as we note 

 the interval of time elapsing between the inauguration of this change 

 and the appearance of the insects. As already stated, at least 27 

 hours had passed from the time when, on the night of July 2 and 3, the 

 wind was blowing from the vicinity of Cape Sable, 105 miles to the 

 northeast on the southwest point of Florida, and the arrival of the first 

 mosquito at Rebecca Shoal at 8 a. m. on July 4. That only 1 specimen 

 was taken at this time indicates that comparatively few mosquitoes 

 were blown out to sea from the southern capes. Not until toward 

 night, after the wind had been blowing for over 37 hours, did the num- 

 bers begin to rise. The inference is that as the wind shifted — assuming 

 that its direction held over the entire distance — points farther and farther 

 north on the west coast of Florida contributed to the forced migration 

 of mosquitoes. As will appear, the species taking part were only such 

 as breed in salt marshes ; therefore, those regions having such swamps 

 would send out large swarms. 



It will be seen that the body of the swarm encountered at Rebecca 

 Shoal arrived on July 5, after the wind had been blowing from due 

 north — the direction of Tampa Bay — for 48 hours or more. Obviously 

 it can not be determined just how far up the coast these mosquitoes 

 originated, but it is certainly possible that some of them may have 

 come from points 150 miles to the north. 



The specimens taken on this migration proved on determination to 

 belong to two species. A single one of Aedes sollicitans was captured 

 on July 4. The other three, as well as the 21 taken on July 5, were 

 of the species Aedes niger. A . sollicitans and A . tceniorhynchus (a species 

 closely allied to A . niger) have become noted for their migratory habits 

 through the researches of Dr. Smith, of New Jersey. Breeding in the 

 salt marshes along the seashore each summer develops immense swarms 

 which spread inland to harass the inhabitants of cities even 30 miles 

 away. In New Jersey A. sollicitans with A. cantator is the dominant 

 species, tceniorhynchus being much less important, according to Dr. 

 Smith: 



"Culex tmniorhynchus develops with cantator and sollicitans under the 

 same conditions and migrates with them; but it does not fly so far and is 

 always so much less abundant that it needs no special account here." 



In the south, however, A . niger appears to be the dominant species and 

 certainly flies, or is carried by winds, over the sea for long distances. 



