MOSQUITOES AND TRANSPORTATION 345 



" A few days later I visited the Kapapala Eanch, distant from Pahala about 

 four miles in an air line and about five miles from the ponds in question and 

 there found a similar state of affairs. Mr. Julian Monserratt, manager of the 

 ranch, told me that the invasion occurred at the same time as at Pahala prior to 

 which no mosquitoes had been seen at or near the ranch headquarters where, 

 indeed, there was no possible breeding place for them. 



" Unquestionably the clouds of mosquitoes originated in the same ponds below 

 Pahala and were carried by the trade winds not only to Kapapala but for miles 

 over the surrounding country in the direct track of the breezes. At Pahala, at 

 least, the colonization has proved to be permanent as here, as elsewhere on cane 

 plantations where water flumes are in use, leaky flumes form small pools at many 

 points along their track which make ideal breeding places for mosquitoes. . . . 



" Mr. Henshaw has since informed the writer that the ponds mentioned are 

 quite exposed and unsheltered by vegetation, and agrees with the writer that had 

 the ponds been surrounded by trees or had vegetation intervened to which the 

 insects could have clung for shelter, the distribution would not, probably, have 

 been so widespread." 



It is doubtful that the trade wind played the role in the dispersal of these 

 mosquitoes attributed to it by Mr. Henshaw. It should be noted that Culex 

 quinquefasciatus is nocturnal and it is well known that the trade wind dies down 

 at night. The mosquito's greatest activity therefore occurs at the time when the 

 air is calmest. It does not follow from Mr. Henshaw's account that he actually 

 saw the mosquitoes being carried by the wind; he found the mosquitoes and 

 concluded that the wind had brought them. This last criticism will also apply 

 to a very large part of the previously quoted observations. 



CARRIAGE OF MOSQUITOES BY SHIPS. RAILROADS. AND 



OTHER CONVEYANCES. 



Just as is the case with many insects now cosmopolitan and which have been 

 taken from their original home to other parts of the world through the opera- 

 tions of commerce, mosquitoes are carried not only from one part of a given 

 country to another in carriages, in railroad trains and on river boats, but they 

 have been, and are yet, to a more limited extent perhaps, carried from one 

 country to another by ocean vessels. It seems reasonably well established that 

 Hawaii had no aboriginal mosquito fauna and that the mosquitoes found there 

 were brought over in sailing vessels many years ago ; these could only have main- 

 tained themselves during a long voyage by breeding in the water supply of those 

 vessels. In this way it is a practical certainty that the yellow fever outbreak in 

 Philadelphia in 1793, and the other less grave epidemics in northern cities pre- 

 ceding and following that notable occurrence, were brought about by the arrival 

 in these ports, at the proper season of the year, of sailing vessels from the West 

 Indies carrying Aedes calopus. Perhaps these mosquitoes were already infected, 

 or breeding in the water supply of the vessels, biting yellow-fever patients on 

 board at the proper period, and afterward healthy individuals, would perpetuate 

 the disease. Such a vessel tying up to a wharf might emit many infected mos- 

 quitoes which, biting persons on land, and subsequently breeding in numbers in 

 water barrels or other accumulations of fresh water on or near the wharves. 



