Transport hij Air 47 



the wind, as has been shown to be true for the monareh butterfly 

 (Wilhams et al., 1942). Consequently, regular transport by the 

 medium generally plays a far smaller part in the lives of land animals 

 than in the lives of the denizens of the sea. 



Occasionally the geographical range of an insect pest is extended 

 by wind action. A classical example of such an occurrence is pre- 

 sented by the spread of the gypsy moth in New England. This 

 foreign insect escaped from cages in which experiments were being 

 conducted in the vicinity of Medfield, Mass., in 1869. Since the 

 female of the species is flightless, one might suppose that the insect 

 would be confined to the immediate neighborhood of its point of 

 introduction, or at least would spread very slowly. However, the 

 species has a special way of "thumbing a ride" on the wind. The 

 newly hatched caterpillars in their first instar are provided with espe- 

 cially long hairs. When they crawl to the tops of trees and spin 

 long threads, they are soon blown ofl^ and are carried considerable 

 distances before they reach the ground. The caterpillars climb again 

 to the tree tops and the process is repeated. By this means, to the 

 detriment of the oak forests, the gypsy moth was spread throughout 

 New England within a few years. It even succeeded in crossing Cape 

 Cod Bay, a distance of about 40 km. 



The lifting power of the wind during hurricanes and tornadoes is 

 well known and provides an exceptional opportunity for the transport 

 of larger animals and plants in unexpected directions. Although in 

 most regions hurricane winds are rare, over the centuries they may 

 nevertheless have made possible the introduction of new species to 

 islands and other locations which would ordinarily be inaccessible to 

 the forms concerned. If the new arrivals become established and if 

 they are predatory or infectious or if they compete successfully, though 

 passively, with the native species, they may completely upset the eco- 

 logical adjustments of the existing community. 



It has long been recognized that the fauna of the Greater Antilles in 

 the West Indies has been derived in the evolutionary sense principally 

 from the Central American fauna. No convincing evidence has been 

 brought forward, however, that land bridges ever connected these 

 islands with the mainland of Central America. How the amphibians, 

 rodents, snakes, and other species of this general size ever reached the 

 islands remained a mystery until Darlington (1938) pointed out the 

 possibility of transport by the hurricanes which so frequently cross 

 this area. 



The exceptional lifting power of certain atmospheric disturbances 

 is illustrated by the "rain of fishes" which occurred in 1947 at Marks- 



