THE GEOGRAPHICAL DlSTRIBl'TIOX OP ANTS. 155 



subtropical countries it is able to propagate very rapidly and to exter- 

 minate the indigenous ant-fauna. This seems to be the case in Ber- 

 muda, and I have recently seen a good illustration of its habits in the 

 Virgin Islands. During March, 1906, I devoted ten days to a careful 

 study of the ant-fauna of the little island of Culebra, off the eastern 

 coast of Porto Rico, without seeing a single specimen of Ph. niega- 

 ccflia/a. This island is, however, completely overrun with a dark 

 variety of the vicious fire-ant (Solenopsis gcminata). One day, on 

 visiting the island of Culebrita, which is separated by a shallow channel 

 hardly a mile in width from the eastern coast of Culebra, I was aston- 

 ished to find it completely overrun with Ph. incgacephala. This ant was 

 nesting under every stone and log, from the shifting sand of the sea- 

 beach to the walls of the light-house on the highest point of the island. 

 The most careful search failed to reveal the presence of any other 

 species, though the flora and physical conditions are the same as those 

 of Culebra. It is highly probable that Ph. incgacephala, perhaps acci- 

 dentally introduced from St. Thomas, a few miles to the east, had 

 exterminated all the other ants which must previously have inhabited 

 Culebrita. The absence of megacephala on Culebra is perhaps to be 

 explained by the presence of the equally prolific and pugnacious fire-ant. 

 The recent displacement of Ph. mcgaccphala in Madeira and of our 

 native ants in Louisiana by Iridoinynnc.r huinilis is analogous to the 



FIG. 87. Worker of Plagiolepis longipcs, now spread over the tropics of both hemi- 

 spheres. (Bingham.) 



well-known displacement in Europe and America of the black house- 

 rat (Mits rattns) by the brown species (.!/. decnnianns) . In a similar 

 manner, according to Stoll, another ant, Plagiolepis longipes (Fig. 87), 

 introduced into the island Reunion from its original home in Cochin 

 China, has driven out some of the primitive autochthonous species. \Ye 

 may also look forward to the appearance of this same ant within the 

 warmer portions of the United States, since it has already been recorded 

 by Pergande (1894) from Todos Santos, in Lower California. 



