180 Psyche [December 



has kindly examined a pair and compared descriptions and re- 

 gards it as new. 



I am informed by Mr. Cameron of the Botanic Garden that these 

 insects were troublesome in the greenhouse for five or six years, 

 eating the tender green leaves of many kinds of plants and seem- 

 ing to be particularly fond of ferns; also, that they were believed 

 to have come originally from Jamaica. Their extermination is 

 believed to have been effected at least in part through the intro- 

 duction into the greenhouse of a number of small frogs. 



ANTS CARRIED IN A FLOATING LOG FROM THE BRA- 

 ZILIAN MAINLAND TO SAN SEBASTIAN ISLAND. 



By William Morton Wheeler, 

 Bussey Institution, Harvard University. 



Dr. Hermann von Ihering, the well-known writer on zoogeog- 

 raphy and till recently the director of the Museu Paulista of San 

 Paulo, Brazil, has sent me for identification some ants which were 

 taken under the peculiar circumstances described in the following 

 paragraph quoted from his letter : 



"I find that the 'raft-theory' of dispersal has generalized some 

 exact observations in an extraordinary manner. Here in South 

 America we have wonderful opportunities to observe the 'swim- 

 ming islands' in the great rivers, although the upper and lower 

 courses of these streams have to a considerable extent their own 

 peculiar faunas. My experiments with wood, bamboo, etc., con- 

 taining ant-colonies, have demonstrated that the latter are decided- 

 ly resistant to submersion provided their nest-entrances are closed. 

 Till the current year, one of our naturalists, Mr. Gaste, was, 

 however, unsuccessful in his various excursions in finding living 

 insects in wood that had drifted from our coast. One morning, 

 while he was on the island of San Sebastian, he found a tree 

 trunk that had floated to the shore during the night and was filled 

 with a living ant-colony belonging to a species of Pheidole un- 

 known to me. San Sebastian is situated some kilometers off the 

 coast of the main land. Of course, we cannot say how long this 



