93 



and obligatory slave-makers, down to the degenerate permanent 

 parasites. 



Theories were discussed and criticised, new ones put forward, 

 and throughout the paper facts were illustrated by the most 

 striking observations and experiments of other myrmecologists 

 and numerous original ones of the authors (cf. Vol. II., p. ii). 



Discussion. 



W. M. Wheeler asked how males were treated, in replv to 

 which Mr. Crawley stated that as onh' three males of Ancr gates 

 were obtained, the first taken in Britain, it was considered advis- 

 able to preserve them and not to risk them by experiments. 



Dr. Sharp suggested that the refusal of queens was probably 

 a matter of taste. 



W. M. Wheeler then gave his paper entitled : 

 Observations on the Central American Acacia Ants. 



Early theories of symbiotic relations of ants and plants. 

 Treub and Rettig's researches, showing the independent origin 

 and function of the cavities in epiphytic Rubiaceœ. The species 

 of Acacia and their distribution. Division of Acacia ants into 

 " obligatory " and " facultative." The habits of the obligatory 

 Pseudomyrmas. The ants after removing the contents of the 

 thorns take up their dwelling in the hollow so formed. Un- 

 .attacked thorns also dry up and become hollow. If the tree be 

 disturbed, the ants emerge and attack the intruder. The found- 

 ing of colonies of ants in the young Acacia trees. Probable 

 coalition of many broods. Different species found associated. 

 Other insects, and sometimes birds' nests found in the Acacia 

 plants. Central American and African Acacia ants. Leaf- 

 cutting ants not sufficiently formidable to support symbiotic 

 theory of Acacia ants. The Acacia trees suificiently protected 

 by their thorns. Less defended species of Acacia and Acacia- 

 like plants thrive without the presence of ants. Ants have 

 probably become adapted to the Acacias, and are parasitic and 

 not symbiotic. Ant-infested Cecropias furnish no better support 

 for symbiotic theory. Species of Tnpiaris,'d large vigorous tree, 

 unlikely to tempt leaf-cutters, also inhabited by ants which live 

 in the cavities of the branches (cf. Vol. n., p. 109). 



