ii6 



note to his paper (1892) Emery states that the types of fulvescens 

 were found by Beccari in the hollow twigs of Cordia gerascanthos 

 in Guatemala, but I believe that this must be a very exceptional 

 occurrence,. as fulvescens is certainly the most abundant and most 

 typical acacia ant on both the east and west coasts of Guatemala 

 ^nd was taken by me on no other plants. It occurs in two varie- 

 ties, a larger and a smaller, the former running about with its 

 gaster directed backward in line with the thorax, the latter with 

 the gaster bent forward under the thorax after the manner of 

 Ps. kiinckeli Emery. 



Belt mentions only Ps. gracilis ( = bicolor) as occurring in 

 the thorns at Matagalpa, Nicaragua, and as this ant is ver}^ com- 

 mon in the hollow twigs of the most various trees and shrubs 

 throughout tropical America, Emery was incHned to believe 

 that Belt's specimens must have been incorrectly identified by 

 Fred. Smith. But such a supposition proves to be baseless, 

 since at Quirigua I found a region in the banana plantations 

 wnefc Ps. gracilis is the only ant occurring in the acacia thorns. 

 It thus appears that the obligatory ant fauna of the acacias diners 

 in difíerent parts of Central America, although it comprises, so 

 far as known, only four forms : Ps. belli and its subspecies ful- 

 vescens, Ps. spifiicola and nigrocincta. These differences are 

 produced merely by a great local predominance of one or two 

 of the species over the others. 



The facultative Pseudomyrmas comprise, so far as known : 

 Ps. gracilis, mentioned above ; Ps. subtillissima, a single colony of 

 which was taken by Alfaro in a tree occupied by Ps. belli ; and 

 Ps. nigropilosa Emery, of which Dr. Calvert sent me a few 

 specimens taken in acacia thorns at Santa Cruz, Costa Rica. 

 We must also assign three other ants of different genera to this 

 group of facultative species ; namely the Crematogaster men- 

 tioned by Belt as living in the thorns of some of the trees in 

 Nicaragua, Camponotus planatus Roger, also nesting in the 

 thorns, and a minute yellow Solenopsis sp., which I found nesting 

 in the flower peduncles. To the Solenopsis and Camponotus 

 I shall return after discussing the relations of the obligatory 

 Pseudomyrmas to the acacias. 



In Guatemala I found no ants on the dead acacias, which are 

 always abandoned by the obhgatory Pseudomyrmas, but Alfaro 



