ii8 



Ps. nigrocincta Emery. 



Costa Rica : Alajuela and Jimenez (A. Alfaro) ; Santa Cruz, 

 Guanacaste (P. P. Calvert). 



Ps. nigropilosa Emery. 

 Costa Rica : Santa Cruz, Guanacaste (P. P. Calvert). 



Ps. gracilis Fabr. 

 Guatemala : Quirigua (W. M. Wheeler). 



Ps. suhtillissima Emery. 

 Costa Rica : Alajuela (A. Alfaro). 



Crematogastcr sp. 

 Nicaragua : Matagalpa (Belt) . 



Solenopsis SP. 

 Guatemala: Escuintla (W. M, Wheeler). 



Campanotus planatus Roger. 

 Guatemala : Costa Rica (A. Alfaro) ; Zacapa, Quirigua, 

 Escuintla, and Patulul (W. M. Wheeler). 



The Habits of the Obligatory Pseudomyrmas. 



As Belt observed, the stipular thorns of the acacias are at 

 first rather soft and green, and contain a watery, sweetish pulp. 

 Only after they reach their full size and shape do the ants pay 

 any attention to them. Then the insects select a spot near the 

 tip of one of the thorns of each pair, make an elliptical hole in 

 the cortex, and dig out the pulp. I am not sure that the ants 

 eat this pulp, as Belt impHes, but this is not improbable, con- 

 sidering its sweet taste and the large amount of water it contains. 

 After one thorn is hollowed out, the excavation is carried through 

 its base into the adjoining one, which is also reduced to a mere 

 shell. All the particles excavated from both thorns are carried 

 out through the single orifice, and one almost never sees a pair of 

 thorns with an opening near the tip of each. During or just 



