115 



near San Lucas Toliman, Lake Atitlan 4,000 ft. (W. ^L Wheeler); 

 Rio de las Cañas, Punta Rosa, 2,000 ft. (HEYDEand Lux.), Gray 

 Herb. 



Mexico: Manzanilla Bay (Hinds), Bentham ; Manzanilla. 

 Colima (C. H. T. Townsexd), Amer. Mus. C(j11. ; La Orilla and 

 San Luis between Michoacan and Guerrero (Michèle), Gra^' 

 Herb. ; Jamiltepec to Rio Verde 400 to 1,000 ft. (E. W. Nelson), 

 Gray Herb. ; between Llano Grande and Pinotepa, 200 to 500 ft. 

 (E. \V. Nelson), Gra}- Herb. ; Escuinapa, Sinaloa (J. H. B.\TTY), 

 Amer. Mus. Coll. 



Acacia sphcBroccphala Schlechtendal and Chamisso. 



Panama : Las Sabanas (W . M. Wheeler). 



Mexico : Actopan, Vera Cruz (Schiede), Schlechtendal and 

 Chamisso ; Vera Cruz to Texas (Bentham) ; Yucatan (G. F. 

 Gaumer), Gray Herb. 



Obligatory and Facultative Acacia Ants. 



Just as there are certain species of the dendrophilous ant- 

 genus Azteca that live only in Cecropia trees, so there are certain 

 species of the ecjualh' dendrophilous genus Pseudomynna that 

 live exclusively on the three large-thorned acacias. These I 

 shall call " obligatory " acacia ants. Several other species of 

 the same genus, which are only occasionally associated with 

 these plants, may therefore be designated as " facultative." 

 To the former group belong the three species which Emery 

 determined, from specimens collected by Alfaro in Western 

 Costa Rica, as Ps. hclti Emer\', spinicola Emery, and nigrocincta 

 Emer\\ These species are all of about the same size, but differ 

 in colour, belli being black, spinicola red, and nigrocincta yellow, 

 with a black band across the base of the gaster. I may note in 

 passing that Dr. P. P. Calvert recently sent me specimens of 

 Ps. belli and nigrocincta, taken from acacia thorns in Santa Cruz, 

 Guanacaste, Costa Rica. I have taken spinicola only in Panama 

 on A. sphceroccphala. In Guatemala the only obligatory Pscudo- 

 viyrmce seen on A. conigcra and hiudsii are the t\'pical belli, and 

 a red subspecies of this ant. fidvcscens Enicrx . the former occur- 

 ring very rarely, tlu' hitttr en nearly all thr trco. In a foot- 



