127 



cases may now be added the association of Ps. hclti with Ps. 

 suhtillissima, and of Ps. fulvescens and gracilis with C. planatus. 



Other Organisms Associated with the Acacias. 



It is probable that other insects besides the ants occasionahv 

 visit the extrafloral nectaries of the acacias. Belt states that 

 these organs are " frequented by a small wasp {Polybia occiden- 

 talis)." But besides the ants and the Coccids mentioned above 

 as living in the hollow flower peduncles of A. cornígera, I saw 

 only the following insects or evidences of their occurrence on the 

 plants : — 



1. In some localities (Escuintla, Patuhil) the upper surfaces 

 of the pinnae of C. cornígera bore beautiful little spherical galls, 

 5 to 6 mm. in diameter, singly or in clusters, and resembling 

 minute strawberries, as they were bright red and uniformly 

 covered with papillae. Each of these galls contains a Dipteran 

 (Cecidomyiid ?) larva and has a preformed rhaphe along which 

 it dehisces when brown and mature, and permits the adult fly 

 to escape. Ps. fulvescens is very fond of visiting these galls 

 when 3'oung and succulent, and was often seen gnawing away the 

 covering of papillae, but not eating in far enough to injure the 

 enclosed larva. 



2. A second gall of larger size and woody texture was occa- 

 sionally seen on the flower stems of A. hindsii, but as I saw only 

 old and dried specimens, I am unable to make any statement 

 in regard to the insect. 



3. The brilHant yellow flower spikes of A. cornigera are pol- 

 linated by small bees which resemble some of our northern 

 species of Halictus. 



4. On some of the acacia trees and bushes I found the i)aper 

 nests of various species of Polybia, some deserted, but others 

 still occupied by the wasps. 



5. Along a road near Escuintla I found several young acacias 

 wholly or in part defoliated, though tlu ir thorns were still teem- 

 ing with Ps. fulvescens. There were no leaf-cutters in the vicinit}', 

 and the defoliation was not of the type characteristic of these 

 ants, but resembled that of certain caterpillars or Chr}-somelid 

 beetle larvœ. 



