TURRUCARES AND RIO GRANDE DE TARCOLES 367 



behalf of their own bodies and their brood, and, therefore, 

 that we may adopt von Ihering's point of view, and say 

 that the Acacias have no more need of their ants than dogs 

 have of their fleas. "If this is true, the relation between the 

 ants and plants is not one of symbiosis, but of parasitism." 



About fifteen feet from the bank of the Siquiares there was 

 a fairly large nest of the leaf-cutting ants and at one edge of 

 the nest stood a bull's horn thorn with its Pseudomyrma 

 inhabitants. I knew that the leaf-cutters cut and carry off 

 pieces of the leaves of plants allied to this acacia. With 

 my forceps I gently picked up a leaf-cutting ant from the 

 ground and put it near the tip of a leaflet of the bull's horn 

 thorn. There were only one or two Pseudomryma on the 

 leaflet and they did not seem to pay much attention to the 

 leaf-cutter, which, after a little wandering, fell off to the 

 ground. I picked up another leaf-cutter and placed it upon 

 a pair of thorns where there were a number of the Pseudo- 

 myrma. Although the latter were much smaller than the 

 leaf-cutter, they instantly rushed at it and one seized hold 

 of one leg, one another leg. The leaf-cutter ran to and fro 

 with the result that it finally fell to the ground, but whether 

 pushed or thrown by the assailants or as a result of its own 

 efforts to escape, I could not tell. I repeated this experiment 

 several times, always with the same result except that once 

 when the leaf-cutter fell, the Pseudomyrma was still clinging 

 to one leg and the leaf-cutter dragged it around over the 

 ground for some distance before it released its hold. I also 

 put a Pseudomyrma among some leaf-cutters near an en- 

 trance to their nest, but no actual violence resulted. 



On August 13 Professor Tristan found a Peripatus similar 

 in appearance to those we obtained at Turrialba, and later 

 in our stay found two more. 



On the 13th, 14th and 15th we caught along the Siquiares 

 both sexes of a pretty dragonfly new to Costa Rica. It may 



