JUAN VINAS— AROUND THE LA GUN A 183 



feet lower than Cartago. On March 14 we rode east of 

 Cartago primarily to capture ant pictures, but we saw few 

 active trails except in deep shade or confused with vegeta- 

 tion. On the road near Las Concavas we photographed a 

 large nest with half a dozen conical openings like little vol- 

 canic craters, over a foot high. We attempted a picture of 

 a bridge composed of sticks and branches by means of which 

 the ants were crossing a little rivulet. But every attempt 

 to clear away intervening vegetation and let in more light 

 caused the ants to slip over to the darker side of the bridge, 

 so that their *'bashfulness" — (or negative heliotropism.^) — 

 kept most of them out of the pictures. On the Pacific side, 

 a large and active column of leaf-cutters was observed on 

 the carretera nacional between El Alto and Tres Rios at an 

 altitude of 4650 feet, on March 17, and we have specimens 

 from Alajuela dated September 9. These last two lots 

 represent another species, j4tta {Acromyrmex) octospinosa, 

 whose differences from cephalotes may be seen very easily 

 from the accompanying photographs. 



