JUAN VINAS— AROUND THE LAGUNA i8l 



with ditches of running water which the ants are unable to 

 cross, by flooding the nests and hy exploding them with 

 carbon-bisulphide. The latter is said to be the most suc- 

 cessful method yet devised. On December 2 the leaf- 

 cutters were crossing the railroad west of the crater and 

 another busy column was marching along the horizontal 

 roadway. 



A third nest was under the road ascending from the sta- 

 tion toward the village and had several openings in the road- 

 bed and from these, on August 2, ants were emerging, some 

 carrying pieces of leaves which had been previously taken 

 into the nest. These pieces were carried five or six inches 

 from the openings and dropped on the pellets of earth which 

 were likewise brought up by the ants in much greater num- 

 ber. I examined two of these leaf pieces under my lens but 

 could find no cause for their rejection. Reasons mentioned 

 by Belt in his account of this action {Naturalist in Nica- 

 ragua, 2nd edit., p. 82) did not seem to apply, as no rain had 

 fallen during the day, nor did the pieces appear in the least 

 withered; one had what looked like fungus marks acquired 

 while on the tree, but the other did not. 



Still another rather small nest was alongside of the rail- 

 road tracks within the crater but east of the station. On 

 passing it on September 29, I noticed two blue-black wasp- 

 like insects running over the top of the nest, one of which 

 entered an opening and entirely disappeared from sight. In 

 a short time it came up, walked about a little and went 

 down again, not to reappear as long as I watched. Two 

 leaf-cutters came out of this opening at intervals after the 

 visitor had gone down the second time and were apparently 

 unconcerned. Later I caught the other of these two blue- 

 black insects, which proved to be a fly {Eristalis scutel- 

 laris), whose manner of walking, of flying and of folding the 

 wings down over the back of the abdomen is like that of a 



