112 A YEAR OF COSTA RICAN NATURAL HISTORY 



ley I was almost at the very foot of this huge slide — an al- 

 most vertical face of yellow rock perhaps three hundred 

 feet high and a hundred wide, not reaching as far down as 

 the valley floor. On one side of the floor was the Laguna 

 del Dirumbo (also called Laguna del Reventado and Laguna 

 de los Derrumbaderos), the source of the little Rio Reven- 

 tado. The laguna was about eighty feet wide and one hun- 

 dred feet long, of clear cold shallow water. Here and there 

 beds of grass dotted its area, and its undefined and swampy 

 sides were bordered by trees and bushes. Around the la- 

 guna were many oaks both alive and dead, the whitened 

 trunks of the latter giving a curious and mysterious effect, 

 and among the oaks some clumps of bamboo and much 

 grass. Below the laguna cattle were feeding, the part oc- 

 cupied by them being separated by a barrier or fence of 

 dead logs and branches. There were several smaller boggy 

 streams in addition to the Reventado and a second smaller 

 swampy spot. The altitude of this place was 9100 feet by 

 my aneroid. There were very few insects in this valley and 

 to my astonishment and disappointment not a dragonfly 

 could I see. In July, 1906, I had a similar experience at 

 Lake Moraine on Pike's Peak in Colorado, at a not very 

 different elevation. Indeed the highest altitude at which 

 we personally met dragonflies in Costa Rica was below 

 Tierra Blanca at about 6450 feet. 



Prof. J. Fidel Tristan visited the Laguna del Reventado 

 in July, 1910, and soon after wrote me that he had seen 

 "three big dragonflies flying on the laguna. They were of 

 a dark color and I tried to catch them but my efforts were 

 not enough." In April, 191 1, he was more successful and 

 took a single specimen in a rivulet near the laguna. This 

 specimen, a male of Argia terira, a small slender blue and 

 black species, furnishes the present record for the highest 

 altitude for Odonata in Central America. 



