298 ENTOMOLOGICAL NEWS. [July, '15 



landslide had occurred changing their positions very greatly. 

 We ascended a short distance to reconnoitre and saw that 

 some small trees had fallen, blocking our usual path, while 

 rocks larger than one's body had been rolled down, many of 

 them being quite unstable. In fact the change since the 26th, 

 when we were here, was far greater than at any time during 

 the preceding ten months in which we had known this fall. 

 We concluded not to ascend on account of the risk involved 

 and went on to the farther waterfall where two good-sized 

 Thaumatoneura larvae were obtained, one of which transform- 

 ed as a female before we left the fall. We subsequently learn- 

 ed that on April 28, when we were in a different locality, two 

 distinct falls of rock, with the sound of crashing of tree 

 branches, were heard in the direction of the higher waterfall, 

 accompanied by the odor of newly-disturbed forest earth. It 

 was our good fortune that this landslide did not occur until 

 after our ten months' search had been crowned with success 

 and we could smile at the efforts of the Genii of the Fall to 

 veil the secret of Thaumatoneura from us. 



To make our larval record complete one was secured on 

 May i at a third waterfall, near the iron bridge over the Rio 

 Reventazon, 800 feet below the railroad. 



The habit of dwelling in and around waterfalls and cascades 

 which we have described for Thaumatoneura, larva and adult, 

 and which is also the habit of Argia talamanca associated 

 with it, does not appear to have been mentioned for any other 

 Odonata. Yet it is likely that such a habit will be found to 

 exist in some other members of this group of insects, espe- 

 cially in the tropics of the Old World, where topographic and 

 climatic conditions similar to those of Costa Rica prevail. In 

 countries where frost occurs the low temperatures incident to 

 this phenomenon may prevent the survival of Odonate larvae 

 in waterfalls of small volume, where the water is spread out 

 in a sheet of but a few centimeters in depth, as is the case in 

 those falls which Thaumatoneura inhabits. On the other 

 hand, the force exerted by falling water in large volume may 

 be too great to permit Odonate larvae dwelling therein. 



