JUAN FIN AS— THE WATERFALLS 1 93 



overhanging vegetation. The fluctuations in volume of 

 this fall were very slight. 



It was in or at the foot of one or other of these two water- 

 falls that we found the transforming larvae of certain dragon- 

 iiies, — Thaumatoneura, Argia talamanca, Philogenia carril- 

 lica and Palcemnema — of whose habits and early stages 

 nothing had been known previously. From our observa- 

 tions here and elsewhere in Costa Rica it appears that Thau- 

 matoneura and this Argia are exclusively waterfall-dwellers, 

 but that Philogenia and Palcsmnema live in other situations 

 also. 



Standing at the bottom of the nearer waterfall on June 24, 

 and looking up, I could see the males of two supposed species 

 of Thaumatoneura fluttering through the spray, chasing each 

 other or alighting upon the rocks or plants. One species 

 {inopiyiata) had a blackish-brown band across the middle of 

 each wing, the other (pellucida) had uncolored wings. So 

 heedless of the spray were they that it gathered in little 

 drops on the wings or hung suspended from the hind end of 

 the body. 



On this and following days we observed the mating of 

 Thaumatoneura. The female had not hitherto been known; 

 it has the tips of all the wings black and hence can be easily 

 distinguished from the male even at a distance. Both 

 sexes are large and conspicuous insects, having a wing- 

 spread of four inches. While mating the male held its 

 wings horizontal and expanded, those of the female being 

 vertical and folded together. At the end of ten minutes 

 the male released the female and at the same instant folded 

 his wings together into the vertical position. The female, 

 losing her attachment to the male, assumed a position a 

 little below him on the same twig or rock. Subsequently 

 she flew away to begin egg-laying. 



We watched supposed egg-laying in three or four cases. 



