184 Mr. H. Scott on 



an exceptional drought had prevailed for some time. By 

 climbing on to the ledges, access Avas obtained to the smooth 

 cliff-faces, which were covered in places with great numbers 

 oF the larvcC, these ap[. earing dark against the grey back- 

 ground of rock. As has been found by previous observers, 

 the larvte, when disturbed, shift their position slightly with- 

 out becoming detached from the rock. Considerable difficulty 

 Avas experienced in collecting them, because, when detached, 

 they were so easily and rapidly swept away hy the swift- 

 falling water. 1 did not then know of the method of col- 

 lecting such larvae employed by Dr. Lutz in Brazil. He 

 states {op. cit. p. 82) that if they are covered with the hand 

 and rolled slightly to and fro, they loosen themselves from 

 the rock and fix themselves firmly by their suckers to the 

 collector's hand ; thus a number may be collected in a short 

 time. Still greater difficulty w as experienced with the pnpffi : 

 these are cemented to the rock by their adhesive pads, and 

 when force was used they broke loose suddenly and were not 

 easily caught Ijefore being swept away. In such a situation 

 as this, it is not hard to imagine how rapid the unfolding of 

 the wings must needs be on the emergence of the imagines, 

 if any of the latter are to avoid being canglit by the rushing 

 water — a rapidity of unfolding provided for, as is well known, 

 by the wings being already developed to their full size in 

 the pupa, a condition which necessitates a complex system 

 of folding, which in its turn produces the ''secondary 

 veining'^ so characteristic of the family. 



Besides the Bh pharocerid larvse there Avere on the steep 

 rock-faces some Simuliid larvae, also curving tubes composed 

 of web and grains of sand, inhabited by larvae of a Psycho- 

 myid caddis-fly. Small caddis-flies Avcre flitting iu shady 

 places over the surface of the falling Avater, and occasionally 

 settling on dry rock close thereto. Some of these were 

 ca|)tnred, and have been described by G. Uimer''^ as Melano- 

 trichia msularis, a new species of Psychomyid ; they are 

 considered by him to be the imagines of the tube-inhabiting 

 larvae. 



The vegetation bordering the stream beloAV the fall was 

 SAvept iu the hope of obtaining imagines of the Blepharo- 

 cerid. As has been said, this hope was not then fullillcd, 

 but specimens were obtained of a fly of such remarkable 

 appearance that at first sight it was thought to be the special 

 object of search. It |)rovfd, however, to be a Myeetojjhilid 

 of the curious genus Lyyisturrhinu ( = ProbuIa;us), and has 



« Duutsch^i eiit. Zeit-^chr. 1913, p. 366. 



