218 [March, 



Pontresina itself lies at an elevation of 5915 feet, and the district 

 explored by me occupies about ten miles in various directions there- 

 from, and at from 5600 ft. to 6S00 ft. in elevation. The return 

 journey was via the Julier and Schyn Passes (arrangements having 

 been made, in the meantime, for the conveyance of passengers and 

 their belongings on an improvised raft across the river at Keichenau), 

 and the highest point at which any Trichopterous captures were made 

 was at the little inn on the summit of the Julier Pass (7503 feet) 

 during the short time the diligence stopped. 



The principal hunting-grounds were the Val Eoseg as far as the 

 glacier ; the Lake St. Moritz, and the Statzer-See (in the wood) 

 which discharges into it ; the Val da Pain (no doubt a paradise for a 

 Lepidopterist, but practically useless for my purposes, owing to the 

 utter absence of trees and the snow-fed stream) ; the wild rocky 

 ground in a forest of larch and arolla {Finns cernbra) through which 

 the torrent from the Piz Languard finds its way ; a nearly similar 

 locality on the right of the road to Samaden ; the Val Celerina (in 

 which are magnificent old larches) ; and the Val Bevers. 



In my " Eevision and Synopsis of the Triclioptera of the European 

 Pauna," Appendix, p. xciv, I pointed out the deterrent effects of the 

 vicinity of glaciers on aquatic insect-life. Those remarks came before 

 me very vividly on this excursion. The stream at Pontresina, termed 

 the Platzbach, is utterly devoid of Trichopterous life, being poisoned 

 by the Eoseg and Morteratsch glaciers, but above the latter it is pro- 

 ductive. A glacier-fed stream is turbid and milky ; a snow-fed stream 

 is usually clear and blue after the spring and early summer meltings 

 are over, but even such a stream as this is seldom very productive, 

 unless it is also largely fed by lateral rivulets from land springs, and 

 these latter are the best of all. Naturally, in such a district these are 

 not abundant, and long distances must be travelled over for their 

 discovery * 



The results of my excursion were about 450 specimens, repre- 

 sented by the species enumerated below. Eather to my disappoint- 

 ment, no species that can absolutely be identified as new was dis- J 

 covered ; but some purely alpine forms were abundant ; still, however, - 

 not so great a number of species were taken as I had anticipated 

 finding. There was a marked absence of those small forms usually 

 so abundant in lower districts where the water is warmer. The 



* Geological conditions also infl nee aquatic insect-life. Limestone districts are probably 

 the best. Schist is fatal : perhaps the most remarkable instance of this is to be seen at Thusis, 

 where, in consequence of schist, the Nolla, at its junction with the Rhine, ia of inky blackness, 

 and useless for entomological purposes. 



