32 PERCY SLADEN TRUST EXPEDITION 



may not be absolutely confined to it, so that such places are tenanted by a fairly definite 

 fauna of their own. Another remarkable locality several times visited was the summit of 

 Mount Sebert. This consists in great part of bare granite, but it has patches of a very 

 peculiar stunted forest growth, and it yielded valuable entomological material. 



Another excellent and often-visited collecting-ground was a valley in the forest, some 

 way above the Cascade house in the direction of Mount Harrison. It was an exceedingly 

 beautiful place, traversed by a clear mountain-stream, and filled with a thick wood of 

 native palm-trees bearing a luxuriant growth of epiphytes. Here were found many 

 small and minute Coleoptera, certain very minute and curious Hemiptera, etc., among 

 the dead and fallen palm-leaves ; Diptera and other insects by sweeping ferns and other 

 undergrowth ; while over the stream flew mayflies and another new species of caddis-fly 

 (Hydromanicus seychellensis Ulmer). 



At this time was experienced the worst spell of weather, and almost the only 

 successful night-collecting, during the whole of my stay in the islands. The season was 

 that in which most rain is expected, and from December 19 to December 30 the sun was 

 scarcely to be seen at all at Cascade. There was also heavy rain at other times, and 

 collecting was frequently rendered very difficult or temporarily impossible. The weather 

 was generally calm : on fine days the sea lay smooth as glass under a blazing sky, and a 

 great mass of white cloud hung motionless over each of the distant islands of Praslin and 

 La Digue. Although a large number of Lepidoptera had already been secured by diurnal 

 collecting, yet the night-flying species had not been obtained hitherto in any satisfactory 

 quantity. This defect was made good to a large extent during the wet weather at 

 Cascade. By placing a bright lamp and a sheet in the front of the verandah on dark 

 cloudy nights, we succeeded in getting a number of the larger moths, including many 

 species new to me. For example, on December 26 about 111 specimens were captured, 

 on December 27 about 40, and others on other nights. On clear and moonlight nights 

 none were obtained. 



It has been mentioned that we largely concentrated our attention on Diptera. 

 During the wet weather especially, numerous small flies and other insects came into 

 the house and were caught on the window-panes (Drosophilidse, Phorida?, Chironomidae, 

 Psychodidse, etc.). Moreover here as elsewhere Diptera were collected in the high 

 forests. Many flies were captured in the plantation, where certain species had the habit 

 of settling, in fine weather, on the leaves of various cultivated trees and bushes. Among 

 these last were certain metallic Dolichopidas ; it could often be remarked that different 

 forms of these flies showed each a distinct predilection for a certain kind of spot on 

 which to settle. Thus, in the high forests there is a particular kind of Dolichopid 

 (Leptorhethrum sp.) constantly seen to settle on the broad upper surfaces of the leaves 

 of Curculigo or of small palms ; while on the plateau of the Mare aux Cochons in 

 Silhouette a brilliant metallic-green form continually settled on the big leaves of the 

 climbing Ip>omcea, often in the blazing sunlight. It may be well, too, to mention here 

 a phenomenon several times seen in the mountain forests. There are small flies 

 (Limnobiidse, almost certainly Thrypticomyia sp.) which hang in rows to threads of web 

 fastened between bushes. Each fly clings to the thread by its two front tarsi : a dozen 



