84 ANNALS OF SCOTTISH NATURAL HISTORY 



Bund, Major Traherne, Dr. Francis Day, and some of our 

 Fisheries Commissioners ; but it seems to me few later writers 

 have built upon these bases, except in so far as trout and 

 hybrid Salmonoids have been observed under more or less 

 artificial conditions. 



I must leave over for the present an account of stocking 

 certain previously fishless streams and lochs, and their 

 subsequent history. 



DIPTERA SCOTICA: I. PERTHSHIRE. 

 By PERCY H. GRIMSHAW, F.E.S. 



WITH a view to furthering our knowledge of the distribution 

 of Diptera in Scotland, I propose to publish from time to 

 time, according to the opportunities which present them- 

 selves, county lists extracted from the notes which have for 

 some years been accumulating in my register of specimens, 

 I shall also supplement these lists by references to records 

 published elsewhere, and by adopting this method I hope in 

 time to be able to furnish a complete account of our know- 

 ledge of the subject. For my purpose I have considered it 

 better to adopt political divisions rather than the more 

 natural areas founded upon river drainage, though I shall 

 probably by this plan lay myself open to the criticism of 

 many lovers of " faunal areas." With animals possessing 

 such perfect locomotive powers as we find in insects it seems 

 to me to matter little what basis of division is adopted, as 

 the natural boundaries in a small area like Britain can only 

 offer the very slightest impediment to the spread of species, 

 At any rate, a more precise idea of distribution can be 

 gained by the adoption of county boundaries than by taking 

 the much larger areas defined by nature. 



In publishing these records, considering the very deficient 

 nature of our knowledge of the distribution and times of 

 appearance of Diptera, I have thought it better to give full 

 details of localities and dates of all species, even the 

 commonest, as it is only by this means that we can gain a 

 really accurate idea of such subjects. I shall number the 

 species consecutively and separately for each county, and in 



