on Floiver-Haiinting Diptera. 119 



tion, remembering tlie foregoing hint, is mentioned chiefly 

 in order^ if possible, to get some information from those 

 present at this Meeting. I have come to the conclusion 

 that the majority of Diptera have a recognized space up 

 and down which they are continually flying. I have 

 frequently had to remain as quiet as possible for three 

 hours beside some interesting flower, and on these 

 occasions I have seen the same fly perpetually flying up 

 and down within perhaps 10 or 15 yards, occasionally 

 stopping to rest and then resuming its patrol. For the 

 carrion flies the phenomenon is veiy easy to observe, 

 and I fancy that the whole country is really marked out 

 into beats for each individual or pair. If a piece of 

 carrion or excrement is deposited on a particular spot, 

 it is astonishing that it should be so soon covered by 

 hundreds of Lncilia Caesar, Scatophaga, etc. In fact, 

 I have a strong suspicion that these creatures divide the 

 ground in the way that vultures do in tropical countries, 

 and that when the first one detects the smell, the 

 difierence in his flight or his absence from his proper 

 place tells that in the next beat, and so on ; the know- 

 ledge is thus conveyed with astonishing rapidity from 

 beat to beat, and crowds continue to flock in until the 

 first comers are satisfied and fly back to their places. I 

 mention this as the result of observation, though not by 

 an entomologist, and chiefly with a view to extracting 

 information. The importance of it will be obvious with 

 regard to the question of isolation already mentioned, for if 

 every fly, or at any rate, most of the flower-haunting species 

 usually remains or remain in the same small locality under 

 ordinary conditions, it is obvious that there is practical 

 isolation in very circumscribed habitats. The larval 

 forms of Diptera and the plants on which they feed seem 

 to be very little studied, and this is also of great impor- 

 tance to botanists, because I fancy that this has a great 

 deal to do with the occurrence of flowers in great 

 numbers at definite places. Thus on the bare wind- 

 swept low-lying seashore, between the Annan and Kirtle, 

 I found the Diptera very few in number and particularly 

 limited in species. Such flies as Lucilia, Anthomyia 

 radicum and Chortophila, appeared to fertilize most of the 

 seaside plants. On the other side of the Solway, 

 where there are cliffs, and these are interrupted by 

 bays and many small burns, the abundance of 



