( 117 ) 



V. Notes on Flower -Haunting Biptera. By Geoege 

 Fkancis Scott-Elliot, M.A., B.iSa, F.L.S., etc., 

 communicated by Herbert Goss, F.L.S. 



[Read February 10th, 1896.] 



I HAVE recently been enga^^ed in writinf^ a Flora of 

 Dumfriesshire, and on beginning, it seemed to me advis- 

 able to make a new departure in several respects from 

 the plan usually followed in such works, which is 

 practically that of the late Mr. Hewett C. Watson drawn 

 up in 1851. Amongst other points I have thought it neces- 

 sary to observe insect visitors, and for this reason. The 

 entire dependence of most flowers on their insect clientele 

 for fertilisation has been proved over and over again, 

 and therefore it follows that to understand the distribu- 

 tion of species in any small area, it is necessary to know 

 the insects which visit the species in that area. More- 

 over there are many theories at present abroad as to the 

 origin of variations by natural causes, and as most 

 botanical characters depend on those parts of the flower 

 which are adapted to insects, the importance of a know- 

 ledge of these latter can scarcely be overrated. 



Besides their importance in this respect, as being a 

 possibly direct agency in the origin of variations in 

 plants, insects must play an enormous indirect part in 

 the isolation of flowers. If flowers of the same species 

 are growing partly inside a sheltered and shady wood 

 and partly on the bare ground outside that wood, it 

 seems to me, from my own observations, that they will 

 most certainly not be visited by the saine insects. It is 

 not improbable that a Bombus or hive bee, or possibly 

 a butterfly, will visit both the forms outside the wood 

 and those within it ; but I do not think 1 am at all rash 

 in saying that probably not 5 per cent, of those outside 

 will be fertilised by pollen from those inside the wood, 

 and vice versa. This means, for reproduction, nearly 

 perfect isolation, and, therefore, just as we iiud in the 

 case of oceanic islands, the formation of new varieties 

 may proceed indefinitely. 



TRANS. ENT. SOC. LOND. 1896. PART I. (oOth MARCH.) 



