( 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.)
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