128 Mr. G. F. Scott-Elliot on Floicer-Haunting Diptera. 



On the other hand, I am far more certain of the depend- 

 ence of flowers on insects than I was before. When 

 such minute forms as Draha verna, Siihnlaria aqnatica, 

 or such " typical wind-fertilised " species as the Burnet, 

 Salad Burnet, and Dog's Mercury, and species of such 

 genera as ThaUdrum and Planfago are found to be 

 visited by insects, as I have myself seen in the course of 

 my work, it leads one to doubt if wind-fertilisation is 

 ever of much use. A simple mathematical proof shows 

 that the chances of a piece of pollen from one flower 

 reaching that of another growing within a foot of it, is 

 about one to three hundred; but if an insect is on one 

 flower, for any purpose, the chance that it will go to the 

 next visible flower is probably ten to one. 



It seems to mo that these Diptera will probably yield 

 the most valuable results in investigating the origin of 

 plant species, for they visit all kinds of flowers, and 

 possess both colour-sense and intelligence, as I have 

 tried to show. In fact, it is to them that we probably 

 owe all the neatly made, small and bright-coloured 

 forms which are particularly abundant in this country. 

 It is not possible now to say definitely, that this or that 

 insect is responsible for such a flower (though I think, 

 myself, I could say it for certain forms) ; a genus in 

 which seven species have been studied by us, and 

 on which we have found hive bees and bumbles in all 

 cases except two, would imply a very high botanical 

 structure. Yet this genus is Hijpericum, the flowers of 

 which are very simple. 



Still I think from my own experience, there can be no 

 possible doubt either that the flower has modified the 

 habits and structure of the insect, or that the insect 

 has modified the habit and structure of the flower. Of 

 the two, it seems to me, as a botanist, that the flower 

 has been the predominant factor ; but this opinion may 

 be the result of prejudice. 



Note. — j\Ir. G. H. Verrall, who has kindly looked through this 

 paper, says that it is difficult to distinguish Emph cltripennts from 

 about twenty closely allied species, several of which are yet un- 

 recorded as British ; that Eristaliif jiert'tnnx has never been clearly 

 differentiated in print, and that both Syrphus chictellus and 

 S. ribesii are very difficult to distinguish from numerous allied 

 species. — H. G. 



