on Flower-Haunting Diptcra. 127 



In words this may be translated to mean that these 

 Diptera are, on the whole, more intelligent than the 

 lower class Hymenoptera. 



Three species of Diptera visit species of Orchidacea?. 

 In fact, Sijrphus rihesii, Eristalis pertinax, and Empis 

 vitripennis, appear to be the main agents in effecting the 

 fertilisation of our common British forms. The only 

 other insect which I have myself as yet discovered on 

 these plants is Argynnis aglaia ; my friend, Mr. Arm- 

 strong, however, reports that he has observed certain 

 " large brown and sulphur moths " feeding on Hahenaria 

 h if alia. ^ 



Nine of these Diptera are found either on the larger 

 Leguminoase , flowers of the Bugle type, or on Orchids ; 

 and this is sufficient to show a very considerable amount 

 of intelligence. 



It is not easy to bring these insects into any series 

 which will show their relative abihty, but judging from 

 the preceding table, the following is a pretty sound 

 grading of their intelligence : — 



Class 1. Bombus. 



„ 2. Empis vitripennis, Eristalis pertinax, 8i/rphiis 



rihesii. 

 „ 3. Empis livida, Melanostoma, Platychirus alhi- 

 manus, P. clypeatus, P. peltatus, RJiingia, 

 Allantus. 

 ,, 4. Remainder, including Andrena albicans. 



It remains to point out the bearing of the foregoing 

 remarks on the use of Diptera and other insect visitors. 



I have not found any confirmation of certain theories 

 which suggest that the actual probing of an insect's 

 proboscis, or the friction of its feet have any influence 

 in determining the growth of hairs, or the flow of sugar 

 to that particular part of the flower ;t it is, of course, 

 probable that the continual draining away of nectar from 

 a certain spot will induce a larger supply to come to that 

 particular position, just as the continual use of a certain 

 muscle will produce a greater enlargement of it. It is 

 even probable that such a demand for nectar may be 

 inherited, but this is not yet proved. 



* I have taken specimens of Leucania turca in the New Forest 

 with the pollinia of this species attached to their heads. — H. G. 



t The researches of M. Kustenmacher on Galls, Bot. Gaz., xx., 

 p. 497, are, so far as hairs are concerned, rather against this view, 

 which is not, to my knowledge, supported by any direct evidence. 



