lf'09]. 141 



would lead to the view that mimetic approach would be one-sided only, that is, from 

 a weaker species towards a stronger and even in an ojiposite direction ; further, that 

 when the relative dominance of the two species was equal the mere operation of 

 MiilJer's factor would produce no mimetic effect, until some other factor had first 

 produced a condition of inequality. On this view mimetic interchange would never 

 be mutual and simultaneous, but would only result from a complete reversal of the 

 relative dominance of the two species during the production of the mimetic resem- 

 blance. For this process he had suggested the name of Alternate Mimicry. The 

 author was also compelled to reject entirely Dr. Dixey's new hypothesis as to the 

 "function of the double aposema," because it completely left out of consideration 

 the differences and resemblances between the various forms regarded from the 

 standpoint of general facies. Dr. Dixey stated that he did not consider the Presi- 

 dential rhair a proper place in which (o reply to Mr. Marshall's criticism, and that 

 he would therefore deal with the points at issue on some future occasion. Mr. 

 C. J. Gahan very strongly supported the opinions advocated by Mr. Marshall, and 

 expressed the view that while Dr. Dixey professed to support Miillerian mimicry 

 yet his defence of Recipr cal Mimicry really constituted a severe attack upon that 

 theory. Mr. S. A. Neave said that as a result of his field experience in Africa he 

 was unable to accept the theory as to the function of " double aposemes," but he 

 did not mean thereby to imply that he rejected every case of Reciprocal Mimicry. 

 He suggested that Alternate Mimicry might not be so uncommon a phenomenon as 

 Mr. Marshall appeared to think. Mr. Tutt, Mr W. E. Shnrp and Professor 

 Hudson Beare also made some brief comments on the subject. 



Wednesday , May oth, 1909. — The President in the Chair. 



Mr. S. A. Neave, exhibited three specimens of an OEstrid fly belonging to the 

 genus Spafhicera, Corti, ca]itured on the carcase of a rhinoceros shot by him near 

 Fort Jameson, N.E. Rhodesia, in February, 1908. He pointed out the extreme 

 rarity of individuals of this genus in the imago state, though the ffistrid larvae had 

 long been known and frequently recorded in the intestinal canal of Rhinoceros 

 bicornis, and recently Professor Sjostedt had succeeded in rearing one individual 

 from a larva, described by him under the name meruenaift. Mr. H. St. J. Donis- 

 thorpe, examples of Formica exsecfa, Nyl., from Parkhurst Forest, Isle of Wight, 

 and from the same locality the beetle Dinarda hagensi, Wasm., hitherto only 

 observed (with the same ant) in Britain at Bournemouth by the exhibitor ; also 

 Tetramoferia donisthorpei, Kieffer, n. sp., and T. femoralis, Kieffer, n. sp., taken by 

 liimself with Tetramorinm cxspitum, Ti., at Whitsand Bay, Cornwall ; Paracletes 

 cimiciformis, taken with T. ccespitum, L., at Rame Head, Cornwall; and Antenno- 

 phorus puhesceiis, Wasm., a species new to Britain, taken on Lasius Jlavus at 

 Whitsand Bay. Mr. W. E. Sharp, examples of the following Coleoptera from 

 the West of Ireland to illustrate the prevalence of our colour variation in the 

 direction of melanism in that region : — Carahm nemoralis, Miill., C. gramdatus,'L., 

 C. arvensis, F., Notiophilits aquaticus, F., N. biguttatus, L., Leistus ferrugineus, L., 

 and Corymhites cupreus var. xruginosus, F. Mr. H. St. J. Donisthorpe also showed 

 specimens of Carabus tiitens, C. aroensis,M\A. Pteroslichus dimidiatiis from the New 



