( xxxvi ) 



structural phenomena presented by them (e. g. seri-ated inner 

 margins, pectiniform rows of spines and bristles, brush-like 

 pilose fascicules, etc.). He should be glad to hear of any 

 observations that might have been made as to the structure 

 and functions of calcaria in insects of other orders, having 

 examined them himself only in the Hymenoptera. 



Dr. F. A. DixEY exhibited male and female specimens of 

 the African Pierines Belenois ih>/sa, Hopff, and Mylothris 

 agathina, Cram. He drew special attention to the fact that 

 the resemblance between these two species, which Mr. Trimen 

 speaks of as " deceptively close in both sexes," applies mainly 

 to the dry-season phase of the Belenois and not to the wet. 

 This, he observed, was well illustrated by the exhibit, which 

 included wet and dry-season examples of both sexes of 

 B. thysa; M. agathina showing no seasonal change. The 

 resemblance borne by the male Belenois to the male Mylothris 

 was much more striking in the dry-season specimen of the 

 former than in the wet ; and while the dry-season female 

 B. hysa was an excellent copy of the female M. agathina, it 

 was seen that the usual wet-season form of the same sex did 

 not mimic the Mylothris at all. These facts appeared to be 

 significant in relation to the comparative scarcity of insect 

 food during the dry or winter months, and the consequent 

 greater liability of dry-season forms to the attacks of enemies. 

 The higher need for protection thus experienced by the dry- 

 season forms had been clearly shown by Professor Poulton, 

 who had found in the principle referred to an explanation of 

 the cryptic garb assiimed in the dry season by several species 

 of Precis (Trans. Ent. Soc. Lend., 1902, pp. 432^443). Other 

 examples of the same phenomenon had been subsequently 

 adduced by the speaker, who had also brought evidence to 

 show that it was especially characteristic of the female sex 

 (Ibid., 1903, pp. 155-158, PI. vii.). But the present instance 

 differed from all these in the fact that the protection enjoyed 

 by the dry-season phase took the form not of cryptic coloia- 

 tion but of mimicry. Tlie species of Mylothris were held on 

 good grounds to be distasteful, and Mr. G. A. K. Mai^shall 

 had expressed the opinion that B. thysa was a Batesian mimic. 

 Tliis might be so, but the speaker rather inclined to the view 



