8 MR. H.J. ELWES ON THK GENUS i'ARNASSlUS. [Jail. 19, 



ample, in another 100 pairs may be insufficient to illustrate all the 

 points in the history of a species. 



With respect to the development and function of the pouch in this 

 genus, which appears to me interesting not only to le])idopterists but 

 to all students of Biology, I must here acknowledge the assistance I 

 have received from Mr. A. Thomson, of the Society's Gardens — who 

 undertook and carried out in a most jiainstaking manner the obser- 

 vations on living insects, of which an account is given below — 

 and especially to Mr. Salvin and to Prof. Howes, of the Biological 

 Laboratory, South Kensington, who undertook the difficult and 

 delicate task of dissecting and examining the specimens preserved 

 by Mr. Thomson at the Gardens. 



And though much remains to be done before we can say that we 

 fully understand this intricate question, yet a distinct advance has 

 been made on our previous knowledge, and certain facts which were 

 previously doubtful or obscure have been proved. The first writer 

 who seems to have paid much attention to this organ was Yon Siebold, 

 who published in the ' Zeitung fiir wissenschaftliche Zoologie,' 1850, 

 iii.pp. b4-Q\, and reprinted in the 'Stettiner entoniologisciie Zeitung' 

 1851, pp. 176-185, a long aud most valuable paper on the subject, 

 aprecis of which, from an English translation kindly lent ine by Mr. 

 Gosse, I am here able to give : — 



The first part is historical, and shows that though Linnaeus, 

 Latreille, and SchaflPer had mentioned tlie existence of the ponch and 

 described its form more or less incompletely in P. apoUo and P. mne- 

 mosyne, no one had carried these observations any further. Ochsen- 

 heimen accepts its existence in the female as a generic character of 

 Doritis, and Boisduval separates Doritis apoUinus from Parnassius 

 because it has no pouch. 



Siebold doubted whether the organ really formed [)art of the 

 body, as he found that he could easily separate it in P. mnemosyne, 

 and, with more difficulty, in P. apollo, as in this species it is glued 

 more strongly by its base to the underside of the abdomen. 



He then suggests that it originates during copulation, in these 

 words : — " Probably from the male or female individual, at the anal 

 region there is secreted a clammy coagulable fluid, poured forth 

 during the close association of the genital organ of the male with 

 that of the female, which, by coagulating and hardening, produces a 

 firm and long-enduiing union of both sexes. After the end of the 

 copulative act, and after tiie complete severance of the sexes, there 

 remains this coagulated substance as a sort of cast or impress of the 

 hinder parts of the male in the vicinity of the sexual orifice of tiie 

 female, a witness of the accomplished coitus." He then states that 

 virgin females fresii from the pupa have no pouch, and says that 

 Hoger was mistaken when he suggested that the pouch was after- 

 wards protruded from the body for the purpose of oviposition. He 

 then goes on to state that a chemical exnuiination of the substance of 

 the pouch by Dr. Baumert showed that it had no affinity witii the 

 chitinous substance of the body of the insect, which was insoluble 

 when treated witli caustic alkali ; whereas the pouch of both P. apollo 



