SOME CONblDEKATlONS CONCEIJNING Ml.MlCRV, ITt 



Figure V. — The larva, t'ull-growu (ready to pupate) unclothed — (a) the special 

 tubercles, (b) discs and hairs on lower parts of some segments. 



Figure VI. — The first abdominal segment with its special tubercle. 



Figure VII. — The special tubercle on ventral margin of oth abdominal segment 

 much enlarged. 



Figure VIII. — Discs and hairs, "ind abdominal segment. 



(To be concluded.) 



Some Considerations Concerning Mimicry. 



By WILLIAM -I. KAVE, F.E.S. 



Early in 1901 I went out to British Guiana to study the 

 magnificent lepidopterous fauna of that region. Quite one of the 

 most striking things seen was the wonderful similarity of a number of 

 species of different genera, and even different families. It was not 

 one group only (although one group was by far the most conspicuous), 

 but a number of cases presented themselves where species were like 

 other species of different genera and different families ; butterflies 

 sometimes even closely resembled moths. The main group consisted 

 of Danaine, Heliconine, Ithomiine, and Erycinid species, the remark- 

 able characteristic of the whole being a ground colour of ochreous- 

 brown, with black and yellow markings, the hindwing with a tendency 

 always for the black markings to spread and even to cover the whole wing 

 area. ^Vhen forced to leave owing to malaria, at the end of little more 

 than three months, I was fortunate in finding a man who was willing to 

 collect for remuneration, and now, with the whole of his and my own 

 material together for study from one single road or track stretching 

 from about 170-1H6 miles from the coast, one can form some idea of 

 what species really do occur together. It is now roughly possible to 

 determine the proportions in which these insects occur, which must 

 be one of the fundamental points on which to decide " which species 

 have been dominant ?" It has been argued, and perhaps justly, that 

 possibly tbe influential species (influential by being abundant and at 

 the same time distasteful) is not abundant now, and that it, like so 

 many other species, has its periods of greater or less length when it is 

 abundant ; at others, not so. Be this as it may, the statement is 

 probably true that if a species is distasteful onti always abundant, it 

 will exert an influence over other species that are not common, and, 

 therefore, not readily remembered by birds — their enemies. tSuch a 

 species in British Cruiana is MeUncn'a iiinnur. It will matter little 

 whether the uncommon species somewhat resembling it are palatable 

 or not ; each might become the central flgure if its numbers Avere to be 

 suddenly largely increased to make it an exceedingly abundant species. 

 Where three, four, or even more species of one genus occur, they are 

 from the very nature of tlieir relationship near together, and, if they 

 have not diverged much in coloration, they may all act in concert as 

 the patterns, each drawing such other species as may be nearest in 

 colour and markings. Mdinaea ninemc has on the Potaro River at 

 least two other species — .1/. crameri, M. eijina — which are conge- 

 neric, and it is more than likely that each has done its share in 

 attracting or indirectly drawing others, though one year M. innnnc 

 may be more influentuil by its numbers, another year M. oiina, and 

 SO on. The species which are being compelled by stress of selection 



