always in countless swarms, while the mimic is a hundred times more 

 rare ? Does not the model bear the hereditary colouring of its genus and 

 family, while the mimic appears in borrowed plumes? And, finally, is not 

 the model unpalatable on account of its repulsive taste and odour, being for 

 these reasons safe from foes, while the mimic finds protection in its disguise, 

 without which it would be devoured as a tasty morsel ? It is much to be 

 regretted, however, that all these characters sometimes leave us in the lurch. 



" The imitating species may, at least in some districts, be more common 

 than its model. If both the latter and its mimic extended into a new 

 district the conditions might be more frequently unfavourable to the model 

 and favourable to the rarer species, and thus the original proportional 

 numbers might be reversed; indeed, this may happen, in course of time, 

 in the old habitat of the species. In the province of Santa Catharina, 

 Archoiiias {Euterpe) Tereas is common in the forest-paths almost throughout 

 the entire year, while its model, Papilio Nephalion, is, on the other hand, 

 a rare butterfly. Occasionally the relative numbers of different species 

 change very considerably in successive years, and may be entirely reversed 

 in comparatively adjacent districts. Here in Itajahy Colanis Julia is far 

 commoner than the deceptively similar but smaller Eueides AUphera; some 

 months ago, however, to the north of our province on the high land at Sao 

 Bento, I found Eueides AUphera in such numbers that I sometimes caught 

 eight with a single sweep of the net, whilst in the course of a week 1 saw 

 Colcenis Julia but two or three times.* Indeed, it is conceivable that the 

 model species may become extinct while the mimicking species remains 

 unaffected. Thus, according to Mr. Trimen and Mr. A. G. Butler,f Papilio 

 Antimachus and P. Zalmoxis might be imitations of gigantic extinct or 

 still unknown species of Acraa. In the case of the Itiina and Thyridia, 

 under consideration, both species are rare, at least in Santa Catharina, and 

 their relative numbers give no clue, therefore, as to which is the model. 



"The second indication, viz., that the model species bears its own 

 characters, and the mimic acquired ones is found with ease and safety in the 

 fact that the more widely-separated the groups to which the two species belong 

 the further does the imitating species depart from the ordinary characters 

 of its allies. Thus, if certain locusts [Scaphura] are disguised as wasps 

 [Pepsis) — if others [Phylloscyrtus) are disguised as beetles, while others 

 again are disguised as spiders]: — there cannot be the least doul)t, in such 



* [See also Trans. Ent. Soc, 1877, p. 223.— i?. M.] 



+ Eaphael Meldola, " Entomological Notes bearing on Evolution," Ann. Mag. Nat. 

 Hist., Feb. 1858, p. 157. 



I I have never seen this disguise mentioned; I observed it on one occasion. An 

 insect, which I at first took to be a spider, but which nevertheless had a strange 

 appearance, was resting on a leaf; I looked at it on all sides without being clear as 

 to what it was until it jumped up and flew away. The most remarkable feature in 

 it was the long spider-like legs. 



