572 Professor E. B. Poulton on- Mr. Thayer s 



improbable, in the case of the groups hitherto explained 

 by the Mlillerian or Batesian theories. Of course close 

 syncryptic resemblances between bark-like moths, lichen- 

 like moths, grass-like and pine-needle-like larvae, etc., 

 have been known and admitted for many years. 



Leaving the tropics we find a beautiful example of 

 mimicry, Batesian, or more probably Mlillerian, which has 

 arisen in Mr. Thayer's own region, and has never wandered 

 much beyond it, an example moreover very well known to 

 the American artist-naturalist, viz. the resemblance of the 

 northern Limcnitis (Basilnrchia) archippus (misijypus) to 

 the Danaine intruder from the tropical south, Anosia 

 pilexipipns. 



In this case there is little doubt that the Nymphaline 

 has been actually drawn away from an ancestral appear- 

 ance, much like that now borne by L. artJicmis, explained 

 by Mr. Thayer as promoting concealment by likeness to 

 flower-masses and their background. If therefore Mr. 

 Thayer is compelled to admit all this effect produced by 

 the Danaine intruder in his own northern region, why 

 should he not be ready to accept far more extended effects 

 of the same kind in the crowded luxuriant life of the 

 tropics ? 



I do not think that naturalists /^rar so entirely misunder- 

 stood the principle of a cryptic pattern resembling some 

 object in the environment combined with the effacive 

 gradation so admirably explained by Mr. Thayer. His 

 illustrations of tiger, lion, brilliantly-coloured fish, appear- 

 ance of forest and shore birds, etc., all these are accepted 

 at once and have been accepted for a long time. But 

 naturalists have regarded the skunk as conspicuous, and I 

 feel sure that Mr. Thayer will admit that it falls into 

 another category from that which includes the forms just 

 named. If concealment is brought about by the beautiful 

 and delicately adjusted effacive gradation from upper dark 

 to under white, as is now generally admitted, surely the 

 " slight amount of effacive gradation " of the black 

 skunk cannot be the same thing, or belong to the same 

 class. 



We must admit Mr. Thayer's main conclusion, that the 

 forms we call conspicuous might be more conspicuous, and 

 also accept the statement that a pattern is less conspicuous 

 than the monochrome. 



Admitting all Mr. Thayer says, at least of the butterflies 



