416 PACKARD— ORIGIN OF MARKINGS OF ORGANISMS. [Dec. 2 



from one locality to another, not further removed than loo to 200 



miles This is remarkable when we consider that the whole 



of the country of the upper Amazons is a nearly level plain, uni- 

 formly covered with forest, and offering no perceptible difference in 

 soil or other physical conditions." Many of these local species have 

 the appearance of being geographical varieties, but they are /'good 

 and true species "; where a number of very closely allied species fly 

 together they keep themselves perfectly distinct, not hybridizing. 

 These species led Bates to believe that '* many of the now distinct 

 species of Heliconidae have arisen from local varieties, segregated 

 from the variations of preexisting widely disseminated species." 

 Corresponding races of counterfeiting butterflies of other families 

 and moths accompany these local forms. ** In some places I found 

 proof that such species are modified from place to place to suit the 

 peculiar forms of Heliconidae there stationed." He then mentions 

 the well-known case of the mimicry of Ithomia by Leptalis. The 

 Ithomiae are all excessively numerous in individuals, while the Lepta- 

 lides are exceedingly rare, and *' cannot be more than as i to 1000 

 with regard to the Ithomiae.' ' In a polymorphic form like the Leptalis 

 lysi?tce, the variations he thinks ''have not arisen by simple varia- 

 tion or sports in one generation, but, as we shall presently see, by 

 an external agency accumulating the modifications of many genera- 

 tions, in two diverging directions." On p. 508 he states that it is 

 " clear that the mutual resemblance in this and other cases cannot 

 be entirely due to similarity of habits or the coincident adaptation 

 of the two analogues to similar physical conditions," yet in the next 

 sentence he remarks : " I think the facts of similar variation in 

 two already nearly allied forms do sometimes show that they have 

 been aff'ected in a similar way by physical conditions," adding that a 

 " great number of insects are modified in one direction by a seaside 

 habitat." " I found also the general colors of many widely differ- 

 ent species affected in a uniform way in the interior of the South 

 American continent. But this does not produce the specific imita- 

 tion of one species by another; // only prepares the way for it^ 

 The italics are ours, and in this pregnant sentence we have the 

 whole matter of mimicry in a nutshell. The physical agents, 

 variations of light and heat, are what prepare the way ; they are 

 the initial causes. 



Bates then asks what advantage the Heliconidae possess to make 

 so flourishing a group, adding : "It is probable they are unpalatable 



