202 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Designation of Species 



(1) Original number .... 



(2) Number lost without imitation 



(3) 



(-t) 



Remainders without imitation 

 Number lost with imitation 



(6) 



a > 

 e — 

 (a-e) 



a 

 ^^Fb® 



(i-a+by 



be 

 • • £+b 



B 



b 



= e 



(b-e) 



a-l-b 



Remainders with imitation 



Excess of remainders due 

 to imitation, or "abso- 

 lute advantage" (3) — (5) 



(7) Ratio of excess to remainders 



without imitation (6): (3), 

 :=proportional advantage. 



(8) Ratio of proportional advan- "^ ^ (a— e) 



tage of B to proportional > = ^^^ . 



advantage of A. ^ 



b 1 — 



a + b 



a+b 



a+b 



a — e 



a+b "^ b— e 



a-' 



1— — 



It is evident, then, if e be small compared with a and b, that the 

 proportional advantage of B is to the proportional advantage of A 

 as a-^ is to b^ If, however, the loss (e) is great compared with a or 

 b, the relative gain for the weaker species becomes even greater than 

 the ratio of the squares of b and a. 



If it be true, then, that young bu-ds, when they leave the nest, do 

 not possess a directing instinct telling them what they should and 

 should not eat, but actually do experiment to some extent upon 

 various insects which they meet with, Miiller's law is amply sufficient 

 to account for the numerous cases of mimicry and remarkably close 

 resemblances which are found among the species of the HeUconidae 

 themselves. 



Unfortunately no direct experiments have ever been made upon 

 the feeding-habits of young South American birds, nor have the 

 contents of theu- stomachs been examined. There have been a few 

 experiments, however, which seem to support the idea that some 

 animals do learn to associate an agreeable or disagreeable taste with 

 the coloration and appearance of their prey. It is well knoAvn that 

 Weismann ('82, p. 336-339) found that the black and yellow 

 larvae of Eucheha jacobaeae were refused by the green lizard of 

 Europe. He then introduced some young caterpillars of Lasiocampa 



