82 MIMICRY, AND OTHER PROTECTIVE 
ata longer distance it might be mistaken for one of the 
uneatable group, and so be passed by and gain another 
day’s life, which might in many cases be sufficient 
for it to lay a quantity of eggs and leave a numerous 
progeny, many of which would inherit the peculiarity 
which had been the safeguard of their parent. 
Now, this hypothetical case is exactly realized in 
‘South America. Among the white butterflies forming 
the family Pieride (many of which do not greatly 
differ in appearance from our own cabbage butterflies) 
is a genus of rather small size (Leptalis), some species 
of which are white like their allies, while the larger 
number exactly resemble the Heliconide in the form 
and colouring of the wings. It must always be re- 
membered that these two families are as absolutely dis- 
tinguished from each other by. structural characters as 
are the carnivora and the ruminants among quadrupeds, 
and that an entomologist can always distinguish the one 
from the other by the structure of the feet, just as 
certainly as a zoologist can tell a bear from a buffalo 
by the skull or by a tooth. Yet the resemblance of a 
species.of the one family to another species in the other 
family was often so great, that both Mr. Bates and my- 
self were many times deceived at the time of capture, 
and did not discover the distinctness of the two insects 
till a closer examination detected their essential differ- 
ences. During his residence of eleven years in the 
Amazon valley, Mr. Bates found a number of species 
or varieties of Leptalis, each of which was a more or 
less exact copy of one of the Heliconidz of the district 
