Il PROTECTIVE RESEMBLANCES AMONG ANIMALS 59 
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 realised 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 Heli- 
conidz in the form and colouring of the wings. It must 
always be remembered that these two families are as absolutely 
distinguished 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 myself 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 
differences. 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 Heliconide of the district it inhabited ; 
and the results of his observations are embodied in a paper 
published in the Linnean Transactions, in which he first ex- 
plained the phenomena of “mimicry” as the result of natural 
selection, and showed its identity in cause and purpose with 
protective resemblance to vegetable or inorganic forms. 
The imitation of the Heliconide by the Leptalides is 
carried out to a wonderful degree in form as well as in 
colouring. The wings have become elongated to the same 
extent, and the antenne and abdomen have both become 
lengthened, to correspond with the unusual condition in 
which they exist in the former family. In coloration there 
are several types in the different genera of Heliconide. The 
genus Mechanitis is generally of a rich semi-transparent 
brown, banded with black and yellow; Methona is of large 
size, the wings transparent like horn, and with black trans- 
