ILLUSTRATIVE OF NATURAL SELECTION, 155 
many analogous cases occur; and as the whole 
history of many of these has been investigated by 
breeding successive generations from the egg, it is 
to be hoped that some of our British Lepidopterists 
will give us a connected account of all the abnormal 
phenomena which they present. Among the Coleop- 
tera Mr. Pascoe has pointed out the existence of two 
forms of the male sex in seven species of the two 
genera Xenocerus and Mecocerus belonging to the 
family Anthribide, (Proc. Ent. Soc. Lond., 1862); 
and no less than six European Water-beetles, of the 
genus Dytiscus, have females of two forms, the most 
common having the elytra deeply sulcate, the rarer 
smooth as in the males. The three, and sometimes 
four or more, forms under which many Hymenop- 
terous insects (especially Ants) occur, must be con- 
sidered as a related phenomenon, though here each 
form is specialized to a distinct function in the 
economy of the species. Among the higher animals, 
albinoism and melanism may, as I have already stated, 
be considered as analogous facts; and I met with 
one case of a bird, a species of Lory (Hos fuscata), 
clearly existing under two differently coloured forms, 
since I obtained both sexes of each from a single 
flock, while no intermediate specimens have yet been 
found. 
The fact of the two sexes of one species differing 
very considerably is so common, that it attracted but 
little attention till Mr. Darwin showed how it could 
in many cases be explained by the principle cf 
