ni Lia 
tative species, inhabit different areas of the same continent, the 
members of these mimetic groups all change their aspect together, 
and in the same direction. By the kindness of Professor POULTON, 
I am enabled to illustrate this statement by a very beautiful series 
of Butterflies from Central and South America. The assemblage in 
question contains species of very diverse affinities, including Itho- 
miines, Heliconiines, Danaines, Nymphalines and the females of 
certain Pierines, all characterised by a peculiar arrangement of the 
colours red, yellow and black. While these figures are being shown 
on the screen, I quote from a former description of my own 
« The members of this assemblage as it occurs in the northern 
part of Central America — Guatemala to Nicaragua — present in 
common a remarkable streakiness of pattern, a feature that makes 
them easily recognisable among the corresponding forms from 
other regions of the same continent. Passing on to Venezuela, we 
find among the geographical races, or, if we like to call them so, 
the representative species, that there replace the Central American 
forms, a tendency to the breaking-up of the streaks, and a slight 
encroachment of the red ground-colour upon the yellow of the 
apex. In Trinidad there occurs a general paling of the ground- 
colour, due to an increase of yellow pigmentation, and running, 
as before, through the entire group. Next, taking the correspond- 
ing Guiana forms, we find a further breaking-up of the streaks 
into spots, and also a general darkening, especially of,the hind- 
wings, which gives a most characteristic aspect to the whole 
assemblage. In Fast Brazil we have a modification which some- 
what recalls the Trinidad facies, though here the yellow streak 
on the hindwing is better defined, and a pale spot makes its 
appearance on the apex, the dark area of which is less broken up. 
At Ega, on the Upper Amazon, a curious dark chestnut tinge 
pervades the group, while in Peru a characteristic spottiness takes 
the place of the streaky pattern we saw elsewhere, and the apex 
becomes more uniformly dark. Finally, in Ecuador the streaks 
have all but disappeared, and even the spots have become almost 
blocked out by a dark infusion which now occupies, not only the 
apex, but also a large part of the base of the forewing, and the 
whole, or nearly so, of the hindwing. After a little study of some 
of the typical members of each of these geographical groups, it 
becomes easy to pronounce, with a considerable degree of confi- 
dence, upon the local habitation of a species that we may never 
have met with before. » 
There are two genera of African Pierines, Mylothris and Phris- 
