76 MR. H. W. BATES ON THE INSECT FAUNA 
is some cause to believe that they are unpalatable to insectivorous 
animals—at least the Acreoid group. This would not explain, 
however, the numerous mutual resemblances of the Heliconine. 
All that we can say is, that some species are more successful in the 
battle of life than others, and that it is an advantage to others 
not otherwise provided for if they are brought to be deceptively 
similar to them. The process by which this is brought about in 
nature is a problem involved in the wider one of the origin of all 
species and all adaptations. There are some curious facts, however, 
in the geographical distribution of the species and varieties of 
certain members of the genus Leptalis which throw great light 
on the subject, at least as far as the Leptalides are concerned, 
which offer perhaps the most remarkable cases of mimicry. It 
would appear by these faets that a mimetic species has not always 
existed under the same specific mimetic dress which it now wears, 
as the following example shows. Leptalis Lysinoé in one district 
is very variable, but none of its varieties mimics very closely a 
Heliconine species there residing; they rather tend to imitate 
species of Stalactis—another flourishing group belonging to a 
different family ; but a few individuals occur intermediate in cha- 
racter, and quite uncertain in their analogies. In another district, 
again, this species is very variable, and some of the varieties ‘are 
indeterminate in their analogies, but the greater number resemble 
to deception one or other of three species of Ithomia, amongst 
which only they are found, and from which they are quite undi- 
stinguishable, except when closely examined in the hand. Ina third 
locality this Leptalis is found under one form only, distinct from 
any of the varieties occurring elsewhere, but mimicking closely an 
Ithomia also found there and not in the other two districts. Thus 
we see that, although the changes a species undergoes, first simply 
variable, and then presenting local varieties closely mimicking 
other forms, cannot be watched in nature as they take place suc- 
cessively, they can be seen as it were simultaneously by tracing 
them over the area of its distribution. Leptalis Lysinoé is a 
species of great rarity, and therefore liable to complete extinction. 
It seems fair to conclude that, as the [thomie which it mimics are 
certainly spared by the swarms of insectivorous birds which daily 
sweep through their abodes, the Leptalis, not being so favoured, 
escapes destruction by wearing the livery of the Ithomie. It may 
be added that the family to which Leptalis belongs (Pieride) are 
certainly much persecuted by insectivorous animals. As, then, the 
Leptalis varies from one locality to another, some few of its varia- 
