OF THE AMAZON VALLEY. 
507 
Bees, Wasps, and other Hymenopterous and Dipterous insects. The parallelism between 
these several forms and their geographical relations have not yet, I believe, been inves- 
tigated. The resemblances seem to be more closely specific in tropical count riefl than 
in Europe ; and I think it likely that the counterfeits in high latitude s may not ah\ ays be 
found in company with their models. It is possible the geographical relations between 
the species concerned may have been disturbed by the great climatal and geological 
changes which have occurred in this part of the world since the date when they first 
came into existence. 
Not only, however, are Heliconidce the objects selected for imitation; some of them 
are themselves the imitators ; in other words, they counterfeit each other, and this to a 
considerable extent. Species belonging to distinct genera have been confound (id, owing 
to their being almost identical in colours and markings; in fact, many of them can 
scarcely be distinguished except by their generic characters. It is a most strange cir- 
cumstance connected with this family, that its two sections, or subfamilies, hare been 
mingled together by all authors, owing to the very close resemblance of many of their 
species. Analogies between the two subfamilies have been mistaken for affinities. It is 
sometimes difficult to understand in these cases which is the imitator and which the 
imitated. We have, however, generally a sure test in the one set exhibiting a departure 
from the normal style of colouring of their congeners, whilst the other are conformable 
to their generic types. The species of Napeogenea are, by this criterion, evidently all 
imitators of Ithomice; they are also rare insects, like the Leptcdides. The mimetic 
species of Heliconius must be, for the same reason, imitators. 
These imitative resemblances, of which hundreds of instances could be cited, are full 
of interest, and fill us with the greater astonishment the closer we investigate them ; for 
some show a minute and palpably intentional likeness which is perfectly staggering. I 
have found that those features of the portrait are most attended to by nature which pro- 
duce the most effective deception when the insects are seen in nature. The faithfulness 
of the resemblance, in many cases, is not so striking when they are seen in the 
cabinet. Although I had daily practice in insect-collecting for many years, and was 
always on my guard, I was constantly being deceived by them when in the w^oods. It 
may be asked, why are mimetic analogies so numerous and amazingly exact in insects, 
whilst so rare and vague in the higher animals* ? The only answer that I can suggest 
is, that insects have perhaps attained a higher degree of specialization, after their type, 
than most other classes : this seems to be shown by the perfection of their adaptive 
structures and instincts. Their being more numerous and striking in tropical than in 
temperate countries is perhaps attributable to the more active competitive life, and the 
more rapid succession of their generations, in hot than in cold countries. 
It is not difficult to divine the meaning or final cause of these analogies. When we 
* 
nderful as those between Leptalis and 
Mr 
He has observed two species of Oriolida 
normal 
most curiously minute way in colours and in general figure. The associated pairs inhabit separate islands, as follows : 
I. Bourou, Mimeta (Oriolidte) Bouroensis, Tropidorhynchus (Meliphagid*),ii.sp.i I. Ceram, Mimeta Forstim, 
Tropidorhynchus suhcarinatus. 
