The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1867-08-22

| would be easily distinguished ana uo.Vt -,
yet at longer distance 1t might % 90, a.,
for one of the uneatable group ana SO De
| nassed Inv and gain another days lie, Whloh
| mioht in many cases be sufficient ior II 10 lay
a dSgantitv of eggs and leave numerous pro-
oe1v MANY of which would inherit the pecu-
fiaTity which had been the safeguard OF their
paSemS Now this Hypothetical case is exactly
realized in South America Among the
white butterflies forming the family Pieride
| (many of which do not greatly differ in APP
pearance from our own cabbage butterfies)
is a genus of rather small size (Leptalis);
some species of which are white like their
allies, while the larger number exactly re-
semble the Heliconida in the form and color
ing of the wings. 1t must be always re-
membered that these two families are as absO-
lutely distinguished from each other by struc-
tural characters as are the oarnivora and the
ruminants among quadrupeds, and that an en-
tomOlOgist can always distinguish the one
from the other by the structure of the feet just
as certainly as a zoologist can tell bear from
a buffalo 10y 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 Mr.. Wallace
were many times deceived at the time of cap
ture, and did not discover the distinctness of
the two insects till a closer examination de-
tected their essential differences. During his
residence of eleven years in the Amazon Val
ley, 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 Heliconi-
d@ of the district it inhabited and the results
of his observations are embodied in the paper
published in the Linn8an Transactions y in
which he first explained the phenomena
of 'mimicry" as the result of natural selec-
tion, and showed its identity in cause and
purpose with protective resemblance to vege-
table or inorganic forms.
The imitation of the Heliconid9 by the
Leptalides is carried out to a wonderful
degree in form as well as in coloring. The
wings have become elongated to the same
extent, and the antenn9 and abdomen have
both become heightened, to correspond
with the usual condition in which they
exist in the former family. In coloration
there are several types in the different
genera of Heliconide. The genus Mecha-
nitis is generally of a rich semi-transparent
brown, banded with black and yellow
Methona is of large size, the wings trans
parent like horn, and with black transverse
bands; while the delicate IthOmias are all
more or less transparent, with black veins
and borders, and often with marginal and
transverse bands of orange red. These
different forms are all covered by the various
species of Leptalis, every band and spot
and tint of color, and the various degrees
of transparency, being exactly reproduced.
As if to derive all the benefit possible from
this protective mimicry, the habits have be-
come so modified that the Leptalides gene
rally frequent the very same spots as their
models, and have the same mode of flight;
and as they are always very scarce (Mr.
Bates estimating their numbers at about
one to thousand of the group they re.
semble), there is hardly possibility of their
being found out by their enemies. 1t
is also very remarkable that in almost
every case the particular Ithomias and other
species of Heliconid@ which they resemble,
are noted as being very common species,
swarming in individuals, and found over
wide range OF country. This indicates anti
| quity and permanence in the species, and is
exactly the condition most essential both to
aid in the development and to increase the
utility of the resemblance.
But the Leptalides are not the only group
who have prolonged their existence by imi-
tating the great protected group of Heliconida;
a genus of quite another family of most lovely
small American butterflies, the Erycinide,
and three genera of diurnal moths, also pre-
sent species which often mimic the same domi-
nant forms, so that some, as Ithomia ilerdina
of st. PaulO, for instance, have flying with
them few individuals of three totally diffe-
rent insects, which are yet disguised with ex-
actly the same form, color, and markings, so
that all four are undistinguishable when on
the wing. Again, the Heliconide are not the
only group that are initiated, although they
are the most frequent modes.
In other parts of the world an exactly
parallel series of facts have been observed.
The Danaide and the Acraide of the Old
World tropics form, in fact, one great group
with the Heliconde. They have the same
general form, structure, and habits they pos
sess the same protective odor, and are equally
abundant in individuals, although not so
varied in color, blue and white spots on black
ground being the most general pattern. The
insects which mimic these are chiefly Papilios
and Diademe, genus allied to our peacock
and tortoise-shell butterflies.
Passing on to India, we have Danais tytia,
butterfly with semi-transparent blush wings
and border of rich, reddish brown. This re-
markable style of coloring is exactly repro
duced in Papilio agestor and in Diadema mama,
and all three insects not unfrequently come
together in collections made at Darieeling.
In the Philippine Islands the large and curious
Idea leuconoe, with its semi-transparent white
wings, veined and spotted with black, is copied
by the rare Papilio ideodes from the same
islands.
In the Malay archipelago the very common
and beautiful Eupl@a midamus is so exactly
mimicked by two rare Papilios (P. paradoxa
and p. enigma) that Mr.. Wallace generally
caught them under the impression that they
were the more common species; and the equally
common and even more beautiful Euplea rha-
damanthus, with its pure white bands and
spots on ground of glossy blue and black, is
reproduced in the Papilio caunus. Here also
there are species Of Diadema, initiating the
same group in two or three instances; but we
shall have n adduaa fhoca f,1r m in