on the Red-breasted • Starlings, etc.



153



birds, and oddly enough they are exactly copied, not only in the

colouring of both surfaces, but in some of their habits by the

species of the genus Leistes (Marsh-Troupials). So close is the

resemblance between Leistes snperciliaris and Trupialis deplibpii ,

that, if it were not for the shorter broader finch-like beak of the

former, it might almost be mistaken for the Military Starling.

Both birds crouch in the same manner when alarmed, and fly

recklessly and irregularly upwards, singing their fearful song,

when courting.


Now what has often puzzled me is to discover what possible

advantage the Red-breasted Marsh Troupial can gain by its

resemblance to Defillipi’s Starling: I can discover none what¬

ever. Moreover, if there be an advantage and we assume that

Leistes guianensis, in like manner, formerly copied the colouring

of Trupialis bellicosa ; why is it that these two birds now inhabit

different regions ? Is not this of itself a proof that they can get

along perfectly well independently of each other? If so, why

are the species of Leistes so like the species of Trupialis ? It is

not only in birds that cases of this kind occur ; for, among butter¬

flies also, whole series of related genera can be arranged in

parallel rows of species each resembling the other in colouring;

none of them apparently needing to resemble the others, because

all are alike noxious and distasteful to insectivorous animals.*


It has been suggested that the resemblance of many genera

to each other impresses their objectionable character more forcibly

upon their enemies, and thus they are less liable to be maimed by

young and inexperienced creatures seizing them ; that one suffers

for the many, and so the latter escape unharmed : a view which

has always seemed to me far-fetched and improbable, when one

observes the exactness with which all the patterns in a genus are

repeated in half a dozen others, as well as in other unrelated,

palatable, and palpably mimicking genera.


Surely it is more reasonable to suppose that colouring is

developed in certain fixed directions and that, when not injurious

to an animal, it may be retained long after the structure has

been modified ; and the tendency to variation in the same lines

may, in like manner, be retained.



The Ithomimcc.



