May 9, 1912] 
collected in all sections of the country and in all | 
seasons of the year. The bearing of these findings 
upon the question of butterflies as food for birds has 
recently been summed up by one of these experts as 
follows :—* Four records of birds eating butterflies are 
all that are afforded by the records of the examination 
of more than 40,000 stomachs in the Biological Sur- 
vey, and one of these probably relates to the capture 
of a very recently emerged specimen, or to one torn 
from the pupa before emergence, as it was accom- 
panied in the stomach by a pupa of the same species. 
This was an Epargyreus tityrus taken by a crow. 
The other records are Eudamus (sp.?) eaten by a 
yellow-billed cuckoo, and two pierid butterflies cap- 
tured by king birds’’ (W. L. McAtee, The Condor, 
January-February, 1912). 
Such a mass of evidence (obtained by most careful 
and painstaking methods from the time the bird is 
shot in its natural habitat until the last recognisable 
portion of the stomach contents is identified and 
tabulated) demonstrates that as a food for North 
American birds butterflies are negligible, so that the 
distastefulness of Anosia plexippus and its close re- 
semblance by Basilarchia archippus appear of no pos- 
NATURE 
sible advantage to these species so far as birds are | 
concerned. Nor can this be lightly pushed aside as 
“negative evidence.’ It shows positively that our 
birds do not eat butterflies to an appreciable extent, 
else immensely more than four butterflies should be 
found in more than 40,000 stomach examinations. 
In a recent article relating to the palatability of 
insects to birds (Proc. Zool. Soc., September, 1911) 
Mr. Pocock explains that the behaviour of birds ex- 
perimented upon in the Zoological Gardens was prob- 
ably due in a measure to “inability in the gardens to 
feed the birds on living insects other than meal 
worms. The living prey was evidently a great treat 
to them, and over and over again I was impressed 
with the persistence shown by birds in persevering 
with insects that were obviously not to their liking, 
returning to the morsels repeatedly as if food of such 
a nature was too good to be wasted.’’ But in the 
first succeeding paragraph he says:—‘‘The insecti- 
vorous birds in our aviaries seemed to know at once 
what the butterflies were; they were on the alert the 
moment one was liberated and pursued it with deter- 
mination and precision, following its every turn and 
twist, and either catching it upon the wing or pounc- 
ing upon it after settling. It is true that this pre- 
datory deftness may have been acquired in relation to 
the chase of insects other than Lepidoptera, but unless 
the birds recognised butterflies in general—a group 
which cannot be mistaken for other insects—as part 
of their natural prey, it is difficult to understand their 
eager excitement at the sight of those I offered 
them.” 
243 
frequent pursuit of butterflies by one another rather 
than from the supposed attacks by birds. 
The pertinency of experiments made under such 
abnormal conditions and the validity of conclusions 
reached from them are open to serious question. 
McAtee (Journ. Econ. Entom., vol. iii., pp. 437-8, 1910) 
has very well shown the futility of basing conclusions 
as to their natural food upon experiments with birds 
removed from their natural environment. He cites a 
number of cases of captive birds which refused specific 
articles of food known to constitute a large part of 
their normal diet, and of others which willingly 
accepted food which they never get in their wild state. 
For examples, a confined blue jay refused acorns and 
beech nuts; a captive bluebird refused one of the 
ground beetles, Scarites subterraneus, and a caged 
song sparrow refused seeds of lamb’s quarter and 
smartweed; yet these birds in a wild state are known 
to take these respective foods in quantity. On the 
| other hand, a captive shrike willingly accepted and 
devoured a goldfish and a black bass, food it probably 
never takes in the wild state. 
Since Mr. Pocock implies that I am one of “the 
dwindling minority of mimicry sceptics,” I should 
like to suggest that before he assumes too much re- 
garding this ‘dwindling minority,’ he make a census 
of the opinions of working zoologists (with reference 
to the usefulness of this particular case of mimicry, 
for example) and learn where the majority actually 
stands and toward which side of the question the 
dwindling really tends. A. M. Banta. 
Cold Spring Harbor, N.Y. 
From Mr. Banta’s concluding paragraph I am 
afraid my reference to the disbelievers in mimicry as 
a dwindling minority hurt his feelings. I hasten, 
therefore, to explain that it was written in a spirit 
of ‘‘chaff,"’ without any intention to give umbrage. 
| Apart from this, there is nothing in my contributions 
As an explanation for the conduct of the birds in | 
Mr. Pocock’s experiments the first quotation above 
seems to me sufficient as regards the avidity with 
which the birds in the gardens pursued butterflies. 
As regards the deftness with which the birds caught 
them, it would seem very remarkable indeed if an 
insectivorous bird normally taking its prey upon the 
wing could not catch insects relatively so slow and 
clumsy on the wing as butterflies. The highly theo- 
retical suggestion that ‘‘birds recognise butterflies as 
part of their natural prey’’ seems to me fanciful, 
entirely unnecessary, and certainly not preferable to 
Mr. Pocock’s first explanation for the eagerness with 
which ail insect food was received by the captive 
birds. 
As to the converse, it would seem more reasonable 
and plausible to attempt to explain the deftness of the 
dodging butterflies as arising from the admittedly | 
NO. 2219, VOL. 89] 
to the question of the distastefulness of Anosia 
plexippus which, in my opinion, needs explanation or 
qualification. The statistics Mr. Banta quotes to 
prove that North American birds do not eat butter- 
flies are full of interest. They show at all events 
that the birds examined had not eaten butterflies 
within a few hours of being shot, and they justify 
the belief that the birds in the areas investigated do 
not trouble themselves to catch butterflies when other 
insects are obtainable. It would be very interesting 
to know if the Department of Agriculture found 
empty stomachs in any birds shot in districts where 
butterflies of various kinds were plentiful and other 
insects scarce. That would be a very important piece 
of evidence in favour of the contention Mr. Banta 
upholds. 
There is perhaps nothing so impressive in connec- 
tion with the theory of mimicry as the vast amount of 
corroborative evidence that has been accumulated since 
it was first propounded. This stands out in strong 
contrast to the complete inadequacy of the explanation 
of the facts on which it is based put forward by its 
opponents. The repetition of this truism is prompted 
by Mr. Banta’s suggestion that the skill butterflies 
display in evading the swoop of insectivorous birds 
has been acquired, not, be it observed, in connection 
with the pursuit of voracious enemies, but in con- 
nection with the apparently often sportive chase of 
one butterfly by another. If we push this argument 
to its logical conclusion, we must also explain the 
vanishing of many butterflies when they alight as the 
result of that same factor. With this view I can only 
sav that I do not agree. R. I. Pocock. 
Zoological Society, April 27. 
