Article beginning on page 188.
Psyche 5:188-191, 1888.

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188 p.SrCHi%', [April 1889.
genus were reared.
A number of the
in diameter and is supported by the bud
parasite, Orwzyrus minutus, were also
scales of Q. bicolor and 2. macro-
reared. carpa. Galls taken April 29 gave flies Neuroterus vesicula Bass. When May 3.
the larva of this species is full grown Neither guests nor parasite were the gall is a thin shell, globular in form, reared.
almost black in color, covered with (To be continued.) light spots, does not exceed three mm.
NOTES ON THE PARASITE OF THE SPOTTED LADY-BEETLE (MEGILLA MACULA7L4).l
BY CLARENCE MOORES WEED AND CHARLES A. HART. Our attention was first called to this
subject during the summer of 1884 when
dead examples of the common spotted
lady-beetle (MegiZZa maculata) were
found by Mr. Hart on various plants,
each having beneath or beside it a com-
pact brown cocoon, about 4 mm. long
by 2 mm. wide. The matter was not
especially studied at that time, and no
further attention was paid to it until 17 July 1885, when several examples of
the same kind were found in a corn-
field. The lady-beetles were in two
cases dead, while in three or four others 'The present paper is mainly an abridgement of a more elaborate one prepared for the Cleveland (1888) meeting of the Entomological club of the American association for the advancement of science (the title of which was sent to the secretary) but as I was unable to reach Cleveland before the club adjourned it was not read. Since the meeting, however, an article cover- ing the main grounds of our paper has been published in Insect lift (Oct. 1888, v. I, p, 101-iq) by Dr. Kiley, but it has been thought worth while to present these additional observations upon the presence and habits of the parasite and its host in Illinois, where all the obser. vations here recorded were made, as a part of the work of the Illinois State laboratory of natural history. C:M. W.
they were alive and embracing the co-
coon with their legs. One of the
cocoons attached to a dead beetle had a
cap removed from one end, the parasite
having doubtless escaped through the
opening thus made. The other cocoons
were placed in a breeding cage, and the
images were bred from them.
A living specimen of the same lady-
beetle was again found 5 August 1885
on corn, at the base of a leaf, with a co- coon of its parasite entangled in its legs. It was retained alive for examination
and acted much as a spider does about
its egg-sack. When found, its hind
claws were caught in the loose silk of
the cocoon, but when the cocoon was
removed the lady-beetle seemed greatly
disturbed, and would fold its legs about anything within reach. It walked hold-
ing its body high in the air, and when it came in the vicinity of the cocoon, its
claws would become entangled so that it
dragged the cocoon along after it. When
placed upon its back it waved its feet




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April 1889.1 .P~^~THJ?~. 189
excitedly as most insects do when in this position; but as soon as the cocoon was
placed within reach, it folded its legs
about it and became quiet, remaining so
although still lying on its back.
Early in May 1886, another Megilla
was found over a cocoon on a clover
leaf, and was transferred to a breeding
cage. When next exan~ined, 26 May,
the parasite had emerged and the beetle
was dead, although still entangled in
the cocoon.
Again 18 May 1886 another Megilla
was found on a currant leaf clinging to a cocoon like those above mentioned. It
strongly resisted efforts to dislodge it, and refused to walk when removed -
clinging to the leaf-stem or other small object as it had done to the cocoon. No
sign of external injury could be seen.
When put in alcohol the beetle refused
to let go the cocoon until dying.
Thfe same kind of beetle and cocoon
were again found by a member of the
Natural history society of the University of Illinois at a field-meeting in May
1887, in the woods near Mahomet, in
central Illinois, and was shown to most
of the members present. The Meg'illa
was alive and clung to the cocoon with
great, pertinacity.
The accompanying illustration, drawn
by Miss Lillie Hart, shows the beetle
over the cocoon, on a clover leaf.
The parasite bred by us agrees with
the figure given by Dr. Riley of the
species bred by him from this coccinellid, for which he has proposed the provis-
ional name Centisfes americana. He
had obtained only female specimens,
however, while both sexes are repre-
sented in the Laboratory collection. The two sexes may be described as follows :
Length, 2.5 mm. 8 9 . Black, some-
what shining, covered with rather long
brown hairs ; head with pal pi and man-
dibles yellowish brown ; black on vertex surrounding ocelli. Abdomen, except
tergum of first segment, shining, dark
brown.
Antennae as long as body, pi-
ceous except at base where they are
tawny olive. Mesonotum coarsely punc-
tate, with subtriangular areas a4acent
to the insertion of the wings more shin- ing and with fewer punctures ; these
areas sometimes brownish. Metanotum
coarsely reticulate. Tergum of first ab- dominal segment longitudinally rugosely
reticulate, remaining segments smooth
and shining.
Legs of 9 dark yellowish




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1%) ps X'HE. [April 18%.
brown, with coxae blackish, and tarsi
together with intermediate and posterior femora, obfuscate. Legs of J* lighter col- ored, with coxae unicoloro~~s with legs ; posterior tibiae at tip, and posterior tarsi dusky. Tegtilae piceous. Wings sub-
hyaline ; veins and stigma deep brown.
Ovipositor nearly as long as abdomen ;
sheaths piceous.
Described from four specimens (3 Q ,
I <? ) bred from cocoons found in con-
nection with MegiZZa maculata.
The cocoon is of a clear reddish
brown color, 4 mm. long by 3 mm.
wide. Its texture is compact, except
that there is considerable loose silk on the outside.
COSMOPOLITAN BUTTERFLIES.
BY SAMUEL HUBBARD SCUDDER, CAMBRIDGE, MASS. Strictly speaking, there is no such
thing as a cosmopolitan butterfly ; yet
there is one species, Vanessa cardu<
which may well merit that name, since
it is found in every quarter of the globe , with the exception of the arctic regions, a part of South America and most of the
West India islands ; there are also other butterflies whose recent extension natu- rally leads to the inquiry, What should
prevent their spreading over the entire
globe, 01- what are the elements that
enable a butterfly to gain and maintain
a foothold in so many diverse regions.
Let us look for a moment at the
peculiarities of distribution of this nearly cosmopolitan butterfly. It belongs to a
subdivision of the genus Vanessa, the
members of which (with the sole excep-
tion of this cosmopolitan species) are
found exclusively in the New World ;
while the antithetical section (with the single exception again of one member
found both in Europe and the United
States) is exclusively confined to the
Old World. Judging from this fact we
may venture to assert with considerable
confidence that this cosmopolitan butter- fly originated in America. Yet it is
just on. fbi's continent that its distri- button is most Ii~nited! It is known in
only a comparatively small portion of
South America and occurs on none of
the West India islands, with the excep-
tion of Cuba, where it is rare. The
cause of this limitation cannot be attri- buted to the food plant of the cater-
pillar ; for the thistles upon which it
lives are quite as abundant in these
regions as in many others which it has
invaded, certainly sufficiently abundant for all its uses.
Nor can the heat of the
tropics be placed as a difficulty in the way, since there is no place where it
flourishes more abundantly than in the
tropics and subtropics of the Old World, repeated invasions of Europe by hordes
from the south where they had out-
grown their opportunities being already
on record.
Assuming, then, America to have
been its original home, it would seem




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April 1889.1 PS2Tkm. 191
as if we might fairly conclude that a
butterfly of a dominant type, after its
distribution in the region of its birth
had reached its limits (the balance be-
tween the competitors in the struggle
for existence being fairly struck), on
being introduced into a new world,
where it had to contend in the struggle
for supremacy with none of the mem-
bers of its own restricted group, which
had stood in its way in its native home, would suddenly find that it had reached
a region ready for conquest and would
spread therein with such success as to
completely overrun that division of the
world.
That this is a probable picture of
events which actually transpired in this instance, the result of which we see to- day, is rendered more probable by other
events which have taken place under our
very eyes, which, though not strictly
parallel, seem to have a lesson. Pieris
r@ae, originating in the Old World
among a circle of relatives far greater
than exists in North America, relatives
whose natural food plant is precisely its own, has been suddenly transported to
America, where the group to which it
belongs is much more poorly repre-
sented in species, all feeding upon plants of the same family ; and though there
are among them species of the genera
Pontia and Pieris having intimate rela-
tionship with forms which have more or
less successfully contended with *ae
in their own home, the inexperience of
the American species with such a rude
antagonist has made them no match for
it; so that in the mere quarter of a cen- tury since its introduction it has spread over half the territory of the United
States, doing now vastly more
injury
than all the others of its own tribe com- bined and contending with them so suc-
cessfully that their scarcity where for- merly abundant is everywhere noticed.
In this latter instance commercial agen- cies are amply sufficient to explain the introduction of this butterfly into our
country. It is, however, an insect de-
pendant upon a group of food plants
which forbid its passage into the tropics and so will prevent its spread over more than the north temperate zone.
It is plain that no butterfly can become cosmopolitan whose caterpillar does not
feed upon plants found in all quarters of the globe. Yet this is plainly not a
sufficient cause for distribution. As a
proof of this it may be pointed out that one of the most polyphagous of our
butterflies, Jasoniades glaucus, which
has an unusually extended distribution in. North America, where it has several
allies, has never become cosmopolitan ;
while plants to which it might easily adapt itself are found in every quarter of the globe. Moreover, the alliances of the
genus are wholly with tropical American
forms and its ancestors unquestionably
originated in that part of the world ; yet the genus is not found in the tropics.
Nor has it ever spread to the Old World ; at the same time there are other genera
of the same tribe, not distantly related, which do possess members in both the
New and Old Worlds, whose food is of
a much more restricted range ; such are
the genera I$hicZides and Papilio.
We have another instance of possible
cosmopolitanism which is perhaps more




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