Andrew P. (Andrew Preston) Peabody.

The American entomologist: online

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as at Rochester to have spread therefrom as from
a focus. Unless our memory greatly deceives
us, Mr. Geo. Brackett, of Maine, described this
same insect many years ago, as existing in that
State, though he gave it a different specific name,
and was not at all aware that it had been intro-
duced from the other side of the Atlantic. We
also heard of it in the summer of 1867, from Mr.
A. H. Mills, of Vermont, as being very desti*nc-
tive in his neighborhood. Not improbably, it
was independently imported at other points in
the East. Wherever it is introduced it spreads
with great rapidity, and as there are two broods
every year, it soon multiplies so as to strip all
the currant and gooseben^ bushes bare and
utterly ruin the crop, besides eventually destroy-
ing the bushes, unless proper measures be taken
to counteract it. Throughout the western parts
of New York, as we have been informed by our
ornithological friend Dr. Velie, the cultivation
of entrants and gooseberries has been almost
entirely given up, on account of the depreda-
tions of this seemingly insignificant little sav-
age. And, according to Dr. Fitch, at Water-
town, N. Y., " it kept the bushes so destitute
of leaves in most of the gardens, that in three
yeai*8 they were nearly or quite dead."

The Imported Currant-worm Fly (Fig. 7, a
male, b female, both enlarged), belongs to the
Sawflies {Tenthredo Family) — a group of the
Order of Clear-winged Flies {Hymenoptera) ^
which is remarkable for having most of its larva?
with the same plant-feeding propensities as those
of the gi'eat bulk of the larvae of the Moths, and
witli very much their general appearance. Saw-
fly larvae, however, may be readily distinguished
fi'om moth larvae, in the majority of cases, by
having either 22, 20 or 18 legs; whereas the
greatest number of legs that any moth larva has
is 16. The species that we now have to do with



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THE AMERICAN ENTOMOLOGIST.



comes out of the ground soon after the leaves
of the currant and gooseberry bushes, upon
which it feeds, put forth in the spring, or from

[Fig. 7.]



h



Colore— Black and yellow.

the latter part of April to the forepart of May.
The sexes then couple, and the female proceeds
to lay her eggs along the principal veins on the
under side of the leaf. From these eggs shortly
afterwards hatch out minute green 20-legged
larvffi or worms, which at first have black heads
and many black dots on their bodies, but after
moulting for the last time are entirely of a grass-
green color, except the large dark eye spots on
each side of the head found in all larvae belong-
ing to this genus, and except that the joint next
the head and the two hindmost joints are of a yel-
low color, as is also the case in the less mature
larva, which bears so many black markings. In
the annexed Figure 8, a, a, a, a shows larvae of
different sizes in different positions : and b gives

[Fig. 8]



Colors— Green, yellow and black.

an enlarged view of one of the abdominal joints
in profile, so as to exhibit the position of Uio



black spots. AVhen full-grown the laiTse are

about three-quarters of an inch long, and from

their greatly increased size, make their presence

readily known by the sudden disappearance of

! the leaves from the infested bushes. Shortly

afterwards, having attained a length of fully

I three-quarters of an inch, they burrow under-

: ground, generally beneath the infested bushes,

or, if there are many leaves lying on the ground,

I simply hide under those leaves. In either case

I they spin around themselves a thin oval cocoon

1 of brown silk, within which they assume the

pupa state. But frequently, as we are assui^ed by

Mr. Saunders of Canada West, and as European

observers have noticed, they spin their cocoons

in the open air upon the bushes. About the

last week in June or the first part of July, or

occasionally not until the beginning of August,

the winged insect burets forth from the cocoon

and emerges to the light of day ; when the same

process of coupling and laying eggs is repeated.

The larvae hatch out from tliis second laying of

eggs as before, feed on the leaves as before, and

spin their cocoons as befoi'e; but the perfect fly

from this second brood does not come out of the

cocoon till the following spring, when the same

old series of phenomena is repeated.

From the drawings of the Male and Female
Fly given above (Fig. 7), the reader will sec
at once that the fwo sexes differ very widely.
This is very generally the case among the Saw-
flies, and it is a remarkable and most suggestive
fact that, when this takes place, the body of the
male is almost invariably darker than that of
the female. Nor does our species, as will be
observed at the first glance, form any exception
to the rule. Indeed, as with two other Sawflies
that devour the foliage of our Pines and Firs
{Lophyrus Abbot tii and L» abietis), the body of
the male is almost entirely black and that of the
female almost entirely yellow ; so that at fii'st
sight we should suppose the two to belong to
different species. Since, from some unaccount-
able oversight, Dr. Fitch has overlooked this
fact, and described both sexes as being colored
in the manner which is exclusively to be met
with in the female, it will be as well to add here
full descriptions, first of the female fly and
secondly of the male fly. These descriptions
were, indeed, published by the Senior Editor
two years before Dr. Fitch's appeared ; but the
writings of that gentleman circulate so exten-
sively that, when he makes an important mistake
such as this, it is proper that it should be cor-
rected in our columns in detail.

FK»f ALE Fly.— General color of body bright honey -
yellow. Head black, with all tlie parts between and
below the origin of the antennae, except the tip of the



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THE AMERICAN ENTOMOLOGIST.



17



mandibles , dull honey-yellow. Antennas brown- black ,
often tinned with rufous above, cxctpt towards the
base, and beneath entirely dull nifous except the two
basal joints; four-tittht^ as louj? as the body, joint .'I,
when viewed luteruUy, four times as long as wide,
joints 3-5 equal in U-nj^h, 0-9 very slowly shorter and
ishorter. In two females the antennae arc l()-jointed,
joint 10 slender and % as lonj? as D. y/<'/r/r with the
anterior lobe above, a wide stiipe on the disk of each
lateral lobe which is very rarely reduced to a mere dot,
or ver>' rarely the whole of each lateral lobe, a spot at
the base and' at the tip of the scutel, the two spots
sometimes confluent and very rarely subobsolete, a
small spot at the outer end of eacli ccnchrus and a
geminate small spot transversely arranj^cd between the
cenchri, the tip of the metathoracic scutel, the trout
and hind ed«;e above of what scenes the Ist abdominal
joint, but is in reality the hind part of the metathorax,
or verv rarely iti whole surface above, and also the
whole lower surface of the breast between the front and
middle legs, or very rarely two largo spots arranged
crossways on that surface, all black . Cenchri whitish.
A^doihen with joints 1 an<I 2 very rarely ctlged at tip
with black. 8heath.s of the ovipo.sitor tipped more or
less with black, the surrounding parts sometimes more
or less tinged with dusky. The triangular membrane
at the base of the abdomen alcove, whiti>h. /^<?« bright
boney-yellow"^ all the coxaj and trochanters whitish;
the extreme tip of the hind shanks and the whole of the
hind tarsi, brown-black. Winrtt gla»sy; veins and
8tigma brown-black, the latter as well as the eosta
obscurely marked with dull honey -yellow. In a single
$ all three Kubmarginal ero>s-veln*s are absent in one
wing, and only the basal one is present in the other
wing. In another $ all three are in<ii>tinctly present
in one wing, and in the other only the l)asal one and a
rudiment of the terminal one. In a single wing of two
other $ , the terminal submarginal cro>s-vcin is absent.
And in a single $ there are but three submarginal cells
in cither wing, precisely as in the genus //«?//</.— Length
$ 0.22— 0.-28 inch. Front wing $ 27— 0.:^^ inch.
Kxpanite of wings $ 0.53 — 0.C4 inch, (wings depressed).
Malk Fly.— (leneral color of bo«ly black. Head
with the clypcus and the entire mouth*, except the tip
of the mandibles, dull honey-yellow. Antenna? brown-
black, often more or less 'tinged with rufous beneath
except towards the base: as long as the body, the joints
proi)ortioned as in $ , l»ut the whole antenna, as usual
m this sex. vertically much more dilated, so that joint
3 is only 2^ ^ times as long as wide when viewed in pro-
tile, thoriir with the wfng-scalcs and the entire collare
honey-yellow. Cenchri ulntish. Ahdoihen with more
or less of its sides, the extreme tii> above, audits entire
inferior suriaee honey-yellow. Lftjs as in $ . UV/jj/*
as in $ . In two (J the middle submar;;inal cross- vein
is absent in both wings, so that if captured at large
they would naturally be referred to the genus Euura.
In two other (^ this is the case in one wing only. An-
other <^ has but the basal submarginal cros^-vein
remaining in each wing. And in two oilier -^^ the ter-
minal submarginal ero.ss-vein is absent in one wing —
Length (^ 0.20— 22 inch. Front wing ^ 0.2.1-0.25
inch. Expanse of wings (^ 0.44— o 51 iiich, (wings
depressed.)

Desci-ibed from 22 ^ and U\ ^ , 3 (5" and i ?
of the spring brood. The fact of two ? , con-
tiiiry to the established charucter of the genus
^ematus, having lO-jointed instead of D-jointed
antennae is a variation of a kind of which no
other exanaple in the whole Family of Sawflies
is on record. Had such a specimen been cap-
tured at large, instead of being bred, along with
a lot of normal $ , from the same lot of larvae
taken from the same lot of bushes, it would pro-
bably have been made the basis for a new genus
and a new species by some of our genus-grinding
closet-entomologists.

The mode in which this Currant Worm has



been transmitted, first from the European nur-
sery to the American nureery, and afterwards
all over several States of the Union, can be
easily explained. As has been stated just now,
it usually passes the autumn and winter in the
ground under the bushes, where it has fed,
housed in a little oval cocoon IVom i to I inch
long. Hence if, as often happens, infested
bushes are taken up in the autumn or early in
the spring, with a little dirt adhering to their
roots, and sent off to a distance, that dirt will
likely enough inclose a cocoon or two. A single
pair of cocoons, if they happen to contain indi-
viduals of opposite sexes, will be sufiicient to
start a new colony. The first and probably the
second year the larvas will not be noticed; but
increasing, as almost all insects do, unless
checked ft-om some extraneous source, in a fear-
fully rapid geometric progression, by the third
or fourth year they will swarm, strip the bushes
completely bare of their leaves, and ruin the
prospect for a good crop of fruit. Of course,
like other winged insects, they can fly fi*om
garden to garden in search of a suitable spot
whereon to deposit their eggs ; so that any point
where they have been once imported becomes,
in a few years, a new centi-e of distribution for
the immediate neighborhood.

Nurserymen and all others, importing Goose-
berry and Currant bushes from a distance, should
be particularly careftil, before they plant them,
to wash tlie roots thoroughly in a tub of watery
and burn or scald whatever comes off them.
Any cocoons, that may happen to be hidden
among the dirt attached to the roots, will then
be destroyed. By attending to this precaution
the dissemination of this mischievous little pest,
throughout the United States, may be greatly
retarded for many years to come.

For those who are already cursed with it, the
same hellebore whicli we shall recommend at the
end oftliisArticle, as universally efficient against
all three kinds of Gooseberiy and Currant
Worms, ig the best, the cheapest and the most
available remedy. Where this cannot be con-
veniently obtained, the Imported CuiTant Worm,
owing to a peculiarity in its habits, can be pretty
successfully fought upon a system, which is inap-
plicable to the other two species on account of
the difference in their habits. Unlike the other
two, the Imported Currant Worm, as has been
already stated, lays its eggs in large groups on
the under side of the leaf, and upon the princi-
pal veins, as shown at No. 1 in Figure 9, instead
of attaching them in comparatively small patches
to the twigs and branches. Hence, when the
eggs hatch out, the minute little larvas can find



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THE AMERICAN ENTOMOLOGIST.



[Fig. 9.1



plenty of food without wandering off, and they
have the habit when very young of boring 8raall
holes through the leaf as shown at No. 2 in Fig-
ure 9, and when they become a little older,
holes that are a little larger as shown at No. 3.
It is evident that such holes as these may be
readily recognized, and the leaf be carried larvae
and all far away from any currant or gooseberry
bushes and left to wither there, or — to make
assurance doubly sure — thrown into the fire.
If, however, the young larvae are removed a few
rods away from any plant belonging to the
botanical genus Eibes ( Currant and Goose-
berry), they will be sure to die of starvation.
For they cannot feed on anything else, any more
than the common Locust-borer can live on an
Apple-tree. As the eggs are laid in such large
groups, there will be but a few leaves bearing
these newly hatched larvae to remove from every
bush.

Wherever this Currant Worm has been in-
troduced, there has prevailed from some cause
or other a popular superstition, that the currants
grown upon the infested bushes are poisonous.
This is a mere delusion. They may be, and
very probably are, unwholesome, just as any
other fruit would be perhaps more or less
unwholesome, if grown under such unnatural
conditions as to seriously affect the health of
the tree; but we have the authority of Dr.
Fitch, himself a physician, for believing that
the common notion on this subject is entirely
erroneous.

Entomologists have often speculated, whether
the same parasite will attack several distinct
species of insects, and whether any European
species, which has been introduced into America
without its peculiar parasites, will ever be
attacked by the indigenous parasites of this
country. So far as regards our Imported Cur-
rant Worm, both these questions can be an-



swered in the affirmative. Three years ago the
Senior Editor published the fact, that this worm
was parasitically infested by the larva of a small
Ichneumon-fly ( Brachypteims , micropterusy
Say), which has such short and rudimentary
wings, that it has very much the appearance
of an Ant; and more recently it has been dis-
covered by that excellent observer, J. A. Lintner
of Schoharie, N. Y., that the eggs of this Currant
Worm Fly are so generally inhabited by the
lai-va of a minute Hymcnopterons Parasite,
that among fifty eggs he only found four or five
which hatched out into Cunant Worms.

As these pages were going through the press,
we received trom the Editor of the Canadian
Entomologist a third parasite, which he had
himself ascertained to prey, not on the (igg of
the imported Currant Worm Fly, but on the
larva. This parasite is a small four-winged fly
belonging to the great Ichneumon Family, and
scarcely one-fifth of an inch long, with its front
wings very prettily ornamented each of them
with two dusky bands. A full description of it
(under the name of //e7wtYc/e5ne?na^it'orw«,n.sp.)
will probably appear befoi-e long, from the pen
of the Senior Editor, in the columns of the ex-
cellent Periodical just now referred to. This
very same species of Ichneumon-Hy had been
captured near Rock Island, 111., several years
ago by the Senior Editor; and as the Imported
Currant Worm has not as yet been introduced
into that region, we must conclude that this
Ichneumon-fly could not have been imported
into America from Europe along with this Cur-
rant Worm, but that in all probability it is an
indigenous species. Hence we have additional
proof that, under certain circumstances, native
American parasites can, and actually do, ac-
quire the habit of preying upon European in-
sects when the latter are imported into America.
It is certain, however, that they will not do so
in all cases without exception ; for although the
AVlieat Midge, or Red Weevil as it is incorrectly
termed in the West, invaded our shores some
forty or fifty years ago, not a single parasite has
yet been discovered to prey upon it in this
country, although there are no less than three
that prey upon it in Europe.

The Sawfly Family (Tenthredo), to which
both this and the next species to be noticed
belong, derives its name from the *< ovipositor"
or egg-laying instrument being modified so as
to mimick the blade of a saw. Under the mi-
croscope — and in the larger species even under
a good lens— it will be seen that the lower edge
of each of the two horny blades, ol which this
instrument is composed, is furnished with very



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THE AMERICAN ENTOMOLOGIST.



19



fine teeth, the c^hape of which differs in different
species. With this tool the female l3y saws into
the textare of the leaf or of the twig, in which
the instinct of each particular species teaches it
to deposit its egg ; and — wondeiful to relate —
it was demonstrated long ago that the eggs thus
deposited inside the suhstance of the plant,
which is to supply the future food to the young
larva as soon as it hatches out, actually grow
and derive nourishment from the sap of that
plant, so as often to attain double their original
size. Hence we may see at once why the eggs
are deposited by this group of insects in such
situations as these, and why Nature has provided
the female Sawflies with saws in their tails.
But — as the thoughtful reader will perhaps have
ali-eady observed— our Currant Worm Fly lays
its eggs upon the surface, and not in the intenor,
of the leaf, glueing them thereto by some adhe-
sive fluid which it secretes for that purpose.
And we may add tliat there are a few other
Sawflies — such for example as the Rosebush
Sawfly (Selandria roscB) — which do the very
same thing, and consequently, as well as our
species, can have no use for any saws at their
tails. If, therefore, as was formerly the almost
nniversal belief of the scientific world, each
species whether of animals or of plants was
independently ci*eated, with all its present
oi^us and instincts, and not derived, as is the
more modern doctrine, from the gradual modi-
fication of pre-existing species through a long
series of geological ages, wo might naturally
expect our Currant Worm Fly, and the Rose-
bush Sawfiy and such few other Sawflies as
practice similar modes of laying their eggs, to
have no saws at all. For why should nature,
when she is creating new species, bestow an
instrument upon a particular species which has
no occasion whatever to use that instrument ?
In point of fact, however, all female Sawflies,
no matter what their habits may be, possess
these saws, though in one genus (Xt/ela) the
saws, instead of being hard and horny through-
out, are said to bo soft and membranous above
and below;* and in certain other Sawflies,
though they are as hard and horny as usual,
they are degraded and — to use the technical
term — ** defunctionated." This will be seen at
once from an inspection of the following draw-
ing (Fig. 10) copied by ourselves from
nature and very highly magnified. Here a
represents the two saws of the female of
the Willow-apple Sawfiy {NeinatiLs salicis-
pomumy Walsh), which belongs to the very



[Fig. 10]



• See Weatwood s Introduction^ II, p. 95.




same genus as our Currant Worm Fly. Now,
we know that the female of the Willow-apple
Sawfiy deposits a single egg inside the leaf of
the Heart-shaped Willow (Salix cordatd) about
the end of April, probably accompanying the
egg by a drop of some peculiar poisonous fiuid.
Shortly afterwards there gradually develops
from the wound a round fieshy gall, about half
an inch in diameter, and with a cheek as smooth
and as rosy as that of a miniature apple ; inside
which the larva hatches out and upon the fiesh
of which it feeds. Of this gall we propose to
present a figure to our readers in the next num-
ber of our Magazine, in illustration of a Second
Article on "Galls and their architects." In
this particular case, therefore, as the female
Fly requires a complete saw with which to cut
into the Willow leaf, nature has supplied her
with such saws, as is seen at once from Figure
10, a. Now look at Figure 10, b, which is an
accurate representation under the microscope
of the two saws of our Currant Worm Fly.
it will be noticed at the very first glance, that
although the blade of the saw is there, the teeth
of the saw are almost entirely absent.

What, then, are we to make of these and many
other such facts? Manifestly the teeth of the
saw are in this last species degraded or reduced
to almost nothing, because the female Fly,
laying her eggs upon the surface of the leaf, and
not cutting into the substance of that leaf as
does the female of the Willow-apple Sawfiy,
has no occasion to perform any sawing process.
But why, it will be asked, is the blade of the
saw there in its normal size and, with the excep-
tion of the degradation of the saw-teeth, as com-
pletely developed as in the other species, when
such a tool can not be necessary for the simple
process of glueing an egg on to the surface of a
leaf ? The modern school of philosophers will
reply, that this is so, because the primordial
Sawfiy, in the dim far-away vista of bygone
geological ages, had a complete pair of saws,
and our insect is the lineal descendant of that
species, slowly and gradually modified through
a long series of years, so as to conform more or
less to the change in its habits. On the other



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THE AMERICAN ENTOMOLOGIST.



hand the old school of philosophers, who believe
that every species was independently created,
will argue that this is so, in order to ** complete
the System of Nature," and " carry out the Plan
of the Creation," and " give full and free expres-
sion to the Thoughts of the Creator." Possibly
this may be the true solution of the difficulty ;
but — and we say it in no irreverent spirit— what
should we think of a Potter, who made all his
teacups without exception with handles ; those
for which handles were required with complete
ones such as you could put your finger through,
and such cups as were not wanted to have any
handles at all, with solid unperforated ones,
such as would be nearly useless? And what
should we say, if the Potter's friends were to
gravely argue, that he took all this unnecessary
trouble in order "to complete the System of
Art," and "carry out the Plan of the Tea-
drinker," and "give full and free expression to
the Thoughts of the Potter"?

The Native Currant Worm.

{Prutiphora grossularto}, Walsh.)
Like the Imported Currant Worm, this worm
produces a Sawfly, which, however, belongs to
a different genus {Pristiphord) , chiefly distin-
guishable from the other one {Nematus) by the
front wing lacking what is technically termed
the "first submarginal cross-vein." In Figure
11, 6, we give a magnified drawing of the female
of this fly, and if the reader will look at this
drawing and compare it with that of the Imported

IFig. 11.]




( olors— (a) f^reen and black ; (6) black and honey-yellow.

Currant Worm Fly (Fig. 7, a and 6), he will
see that there is in each of them but one cell, or
" pane " as it might be termed, on the upper
edge of the front wing towards its tip. This is
technically called "the marginal (or radial)
cell." Now let the reader look a second time
at these two figures, and he will see that, under-
neath this " marginal cell," there is a tier of
four cells in the one genus {Kematus) and a tier
of only three cells in the other genus {Prlstl-
phora), the first or basal cross-vein being absent
or " obsolete " in the latter, so as to leave the



first or basal cell extravagantly large. These
three or four cells, as they underlie the "mar-
ginal cell," are technically known as " the
submarginal (or cubital) cells ;" and upon the



Online LibraryAndrew P. (Andrew Preston) PeabodyThe American entomologist: → online text (page 6 of 26)