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Psyche 4:48-51, 1883.

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PSYCHE.
[May-June 1883.
ON AN EGG-PARASITE OF THE CURRANT SAW-FLY (NEAL4 TVS VENTRICOSUS).
BY JOSEPH ALBERT LINTNER, ALBANY, N. Y.
[Read before the American Association for the Advancement of Science, at its Montreal meeting, 29 August 1882.1
Dr. Asa Fitch, in his 12th Annual
report on the insects of New York for
the year 1867 (Trans. N. Y. state
agric. soc. for 1867, 1868, v. 27), p.
931-932, made the following reference
to this insect :
"As none of the foreign accounts
which we have seen allude to any para-
sitic enemy of this currant saw-fly, it
seemed quite improbable that it would
in this country meet with any such
enemy, to lighten from us the task of
combatting it and diminishing its devas- tations. But our valued friend J. A.
Lintner, of Schoharie, greets us with
the glad tidings that he has discovered
we have such a foe to this formid-
able scourge. An egg parasite of this
siw-fly inhabits our st-ite, an exceedingly minute hymenoptero~~s insect, which
inserts its eggs into those of the saw-fly, that its young may subsist upon and con- sume the contents of those eggs. This
diminutive little fly has probiibly existed hitherto upon the eggs of son12 one of
our American siw-flies similar in size
to those of the currant saw-fly ; iind it has now discovered that the eggs of this newly arrived foreigner are equally wdl
adapted to its wants. And so multi-
plied has this little fried of the gar-
dener become, that in Utica Mr. Lintner
finds that among fifty eggs of a saw-fly upon a currant leaf, there will not be
more than four or five that will hatch
currant worms, all the rest being occu-
pied by the little maggot, the young of
this parasite. At Schoharie, also, where the saw-fly has arrived more recently
than at Utica, he finds this parasite
is now beginning to appear. Every-
where this little creature is no doubt
following upon the tracks of the si-w-
fly, and within a very few years after
the one arrives in any place the other
will be there also, and will speedily
become so multiplied as to quell and
extinguish it. This is a most impor-
tant discovery, and renders it quite
probable that in this country this cur-
rant worm can never be but a ternpo-
rai-y evil. Whenever circumstances
favor it and enable it to multiply and
become numerous in any section of our
country, this little enemy, its mortal foe, will speedily be there to subdue and
stamp it down. Thus nicely are the
works of nature balanced, and no crea-
ture is permitted to usurp a place in her domain which does not belong to it."
-
The specimens of the parasite obtained
by me, at the time referred to in the
above notice, were submitted to a friend who had made study of the group
to which they belong, who believed
them to be an undescribed species, and
was only able to give them a doubtful
generic reference. They were subse-
quently destroyed, and from that time
until the present year (an interval of
fourteen years), although 1 have con-
Pu&f 4 048-51 (pre.1903). hfp //psyche aitclub o@#4-0048 htd



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May-June lsS3.~ PSYCHE. 49
tinued to search for them, I have been
unable to obtain the species.
Its rediscovery by me the present year,
and the determination of the species,
lend additional interest to the notes
upon it that I made at its first observa- tion, at Utica, N. Y., in June 1866,
and I therefore transcribe them from
my note-book :-
I had collected a number of currant
leaves upon which the currant saw-fly
had deposited eggs, and was counting
the eggs upon each to obtain the average number per leaf, when I noticed an
occasional brown egg among them, ap-
pearing somewhat abnormal in shape.
On placing them under a lens a resem-
blance to a pupal form was detected.
I at once suspected the presence of the
parasite for which we had been hoping.
Although there seemed to be but the
merest chance of discovering at large
an insect so minute as this must neccs-
sarily be, I instituted a careful search of the currant bushes in the garden, and in a short time had the great gratification of discovering a minute speck moving
among the eggs, which under my lens
revealed a form which left scarce room
for doubt of its parasitic character.
During the day I detected several more
of the kind upon the leaves containing
egg-deposits, affording strong evidence
of their relationship. A few days there- after (perhaps a week), in a small phial in which I had placed some eggs that
I suspected of having been parasitized,
I had the delight of seeing several of
the familiar forms of my currant-leaf
acquaintances, and the ruptured pupa
cases from which they had evidently
escaped.
The following year (1867) there was
a marked diminution in the number of
currant-worms observed, and a corres-
ponding increase in parasitized eggs.
Many of the leaves had not been visited
by the parasite, but of those that gave
evidence of such visit, the work of de-
struction was almost complete, for of
several leaves bearing each from thirty to forty eggs, all but five or six were trans- formed into parasitic pupae.
In June 1868, I was able to make, at
Schoharie, N. Y., the following obser-
vations upon the oviposition of the
parasite within the eggs of the currant
saw-fly :-
In a small phial in which had been
placed some parasitized eggs of the saw- fly, a male and female parasite had
emerged. That I might observe their
actions I introduced a piece of currant
leaf having upon it some eggs which
I had just seen deposited. No evidence
was given that the female was aware
of the presence of the eggs, but after
several minutes traveling around the
glass, she moved upon the leaf, and in
passing over and beneath it, seemed
to meet with them accidentally. She
paused, and then began a careful inspec- tion, walking over them several times,
and constantly palpating them with her
antennae. Then, satisfied with her ex-
amination, she attached herself to one
of the eggs, appressed the tip of her
abdomen to it, and remained in this




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position motionless for the space of two- and-a-half minutes, during which time
an egg, doubtless, was inserted, although the pocket lens with which the observa-
tion was made did not disclose the fact, The motion of her antennae then recom-
menced, and I expected to see the
operation just witnessed repeated upon
another egg; but, to my surprise, she
merely changed position-again applied
the tip of her abdomen to a different
part of the same egg, and remained
at rest for about the same space of time as before. Three times I witnessed this
performance, and it is therefore pro-
bable that three parasitic eggs were
placed within the one of the currant-
fly. Unfortunately an interruption pre-
vented me from noticing if the remain-
ing currant-fly eggs were similarly
parasitized, and the number of eggs in-
troduced in each ; and much to my
regret, the eggs were accidentally de-
stroyed before my observations could be
made upon their transmutation into
parasitic pupae. The pupa cases are
dark brown, disclosing some of the
outlines of the contained pupae, some-
what flattened, broader than the original egg, but of about its length. The in-
sect is apparently one of the chalcididae, having a broad head, long and elbowed
antennae, ovoid anterior wings, nearly
veinless, beautifully iridescent, deli-
cately fringed and haired ; the posterior wings are almost linear ; the abdomen is short, not reaching the tips of the wings. This year (1868) is probably the
first appearance of the parasite at
Schoharie, as I could only discover about [May-June 1683.
a dozen individuals. Its progress seems
to be from west to east, corresponding
with that of the currant-worm.
The rediscovery of the parasite the
present year (1882) was made in my
garden at Albany, upon a solitary cur-
rant bushgrowing there. The parasitized
eggs were enclosed in ft bottle, and in a few days the insects emerged. That I
might multiply and aid in the distribu-
tion of an insect which had already
shown its capability for usefulness, I
visited another garden in the city to
obtain eggs of the currant-fly for para- sitization by my confined individuals.
To my surprise, the parasite was here
found in strong force, for in the ex-
amination of a long row of currant
bushes containing many eggs, I could
not find a single egg-bearing leaf which had not been visited, and the destruc-
tion of the eggs ensured. A large nurn-
ber of leaves were collected, each
bearing perhaps from forty to fifty
parasitized eggs. Reserving a few of
these for study and for propagation, the remainder were made up in small par-
cels of about a half-dozen each, and
mailed to entomological friends in vari- ous parts of the United States and
Canada, with the request that they be
pinned upon currant-bushes among the
leaves where the currant-fly eggs were
to be found. The introduction of para-
sites in this manner into localities where they had not previously occurred, has
been shown to be practicable; and in
consideration of the great importance of parasitic aid in the destruction of our




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ay-June 1883.1 PSYCHE. 51
insect pests, I sincerely hope that my
efforts to distribute this very efficient parasite may prove, from observations
to be made hereafter, to have been suc-
cessful.
Examples of the insect were sent by
me to Mr. L. 0. Howard, of the De-
partment of agriculture at Washington,
a gentleman who has made special
study of the family to which it pertains, viz., the ~Jzalcididae. He informs me
that there is no doubt of its being the
species described and named by Dr.
C. V. Riley in 1879 (Can. entom.,
Sept. 1879 v. I I, p. 161-162) as Tricho- patnma fretiosa, examples of which
had been reared, at Washington, from
eggs of the cotton-worm moth, Aletia
arg ilZacea Hiibn., collected in Alabama. The description is reproduced, with
additional information, in Prof. J. H.
Comstock's Report upon cotton insects
(Washington, 1879), p. 193. It has
since been extensively reared from eggs
of the same moth collected in Florida,
by Mr. H. G. Hubbard. It has also
been bred at the U. S. Department of
agriculture from eggs of an unknown
noctuid moth occurring on orange trees,
and from Aleyrodes.
Dr. Riley, from some structural
features, thought that it might be nec-
essary to establish a new genus for this species and one or two closely allied
ones, but Mr. Howard finds it to be a
true Trichogramma, as at first referred. Another species of the genus, Zl
minuta Riley,l has been reared from the
eggs of one of our common butterflies,
of extensive distribution, Limenitis
di.<;i//us. Parasitized examples of
these eggs have given from four to six
specimens of the minute creature, which, notwithstanding its specific name of
minuta, exceeds in size the microsco-
pic T. fretiosa, the latter being only
about 0.25 mm. in length.
In connection with the above notice
of the egg-parasite of the currant-fly,
it may be of interest to offer the follow- ing note of the oviposition of the cur-
rant-fly as observed by me, as its method has not to my knowledge been previ-
ously published :
June 7, 1868. Newtus ventricosus
was seen to deposit thirty eggs upon a
single currant leaf within one hour. In
the act of ovipositing, it curved the tip of its abdomen downward and forward,
directing its ovipositor toward its head, in which position the end of the egg is
seen to protrude and attach itself to the leaf-nervure, when the ovipositor is
withdrawn, and the egg left in position. Moving backward a very little, another
egg is similarly deposited, and in like
manner the operation is continued, until the leaf has its assigned quota, or the
supply of eggs is exhausted. The eggs
produced their larvae on June 14th.
I Third Annual report on the insects of Missouri, 1871, p. 153, fig. 72.




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