CIRCULAR No. 38, SECOND SERIES.

United States Department of Agriculture,

DIVISION OF ENTOMOLOGY.

THE SQUASH-VINE BORER.

(Melittia satyriniformis Hbn.)*

GENERAL APPEARANCE AND METHOD OF WORK.

Fig. 1.—Melittia satyriniformis: a, male moth; b, female, with wings folded in natural position
when at rest; ¢,eggs shown on bit of squash stem; d, full-grown larva, in situ in vine; e, pupa;
f, pupal cell—all one-third larger than natural size (author’s illustration).

One of the most troublesome of the many enemies of squashes,
pumpkins, and other cucurbits is the squash-vine borer. In many
localities this species surpasses all other squash insects in point of
injuriousness.

Damage is due to the larvee boring through the stems, causing
them to rot at the affected points and become severed from the vine,
or so injuring the vine as to cause the leaves to wilt and the plant
to die. The presence of the borer feeding within the stem is not
apparent at the commencement of the attack, but soon becomes
manifest through the presence of the yellowish powdery excrement
which it forces from its burrow in the stem and which accumulates

* Until recently this species was generally known as Melittia ceto, or cucurbitee.
For the reason of the change of name see writer’s article published in Bul.
19, n. s., Div. Ent., p. 38.

ro]

on the ground beneath, as well as by the sudden wilting and dying
down of the leaves. Wilting occurs soon after the larvae have made
considerable growth within. From one to half a dozen or more
larvee inhabit a stem, and often upwards of forty individuals have
been taken from a single plant; indeed, one grower has stated that
he once cut ‘*142 larve from a single vine.” The larvz work with
great rapidity and in a very short time are able to injure a plant so
that no fruit will mature. Injury is most noticeable near the bases
of the stems, where in course of time the vine becomes severed from
the roots and the whole vine dies.

The parent of this insect is a beautiful creature, a medium-sized
moth of the family Sesidee, or clear-winged moths. The fore-wings
are opaque, lustrous olive-brown in color, with metallic green refiec-
tions, and expand from less than an inch to nearly an inch and a
half. The hind-wings are transparent and veined as shown in the
accompanying illustration of the male (fig. 1, a). The abdomen is
conspicuously marked with orange or red, black and bronze, and the
hind legs are fringed with long hairs, red or orange on the outer
surface and black inside. The natural position of the moth when at
rest is shown by the figure of the female (0).

DISTRIBUTION.

As far as known this species is a native of the Eastern Hemis-
phere, and widely distributed and injurious in the United States
practically wherever squashes are cultivated. Available records
and examination of material in the collection of the U.S. National
Museum show that it has a range, embracing territory from the
New England States and Canada in the north, to the Gulf States
southward, and westward to the region beyond the Missouri River,
which comprises the major portion of the Carolinian and Austrori-
parian regions of the Upper and Lower Austral and a portion also
of the Transition life zones. Injury has been observed to be particu-
larly severe in recent years on Long Island and in New Jersey, Del-
aware, Maryland, Virginia, and the District of Columbia in the
east, and in Kansas and Nebraska in the west. Other States in
which injury has been noted include Maine, Massachusetts, Con-
necticut, Rhode Island, Georgia, Alabama, Mississippi, Louisiana,
Iowa, and Michigan. It is evidently of tropical origin, and occurs in
Mexico, where it is also widely distributed, in Guatemala, Panama,
Venezuela, Argentine, and the Lower Amazon.

FOOD HABITS.

The vines of squash and pumpkin form the chief food supply of
this species, but occasionally it attacks also gourd, muskmelon, and
cucumber. It does not, however, in the writer’s experience, attack

WY

melons and cucumbers when the other preferred crops are availa-
ble. The larvee bore through the stems from the roots to the base
of, and even through, the leaf-stalks, and sometimes attack the fruit
both of squash and muskmelon. Larvee have also been observed on
the wild balsam apple (Hchinocystis lobata), which is probably <
natural food plant.

Injury is greatest to Hubbard, marrow cymblins, and other late
varieties of squash, and is apt to be more acutely felt in small
gardens than when crops are grown for market. Even if the plant
survives attack it may not bear fruit, and often the grower loses a
large proportion of his crop year after year. Not infrequently entire
crops are destroyed.

NATURAL HISTORY.

This species is injurious only in the larval form. Although the
larvee are familiar objects to all squash growers, the moths are not
generally recognized as the parents of these pernicious borers.

The moths, unlike most others, fly only during the daytime and in
the heat of the day. Toward twilight they become less active and
may be seen sitting quietly on the leaves of their host plants. Both
when in flight and when at rest the moths are singularly wasp-like
in appearance.

Time of appearance of the moth.—Approximately it may be
stated that the moth appears as soon as the vines are sufficiently
advanced to serve for oviposition and the subsequent subsistence of
the borer larvee within their stems. Indications are that as far south
as the District of Columbia the moths make their first appearance in
the field sometime in May or at least early in June, as larvee nearly
matured have been found by the middle of July. In New Jersey,
according to Dr. J. B. Smith, the moths are abroad at or soon after
the beginning of June; on Long Island from the middle to the last
of June. In Massachusetts, according to Harris, they appear about
the plants the second week in July. We thus have considerable
variation in time of earliest appearance dependent upon season and
locality, a variation to be expected in a species of so wide a range.

The egg and oviposition.—The eggs, which are oval and dull red
in color, are laid upon all parts of a plant, from the roots to the buds
and petioles, but chiefly along the stems, though in some varieties of
squash, it is said, nearer the base of the stem than otherwise. Ovi-
position is very rapid, the moth flitting from hill to hill leaving an
egg ineach. A single moth may lay as many as 212 eggs. The
eggs hatch in from six to fifteen days after they are deposited, and
the larvee are said to attain full growth four weeks or more later.
This period will undoubtedly vary in different temperatures accord-
ing to the season of the year when oviposition takes place.

4

Eggs are shown a little larger than natural at c of figure 1, and
much magnified at a and b of fig. 2, ¢ showing the sculpture.

The larva.—The larva is a soft, whitish, grub-like caterpillar of
nearly cylindrical form, with a small, dark head and a few very
sparse hairs on each segment. . Larvee in the earlier stages of growth
are illustrated by d, e, and f, of fig. 2. A full-grown larva is shown
in profile within an open stem at fig. 1, d, and the head and first two
thoracic segments appear in fig. 2 at g. Mature larvee measure
about an inch (25 mm.). In the District of Columbia full-grown
larvee, as already observed, occur as early as June 16; in New Jersey
late in July, and are to be found upon the vines in different stages
in October; at Washington as late as the second week of November.

After attaining maturity the larvee desert the stems and enter the
earth, burying themselves to the depth of one or two inches, and
form their cocoons in which
they transform to pupa.
The cocoon (shown at f,
fig. 1) is constructed of silk
and coated externally with
fine particles of earth which
adhere by means of some
gummy secretion of the
larva.

The pupa or chrysalis
(shown in profile at e, fig. 1)

FiG. 2.—Melittia satyriniformis: a, egg as seen from above; sek Hi
b. same from the side showing sculpture; e, sculpture of Measures about ¢ inch in
egg greatiy enlarged ; d, newly-hatched larva; e, haltf- length (16 mm.). It is shin-
grown larva; f, head of same from side; g, head of ma-. c
ture larva from above; a,b, and d, muchenlarged ; ¢, f, NS mahogany brown in

and g, less enlarged. (Author’s illustration). eolor and its head is orna-

mented in front just above and between the eyes with a horn-like
process. By means of this the pupa cuts its way out of one end of
its cocoon and by the aid of the abdominal hook-like spines forces
itself to the surface of the earth before transforming to imago.

Number of generations.—The question of the number of genera-
tions produced annually in the different temperature localities which
this insect inhabits has been solved by recent observation, the results
serving to indicate that it is practically single-brooded on Long
Island and northward; that there is a tendency to two broods in New
Jersey, the moths in exceptional cases completing their transforma-
tions late in August or September; that in the latitude of the Dis-
trict of Columbia the species is partially double-brooded, a larger
portion of the moths, we may assume, developing as a second gene-
ration here than in New Jersey; and that in the Gulf States this
species is undoubtedly fully two-brooded.

PREVENTIVE AND REMEDIAL MEASURES.

This borer is an exceptionally difficult insect to control, as ordinary
insecticides are of no value against it after the insect has once entered
the vines, and repellents are also practically useless. We are, there-
fore, dependent upon cultural methods for relief.

Knowing, as we do, that the insect passes the winter in the fields
which it has ravaged, it should be superfluous to caution growers
not to plant squashes in the same ground in successive years.

Early squashes as traps.—Good results have been obtained by
planting as a trap crop and as early as possible a few summer
squashes, such as crooknecks and early cymblins, before, and between
rows of, the main crop of late varieties. The summer squashes
attract the insects in such numbers as to leave a smaller number to
deal with upon the late or main crop. As soon as the early crop is
gathered, or earlier if the ground is needed for the main crop, the
vines are promptly raked up and burned to destroy all eggs and
larvee which they may harbor, and the same treatment is followed
after gathering the late varieties. This method, according to Dr.
Smith, has proved profitable where used in New Jersey, and should
produce good results farther north. Southward where two well-
defined broods appear it might not be so productive of good, but it
should be given a thorough test.

Fall harrowing and deep spring plowing.—Experiments
recently conducted by Mr. F. A. Sirrine of the New York Agricul-
tural Station at Geneva, N. Y., show that this species can be greatly
reduced by lightly harrowing the surface of infested squash fields in
the fall so as to bring the cocoons of the vine borer to the surface,
where they will be exposed to the elements, and then plowing in the
spring to a uniform depth of at least six inches so that the adults
will not be able to issue.

Other cultural methods.—When the vines have attained some
length parts of them should be covered over with earth so that sec-
ondary roots will be sent out to support the plants in case the main
root is injured by the borer. Keeping the plants in good condition,
free from disease and other insects, and well nourished, with the
assistance of manure or other fertilizer if necessary, will also aid the
plants to withstand borer attack. When vines are so badly infested
as to be incapable of bearing fruit they die usually at once, and they
should then be promptly taken out and burned. ‘The old vines should
also be destroyed as soon as the crop is made.

Cutting out the borers.—The old-time remedy of cutting the
borers out of the vines, although laborious, is of value, and about
the only method open for employment after they have entered the
vines. As several individuals often infest a single vine, it is best to
cut longitudinally, so as not to sever the vine from the root stalk.

If the wound made by cutting be afterward covered with moist soil
it willassistit to heal. The location of the borer in the vine can readily
be detected by the accumulation of its yellow ‘‘frass” or excrement
at the point where it is working, and which is kept open for the
extrusion of this matter.

Capturing the moths.—This species may be held in partial sub-
jection by keeping a sharp lookout for the parent moths, which are
readily seen and not difficult of capture toward dusk or in the cool of
the morning, when they are comparatively inactive. The female may
be easily caught, just as she alights on a vine for oviposition. *

Summary.—lf the grower would make certain of securing a good
crop in localities where this and other enemies of the squash occur
in their most destructive abundance, it will be necessary for protec-
tion against this borer to observe most of the following precautions,
and, if possible, secure the cooperation of his neighbors in their
observance :

(1) Not to plant in or near infested ground.

(2) To plant early varieties for the protection of late squashes.

(3) To harrow infested fields lightly in fall and plow deeply in
spring, to prevent the moths from issuing.

(4) To encourage the growth of secondary roots by covering the
stems with earth.

(5) To destroy dead vines and old plants as soon as the crop is
made.

(6) To keep the plants in vigorous condition free from other insects
and disease.

(7) To cut out such borers as may succeed in entering the vines in
spite of the employment of other remedial measures.

The capture of the moths before egg deposition is also advisable.

ln proof of the practicability of this, the writer refers to the testimony of
Mr. J. V. D. Walker in Insect Life (Vol. IV, pp. 271, 272).

F. H. CHITTENDEN,
Assistant Entomologist.

Approved :
JAMES WILSON,
Secretary of Agriculture.

WASHINGTON, D. C., April 22, 1899.

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