Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: The fall army-worm, southern grass worm (Laphygma frugiperda, Smith and Abbott)
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 Material Information
Title: The fall army-worm, southern grass worm (Laphygma frugiperda, Smith and Abbott)
Series Title: Bulletin ; University of Florida. Agricultural Experiment Station - 40
Alternate Title: Fall army worm
Physical Description: p. 505-512 : ill. ; 23 cm.
Language: English
Creator: Quaintance, A. L ( Altus Lacy ), 1870-1958
Publisher: Florida Agricultural Experiment Station
Place of Publication: Lake City Fla
Publication Date: 1897
Copyright Date: 1897
Subject: Fall armyworm   ( lcsh )
Fall armyworm -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Statement of Responsibility: by A.L. Quaintance.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00024524
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAB6180
ltuf - AEN1429
oclc - 18154940
alephbibnum - 000920989

Full Text



Agricultural Experiment


The al A&rmy-Worn: southern Gras Worm


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HON. WALTER GWYNN, President...... .......... Sanford
HON. F. E. HARRIS, Ch'n Executive Committee ....... .Ocala
HON. A. B. HAGEN, Secretary. .................Lake City
HON. S. STRINGER ........... ... ........ ... .. ..Brooksville
HON. H. W. GELSTON ........... ............... .DeLand
HON. WiM. FISHER ..... ... ........ .............. Pensacola
HON. H. S. REES ................ .... ...Live Oak.


O. CLUTE, M. S., LL. D .. ....... .................. Director
P. H. ROLFS, M. S.............. Horticulturist and Biologist.
A, A. PERSONS, M. S.............................. Chemist
A. L. QUAINTANCE, M. S ............... Assistant in Biology
JOHN F. MITCHELL. .............. Foreman of Lake City Farm
J. T. STUBBS ....... ... Supt. Sub-Station, DeFuniak Springs
W. A. MARSH .................. Supt. Sub-Station, Myers
J. P. DAVIES, B. S.................. .. Assistant in Chemistry
LIBRARIAN........ ............................ Lake City

Thl Fall Arm-Worm: SoUUh GUIr rass Worim.
(Laphygmafrugiferda, Smith and Abbott )

Reports from several localities in the State indicate that the
fall army-worm has been unusually abundant and destructive
during the late spring and early summer of the present year. As
there is yet considerable time before cool weather will check
their propagation and ravages, it has been thought best to pub-
lish this circular of information relative to their habits and treat-
ment, in the hope that it may be of value in keeping this pest in


Fxi. I-a, larva; b, showing head, FIG. 2.-a moth, or adult. (From
enlarged. (From Riley.) Riley.)
This insect also occurred last year in considerable numbers.
During the latter part of August, and the first two weeks of
September, they were reported as very destructive to crab-grass,
and other grasses that were grown for hay. The present year
they have been much more numerous, and an earlier brood than
that of last year has been responsible for the damage. This fact
indicates that the conditions governing their development have
been more favorable this year than last, and if these favorable
conditions continue, we may expect that the next brood, proba-
bly late in August or early in September, will be a very large one,
and unless properly controlled may occasion considerable loss
to the hay and other crops throughout the state.

The fall army-worm has been frequently confused-with the
true army-worm of the North, Leucania unipuncta. But it
should be known that these are two distinct species, differing
considerably in their habits and food plants. The fall army-
worm is much more common South than North, and has been
frequently reported from most of the Southern States. The true
army-worm does not occur to any extent in Florida.

The insect has a wide range of food plants, as corn, oats,
rye, cotton, garden vegetables, and in fact, almost any succulent
plant may be attacked; it feeds more usually, however, on
various grasses. In Florida it seems to be partial to crab-grass
and crow-foot.
July 3rd, the crab-grass in the orchards on the Experiment
Station was observed to be badly infested with this insect. In
one orchard the larvae occurred in millions over an area of sev-
eral acres, and the heavy growth of the grass was being rapidly
consumed. The leaves and tender stems are eaten, and even the
larger and older stems are frequently eaten quite low down. In
the course of a week the grass had been eaten quite down to the
ground over a considerable part of the orchard, and the larvae
were working slowly out to the less defoliated areas. Several
larvae may feed quite close together on a single stem, eating
the leaves, the leaf-sheath or the stem. In feeding on the leaves,
they feed mostly on the edge, eating in toward the mid-rib; the
mid-rib is usually eaten down to near the stem, where a shurt
ragged remnant of a leaf is left. The leaf-sheath is usually quite
riddled with holes, or eaten off entirely. The stem is usually at-
tacked after the leaves are about consumed, and is eaten from
above downwards. The harder portion is frequently much
chewed into.
In some cases, it may be supposed that these insects are of
decided advantage, in keeping down the grass between rows of
corn or cotton, but where it is desired to cut the grass for hay,
their assistance becomes an injury; and it is well to remember
that the larvae may attack the crops themselves, in case the
grass is devoured before they have attained their growth, and

are ready to pupate. The next brood also might 'give serious
Eggs-The eggs of the fall army-worm are deposited in
small clusters, and often in layers, two or three layers placed one
above the other. This whole egg mass is usually covered with
the yellowish colored hairs from the abdomen of the female. An
individual egg is almost spherical in shape, pale fulvous in color,
and marked and ribbed much as illustrated in figure 3, a, show-
ing the egg of Agrotis saucia enlarged. The eggs are usually
placed on the under side of leaves of the food plant, but they
have occasionally been found on leaves upon which the larvae
are not known to feed.

FIG. 3.-a. an egg of Agrotis saucia, enlarged;
b, egg-cluster, natural size. (From Riley.)
Larva-The fall army-worm is illustrated in figure I, a,
about the natural size when full grown. In length the larva
measures about one and one-half inches. In the color there
is considerable variation, and also in the markings. The general
ground color varies from pale brown to dirty green. The dor-
sum, or back, is brownish with a narrow line running down the
middle. On each side, just above the spiracles, or breathing
pores, is a'rather broad, dark strip extending down the body; it
is about one-third as wide as an individual segment is long.
This dark band is bordered above by a narrow strip of yellow.
Below, the larva is a dirty greenish white, unmarked. The head

is pale yellowish brown, with a distinct white mark, shown in
figure I, b. Thoracic legs well developed; prolegs normal. The
shield or dorsum of prothorax is somewhat darker than body,
with the dorsal line and the yellow line bordering the dark sub-
dorsal line, extending conspicuously through it. There are
numerous black shiny tubercles distributed over the body; from
each of these, arises a dark hair-like bristle. On the second and
third segments these turbercles are arranged in a transverse
row, and are quite large. On segment eleven the dorsal tuber-
cles are arranged in the form of a square, while on the twelfth,
they have the form of a trapezoid.
Pupa-The pupa is of a bright mahogany brown color,
one-half inch in length. The caudal end terminates in two
diverging horns, forming a fork.
Adult-The moth into which the fall army-worm develops
is illustrated in figure 2, a. This figure indicates its natural size.
The wing expanse is a little less than one and one-half inches:
the body and head measure a little more than one-half inch. The
fore-wings above, are more usually dark ash gray in color, varie-
gated with fulvous, bluish white, and smoky brown. There is,
however, much variation in the shade of the fore-wing, and in its
markings. The hind-wings are pearly white, and transparent,
margined with dusky, which is heaviest at the apical end. The
entire under surface of the wings has a pearly lustre varying to
fulvous. On the abdomen below, are four pairs of small black
dots; the tip of the abdomen, below, ends in a bunch of rufous
colored hair-like scales.
The injury is done by this insect in its larval or caterpiller
stage. After hatching from the egg, the larva soon begins to
feed; during its earlier stages, it feeds mainly upon the leaves,
eating out the parenchyma in long narrow grooves, parallel to
the margin of the leaf. As the larva grows rapidly, it soon be-
gins to eat along the margin of the leaf, as previously men-
tioned. When ready to pupate, it works an inch or so below the
surface of the soil, and there makes a small cavity or cell,
cementing the sand together with a small amount of silk. From
one to tNvo days after this cell has been formed, the change to

the pupa occurs. This condition lasts for about seven days, when
the adult appears.
There seems to be considerable regularity as to the occur-
rence of broods, although larvae of various sizes may be ob-
served at the same time. But these all seem to pupate within a
short time of each other, and a field may be badly infested, and
a week later be quite free from them. The time of the appear-
ance of the adults of a brood during the summer, appears to be
confined to a few days.
Fortunately there are several natural enemies of this insect
which serve greatly to keep it in check. In the field, a large red-
dish-brown wasp (Polistes bellicosus?) was frequently observed
to destroy these larvae. After catching a worm, the wasp re-
moved from the skin the food in the alimentary canal, gradually
working it forward and out through a cut in the skin near the
head. The remaining portion was then rolled up and chewed
awhile with the mandibles. This was possibly swallowed,
though the act was never observed.
There are several other species of wasps that attack these
larvae. Much good work is also done by a species of Tachina
fly, an insect much resembling the house fly, but larger. These
flies were bred from larvae placed in .breeding cases, in consid-
erable numbers. The maggot of the fly devours the interior of
the worm, causing its death. Another fly, a species of Bomby-
lid, or bee fly, was also bred from these larvae in such numbers
as to indicate their value as insect friends.
Various other insects probably aid in the destruction of the
larvae of the fall army-worm, as ground-beetles, tiger-beetles,
lady-birds, the spined soldier bug, wheel-!bug, asilid flies and
mantids. Toads are also of great value, and should always be
encouraged around fields and gardens.
The value of the hay crop is sufficient to make it profitable
to take steps to check the ravages of'this insect; and aside from
their damage to grass designed for hay, there is the danger of
their further increase in succeeding broods to such an extent
that various other more valuable crops might be attacked.

The old adage, "a stitch in time," is quite applicable in
treating insects, and is particularly applicable to the species under
consideration. The earlier broods of the larvae should be care-
fully watched for, and destroyed, thus greatly reducing the
chances for their abundance in succeeding broods. These
broods are usually more or less gregarious in the fields, and it is
quite practicable to destroy them with Paris green. This should
be thoroughly mixed with water in the proportion of one pound
of Paris green to 125 to 15o gallons of water, and applied thor-
oughly to the infested grass with a spray pump. There is
usually difficulty in getting the spray to stick to the leaves of
grasses, and it has been recommended to put enough soap suds
in the water to make it more adhesive. The use of cheap mo-
lasses would probably accomplish the same result. The spray
may also be used against the larvae when they have attacked
other plants. If plants are to be sprayed that are easily "burned"
by Paris green,a poundof powered or quick-lime should be made
into a thin paste, and this poured into the mixture of Paris green
and water. One or two good rains after spraying, would be suf-
ficient to wash the poison from the grass, and it could safely be
cut for hay.
If the larvae are not observed until they are quite abundant,
and the grass is being rapidly devoured, it would probably be
best to plow them under as deep as is practicable. This would
destroy the younger larvae, and if the older larvae pupated, they
would be so deep in the soil that the moths would probably not
be able to work their way to the surface. And it is not improb-
able that the majority of these insects would be males, as.various
experiments seem to indicate that when animals are under-fed,
and surrounded by unfavorable conditions during their earlier
stages, the male sex greatly predominates. A late crop of hay
could in many cases be cut from fields thus plowed.
SWhere practicable, a large roller could be used to crush the
larvae. This would be practicable in oat or rye fields.
The foliage of orchard trees is sometimes attacked, after the
grass has been quite consumed. To prevent larvae from crawl-
ing up the trees, a roll of cotton should be tied rather loosely
around the trunk, a short distance above the ground.

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