“{ THE ARTIFICIAL USE OF THE

‘| BROWN.TAIL FUNGUS

IN MASSACHUSETTS

WITH PRACTICAL SUGGESTIONS FOR
PRIVATE EXPERIMENT, AND A BRIEF
NOTE ON A~FUNGOUS DISEASE OF
THE GYPSY CATERPILLAR

sy A. T. SPEARE, Assistant PATHOLOGIST
HAWAIIAN SUGAR PLANTERS’ ASSOCIATION
and R. H. COLLEY, austin rteacainc

FELLOW IN. BOTANY, HARVARD UNIVERSITY

—

UNDER. THE DIRECTION. OF
F. W. RANE, STATE FORESTER
OF MASSACHUSETTS

BOSTON: WRIGHT & POTTER PRINTING COMPANY
STATE PRINTERS -- 18 POST OFFICE SQUARE

1912

PLATE I.

A winter nest with young laryce dead from the disease scattered all over the surface.

THE ARTIFICIAL USE OF THE

BROWN-TAIL FUNGUS

IN MASSACHUSETTS

WITH PRACTICAL SUGGESTIONS FOR

PRIVATE EXPERIMENT, AND A BRIEF

NOTE ON A FUNGOUS DISEASE OF
THE GYPSY CATERPILLAR

sy A. T. SPEARE, assistant PATHOLOGIST
HAWAIIAN SUGAR PLANTERS’ ASSOCIATION
and R. H. COLLEY, austin tTeacuine

FELLOW IN BOTANY, HARVARD UNIVERSITY

UNDER THE DIRECTION OF
F. W. RANE, STATE FORESTER
OF MASSACHUSETTS
|

BOSTON: WRIGHT & POTTER PRINTING COMPANY
STATE PRINTERS .- - 18 POST OFFICE SQUARE

1912

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QCT SO 1912
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APPROVED BY
Tue Stare BoarD OF PUBLICATION.
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INTRODUCTORY.

This report is published in order to acquaint our people with
the beneficial results to be derived from utilizing a fungous
disease in destroying the broWn*tait iifoth, which is so destruc-
tive to our deciduous trees ang. also-so:obnoxious to our people
on account of the rash incidént upon the contact of its hairs with
the human skin.

The report is based on a manuscript of Dr. G. P. Clinton, on
the manuscript and notes of Mr. A. T. Speare and on personal
observation and experiment by Mr. R. H. Colley, and was sug-
gested by the apparent success of experiments made by Dr. Ro-
land Thaxter of Harvard University at Kittery Point, Me., in
the summer of 1907.1 At this time former Superintendent
Kirkland of the Moth Commission became interested in the
matter, and on the advice of Dr. Thaxter the services of Dr.
G. P. Clinton of the New Haven Agricultural Experiment Sta-
tion were secured, and preliminary experiments were continued
under his supervision from May 12 to July 11, 1908. Dr. Clin-
ton was assisted during June and July by Mr. A. T. Speare, who
was later employed permanently by the State Forester to suc-
ceed Dr. Clinton, and who had immediate charge of the investi-
gation from July, 1908, until February, 1911, while during the
past year it has been in charge of Mr. R. H. Colley. All of
the laboratory experiments connected with this work have been
conducted in the cryptogamic laboratories or at the Botanic
Garden of Harvard University.

ACKNOWLEDGMENTS.

The State Forester and all concerned in the work wish to
acknowledge their indebtedness to Professor Thaxter for sug-
gestions as to experimental methods and for general direction
and advice. Through the courtesy of Dr. G. L. Goodale and
Mr. Oakes Ames, the directors of the Botanic Gardens, the suc-
cessful propagation of the disease through the winter and the

1 See Professor Hitchings’s report in Maine Dept. Agri. Bur., 3, 20,1908.

4

preparation of infection material on a large scale, have been
rendered possible.

Thanks are also due Mr. Worthley, assistant in moth work,
Messrs. Fiske and Burgess of the parasitic laboratory at Mel-
rose Highlands, and to the division and local superintendents
of the regular moth staff for their co-operation, and for cour-
tesies rendered.

For the work on the fungus of the gypsy caterpillar, which
has not as yet developed so satisfactorily as that on the brown-
tail, we are wholly indebted to Harvard University through its
friends in financing the expedition to Japan, where the disease
was secured. The kindly offices of Harvard University, through
Dean Sabine and his colleagues in assisting the State Forester
in making this work possible, are herewith heartily acknowl-
edged.

F. W. RANE,

State Forester.
Boston, March 22, 1912. :

THE ARTIFICIAL USE OF THE BROWN-TAIL FUNGUS IN
MASSACHUSETTS, WITH PRACTICAL SUGGESTIONS
FOR PRIVATE EXPERIMENT, AND A BRIEF NOTE
ON A FUNGOUS DISEASE OF THE GYPSY CATER-
PILLAR.

SOME FUNGOUS DISEASES WHICH HAVE BEEN USED
ARTIFICIALLY.

The conditions governing the artificial spread of a fungous
disease among insects vary according to the type of fungus used
and the characters and habits of the pest to be attacked. All
classes of insects have their fungous enemies, — some, like the
Entomophthoree, the species of Cordyceps and its Isaria con-
dition, as well as other forms belonging to the Pung: Imperfecti,
often causing serious epidemics, while others, like the Laboul-
beniales, may be comparatively harmless. The idea of using
fungous diseases in a practical manner to control the ravages
of noxious insects is not a new one, and as early as the middle
of the last century De Bary, Tulasne and others called the atten-
tion of agriculturists and orchardists to the importance of white
muscardine, Zsaria densa Link., as a natural check on destruc-
tive insect pests. Since the time this suggestion was originally
made there have been numerous more or less successful attempts
to use fungous diseases artificially, among which the following
may be mentioned.

Metchnikoff (1878) cultivated Metarhizium amsoplie
(Metch.) Sorokin, the so-called green muscardine, and infected
Anisoplia with the spores. Krassilstschik (1884) founded a
laboratory at Smelk in order to raise green muscardine in large
quantities, and the spores, spread on the beet fields to infect
Cleonus punctiventris, the beet weevil, started an artificial epi-
demic which is said to have killed from 50 to 80 per cent of
these destructive beetles. Rorer (1910) has also used the spores
of the same fungus, mixed with flour, in spraying sugar cane in
Trinidad to control the froghopper, with some success.

6

Cordyceps melolonthe Tul. has been employed against the
white grub, Melolontha vulgaris, in Europe, and Giard (1893)
records an attempt to use [saria densa against the same insect
in France, contrasting the results obtained with those of certain
American investigators. Buisson (1892) used Botrytis tenella
Sace. against the same pest.

Sporotrichum globuliferum Speg. has been used by Snow
(1889), Forbes (1888), Brunner (1902) and others on the
chinch bug in this country, but although various opinions have
been expressed as to the success of this work, the more recent
experiments of Kelly and Parks (1911) lead them to the con-
clusion that, although under certain conditions the fungus may
be very destructive in nature, its artificial propagation is not
to be recommended, an opinion in which Messrs. Billings and
Glenn (1911) also concur. Brunner has also used it on the
migratory locust in the Argentine Republic, and reports its
use in the fight against the same pest in Sterling, Col.

Spherostilbe coccophila Tul., Microcera sp. and Ophionec-
tria coccicola EK. and E. have been successfully employed (Rolfs,
1907, and Fawcett, 1908) against the San José and purple scale
of orange trees in Florida. During the last three or four years
the use of Aschersonia aleyrodis Webber, Aschersonia flavo-
citrina P. Henn and A’gerita Webberi Faweett (Fawcett, 1908,
Rolfs, 1908, and Berger, 1910) has been very successful in
checking the white fly in the citrus groves of Florida, a region
especially well adapted for such experiments, owing to the
fact that here these fungi grow naturally out of doors more or
less continuously throughout the year.

Of the Entomophthoree, although the group contains some
of the most destructive forms attacking economically important
insects, the brown-tail fungus appears to be the only form which
has been used artificially. That more of these forms have not
been used is probably due to the fact that their cultivation and
propagation is usually attended with the greatest difficulty.

THE BROWN-TAIL FUNGUS.
The fungus which causes the disease of the brown-tail cater-
pillar is a microscopic plant known technically as Hntomo-
phthora Aulice Reich, which has been long known in Europe

PLATE II.

a b c
Fig. 1.
FIG. 1.—a, gypsy moth larva from Japan killed by an HLntomophthora disease; b, a

tent caterpillar, and c, three brown-tail larvee killed by Hutomophthora Aulice, The
latter were kept in a dark chamber to develop an external growth of the fungus.

Fig. 2.

FG, 2.—This photograph gives some idea of the number of spores discharged. The
branch, crowded with dead and dying caterpillars, was laid ona sheet of glass in a
still room, and the white color is entirely due to the thousands of spores which fell
on the glass during the night.

7

and was first reported from this country by Dr. Thaxter in
1888. It has not only produced natural epidemics among the
brown-tails since they were first introduced, but it attacks vari-
ous other native species of insects, which are enumerated below.
It is closely allied to Entomophthora musce Cohn, a fungus
that attacks the common house fly, which may often be seen
dead on a window pane or mirror, where it becomes surrounded
by a white halo or whitish patch, due to the large number of

Fia. 1.— Diagram to illustrate the development and ‘discharge of spores.
At the tip of the club-shaped conidiophore a a rounded bud b develops
into the pear-shaped spore c. This spore is torn away at the collar d
when mature by internal pressure, and shot off from the conidiophore
f, as indicated by the arrow ate. Spores produced and discharged in
this manner are called conidia. At g is shown a germinating spore
with its young germ tube.

spores discharged on the glass. (Plate II., Fig. 2.) These
spores, called conidia, which are the fruit of the fungus, and
correspond in function to the seeds of higher plants, are ovoid
to pear-shaped (Plate VII., Figs. 1-4), with a papillate base,
and measure 25 to 35 by 28 to 40 thousandths of a millimeter.
If a spore comes in contact with a healthy caterpillar under
favorable conditions of moisture, germination takes place imme-
diately; that is, the spore sends out a thread-like germ tube.
(hie tg. Plate Nally, : Figs) 5-75) Plate VERE ig: -32,))
This germ tube pierces the integument and continues to grow

8

within the body of its victim for about five days after infection.
Germination may also take place on any moist surface, but in
such cases growth is usually very limited, and may result in
the production of secondary conidia (Plate VII., Fig. 8)
exactly similar to the primary conidia, which may be dis-
charged when mature and have the same power of infecting a
healthy larva. The conidia retain their power of germination
for about seventy-four hours after their discharge. In nature
the caterpillar is not visibly affected by the presence of the
fungus in its body until the afternoon of the fifth or sixth day,
when, after a brief period of nervous activity, its movements
become sluggish or cease altogether. By this time the branches
from the original germ tube have become broken up into irreg-
ular chunky “hyphal bodies,” which more or less completely
fill the body cavity. Just before death, which usually comes
toward evening, the caterpillar is almost always impelled to
climb to the highest point on the leaf or twig on which it has
been resting; the forelegs then lose their power, and the fore
part of the body droops backward or to one side in a position so
characteristic as to be easily recognized. (Plate VI.) As soon
as the caterpillar is dead, or even just before death, the hyphal
bodies within it send out stout germ tubes. (Plate VIII., Figs.
28-31.) The ultimate branches of these germ tubes break
through the integument in pustules (Plate VIII., Fig. 26),
which may eventually cover the whole body with a creamy white
mass of fungous growth, especially if the atmosphere is moist.
At the tip of each of the club-shaped branches, called conidio-
phores (Fig. 1, a, b; Plate VII., Fig. 10), a rounded bud
develops into the pear-shaped spore (Fig. 1, ¢, e), which is
shot off with considerable force when mature by a mechanism
specially developed for this purpose. Air currents may carry
the spores for miles, or if they fall on the backs of other cater-
pillars the movement of the latter may perhaps further aid in
their distribution, especially where the caterpillars are closely
congregated. The number of spores which may be discharged
from a single diseased larva is very large, probably reaching
hundreds of thousands in the case of a full-grown caterpillar,
and every spore has the power to infect another caterpillar,
provided that it strikes in a favorable position for penetration

2

under favorable conditions of moisture. It is interesting to note
that nature has provided for the wider dissemination of these
spores by impelling the dying caterpillar, as already mentioned,
to climb upward, thereby placing its body in a more elevated
position, from which the falling spores will be distributed over
a large area. In the field the dead caterpillars are found most
often on the shady under side of the limbs, near the crotches
of the branches, but one may find them with little trouble on
any part of the tree or on adjacent walls and fences. (Plate
ITI.)
Resting Spores.

Besides the type of “air spores” or ‘‘ conidia”? just de-
scribed, the fungus produces another type, formed internally,
known as “resting spores,’ which are extremely resistant to
changes of heat and cold, and which, although their germina-
tion has not been observed, undoubtedly serve to tide the fungus
over winter. They are commonly formed by the rolling to-
gether of the contents of large, irregular, fungal elements
(Plate VII., Figs. 12-18) into spherical bodies, which later
become enclosed in very thick walls. Spores of this type are
comparatively rare, and the conditions which lead to their form-
ation, whether they be due to internal causes, or to the effect of
weather, or other external influences, are not clearly under-
stood.

Encysted Hyphal Bodies.

In the fall the hyphal bodies may themselves also become
surrounded with heavy walls, which on germination split and
let out the contents in the form of stout germ tubes. (Plate
VIII., Figs. 22, 23.) The latter branch freely, and give rise
eventually to pustules (Plate VIII., Fig. 25), as in the case
of the ordinary hyphal bodies. These encysted hyphal bodies
are also instrumental in wintering over the fungus.

General Conditions governing the Artificial Spread of the Fungous
Disease of the Brown-tail Moth Caterpillar.

In the case of the brown-tail caterpillar there are two periods

in its life history when the Hntomophthora under consideration

may be effectively used, namely, in the spring and early sum-

10

mer, when the larve have left their nests to feed on the young
leaves, and in the autumn for several weeks before the webs
of the new broods are closed for the winter. During both of
these periods the rapid spread of the disease is largely depend-
ent on weather conditions, and when these conditions — warm
nights and damp atmosphere — favor the growth of the fungus,
artificial distribution yields truly satisfactory results, and may
bring about enormous and widespread destruction; but it should
be understood clearly that, even under these conditions, al-
though the disease is evidently very important as a powerful
check, it cannot be regarded as a “cure-all.” In the spring,
when the caterpillars are scattered all over the trees, it is com-
paratively easy to place the infected larvee in among them, but
in the autumn, when they are localized, feeding in the imme-
diate vicinity of the nest, it is necessary to infect individual
webs. Experience seems to point to the autumn, however, as
the more advantageous time to start the artificial epidemic.

Early Reports of the Disease among Brown-tails.

Mention has been made in previous State reports of the
occurrence of the disease in spring and fall epidemics. The
dead larve on the outside of the webs (Plate I.) were first
noticed during the early winter months + of 1902 and 1903, and
the frosty appearance of the nests, due to hundreds of thousands
of discharged spores, led to the popular belief that the young
caterpillars had been lured out of the webs by the warm mid-
day sun and had been frozen to death before they could return.
The susceptibility of the brown-tail to this disease was first
noticed by Dr. Thaxter in Maine, just after the caterpillars
made their initial appearance there. He had made a series of
experiments in artificial infection previous to the experiments
at Kittery Point, Me., in 1907, which were reported by Pro-
fessor Hitchings, and the apparent success of which led to the’
engagement of Dr. Clinton to carry on a preliminary investi-
gation in Massachusetts.

1 See Fernald and Kirkland’s Report of Brown-tail Moth Commission, 1903.

EL

Preliminary Experiments of 1908.

Dr. Clinton concluded from his preliminary experiments in
the spring of 1908 that the use of the disease as a check would
be of practical value if (1) the fungus were planted in terri-
tory where the natural disease was not in evidence, and (2) if
the plantings were made in the field before the natural disease
could develop under ordinary weather conditions, thereby giv-
ing the introduced disease an opportunity to develop more gen-
erations, and consequently infect more larve than the later-
starting natural epidemic. He was hampered in his investi-
gation by the fact that he was unable to begin operations until
the season was well advanced, and the time available was so
short that he was unable to make extensive experiments. His
results, however, again demonstrated that the propagation of
the disease in the field could be successfully accomplished.

Autumn of 1908.

Dr. Clinton being unable to continue the work after July
of this year, it was taken in charge by Mr. Speare, and the first
fall infection was made in the autumn of 1908, when about
500 diseased caterpillars were distributed over a limited area
on low shrubbery at North Andover, Mass, As nearly as could
be estimated about 35 per cent. of the young larve on the
hillside where the planting had been made died as a result of
this artificially induced epidemic.

Cultivating the Fungus through the Winter of 1908-09.

The Entomophthora from the fall infection was cultivated
and kept alive through the winter months so that the spring
planting could be made as early as possible, without the delay
incident to spring collection and forcing of the disease. In
order to accomplish this, webs were cut open and placed on a
layer of filter paper over damp moss in ordinary culture dishes.
A glass cover kept the atmosphere in the dishes moist and
favorable to the growth of the fungus. Infected larve were
placed in the cut nests, and in this manner the disease was
transmitted to the healthy larve, and the fungus kept alive
through successive generations. Some practice was necessary

12

_ before the optimum moisture conditions were determined, but
the chief difficulty encountered was the hostile action of other
fungi, which grew very rapidly under culture-dish conditions.
The worst enemy, Sporotrichum globuliferum Speg., sometimes
threatened to choke out the Hntomophthora entirely.

Spring of 1909.

The fungus having been propagated through the winter of
1908-09 at the Botanic Garden, about the first of March two
bushels of webs were brought from cold storage and placed in
two boxes, which, for the sake of convenience, will be called
the “ disease box” and the “ rearing box.” Both boxes were
of the same type, their dimensions being 11 by 27 by 27 inches,
and by leaving the bottoms open the contents were directly in
contact with the moist earth. A two-inch rim of ordinary com-
mercial tanglefoot served to keep the caterpillars confined.
Dead and dying larvze from the winter culture dishes were
turned into the disease box, together with fresh webs contain-
ing healthy caterpillars, for the purpose of starting a general
infection as soon as the latter emerged. In order to favor the
spread of this infection as much as possible the atmosphere was
kept moist by covering the box with a damp mat. Without
attempting to force the growth of the larve in either box, they
were fed just enough to keep them alive, so that the disease
might be carried along through successive generations on a
little larger scale than was possible with the culture dishes.

About April 1 larve from four bushels of cold-storage webs
were placed in five rearing boxes, and the intention was to feed
them to the limit of their capacity, so that they would be large
enough for infection and distribution by the 25th of the month.
Owing, however, to the nature of the only food which was avail-
able, the rearing of the caterpillars was attended with the great-
est difficulty, as it was almost impossible to make them feed.
Willow twigs forced under glass were not acceptable; lettuce
worked fairly well but was expensive, and the larvee did not
thrive on it, so that little or no active growth occurred until a
supply of fresh food became available out of doors as the season
advanced,

13

Feeding Methods.

The larvee were fed by two methods: (a) by placing leafy
twigs in jars sunken in the earth, or (b) by throwing small
quantities of stripped leaves directly on the clean earth. In the
first method the leaves remained fresh for some time, but in
handling the wet twigs, when changing the food or the water,
the boxes often became too damp and favorable to the growth
of the fungus, which, when once it gained a foothold, threatened
to kill off the entire supply of caterpillars. The second method
has proved to be the better for general use, because the supply
of food can be easily regulated by throwing in just enough
leaves to keep the caterpillars eating all the time. The boxes
were kept clean and sanitary by removing the dried and half-
eaten leaves as soon as the larvee crawled on fresh ones.

General Methods of Infection.

All investigators on fungous diseases of insects have experi-
enced more or less trouble in transmitting the disease to healthy
larvee in the laboratory. In most cases it seems very difficult to
imitate exactly the conditions under which the infection nat-
urally occurs. What is true of other fungous diseases is in
general true of the brown-tail disease, and it often happened
that the fungus would get a start in the rearing boxes, where it
was not wanted, and attack the larve with the virulence of an
epidemic, while in the disease boxes, where the conditions were
supposed to be at an optimum for its growth, it appeared only
in scattered spots. The three methods used for general infec-
tion may be outlined as follows: —

(a) Infection by the “ Crate Method.” — A crate 51% by 30
by 30 inches, with a mosquito netting bottom, was fitted tightly
over a second crate of similar dimensions, in which the healthy
larvee were placed. Caterpillars dying from the disease or those
already dead and ready to discharge spores were placed at
short intervals on the netting bottom of the upper box, so that
the spores from their bodies would drop through the meshes
of the netting upon the healthy larvee below.

(b) Infection by the “ Spray Method.” — Dead caterpil-

14

lars were placed in an atomizer bottle so that all of the spores
discharged would be caught on the glass. After spore dis-
charge had ceased, and the bodies of the caterpillars had been
removed, the bottle was filled with water, the spores were dis-
lodged from the sides and bottom with a soft camel’s-hair brush,
and the “spore water” was then sprayed over healthy cater-
pillars in an ordinary rearing box.

(c) Infection by the “ Natural Method.” — Infected larve
were mixed with healthy ones all over the twigs and leaves in
a rearing box. Following their natural instinct to climb, the
diseased caterpillars placed their bodies in such elevated: posi-
tions as the tips of the twigs and sides of the box just under
the rim of tanglefoot, so that the spore discharge was directed
against the bodies of the healthy caterpillars and in every direc-
tion over the leaves.

By taking lots of 100 at random fon these boxes, after they
had been exposed to the spray or spore discharge for three or
four days, placing them in small trays and counting the number
which died from the disease within nine days, it was found that
the maximum infection was hardly more than 40 per cent.?
The last method appeared to be the most favorable, and was
adopted for the infection of all of the material sent into the
field.

General Methods of Distribution.

After trying several schemes for distributing the infected
larvee it was concluded that the method first used by Dr. Clin-
ton could not be bettered for general use, because of its sim-
pheity and comparatively low cost. The method in brief is as
follows: From 20 to 30 caterpillars which had been exposed
to the spore discharge were placed in a quarter-pound paper
bag, the neck of which was wound tightly with a 10-inch strand
of No. 26 iron wire. The bag was then hung in the tree as
near the web as possible, or near the masses of feeding cater-
pillars, and its side ripped open to allow the infected larvee
to escape. In addition to this bag method, wherever it was
possible the sick caterpillars were placed directly in the feeding
masses, thus practically insuring an infection.

1 This maximum was increased by a combination of methods to 75 per cent. in 1911,

PLATE III.

Fig. 1.
FIG, 1.— Showing dead larvie on the top of an old stone wall at South Billerica.

Fig. 2.
FIG. 2.— A view of asingle stone of the above wall. All of the laryw shown are dead
from the Entomophthora disease.

15

The plantings ' of the spring of 1909 were made by the two
methods just described. In nearly every case the larve
crawled out of the bag in a few minutes, but in the first two
plantings made in late April, the cold rendered their move-
ments so sluggish that they died before they could escape. The
last three plantings were made’so late in the season that they
could not have been very effective. The season’s work proved
that artificial spread before May 1 is useless, because the irreg-
ular cold weather of late April inhibits the growth of the
fungus, and that it is extremely difficult to estimate the effec-
tiveness of plantings made after May 25 on account of the
prevalence in the field at this season of spontaneous epidemics.
In the territories of Rowley and West Newbury, where the
disease worked very successfully, the final mortalities among
the prepupez and pup ranged from 80 to 90 per cent., and in
localized: plots of intense infection it was impossible to find a
single live individual.

On May 14 the number of caterpillars dead from the disease
on the territory at North Andover, planted the previous fall,
was estimated at 50 per cent., and on May 28 at 95 per cent.
The epidemic had apparently spread about equally well in all
directions. Inspection of the estate of Mr. William Brewster at
Concord, where a natural infection had occurred in the fall,
showed that the caterpillars were practically annihilated by the
24th of May. It seemed probable that the epidemic in the
North Andover territory had been started by the diseased cater-
pillars planted there in the fall of 1908, since there was no
indication of the fungus in that locality previous to their in-
troduction, and in both eases the early appearance of the dis-
ease in the spring, and the intense destruction wrought by it,
seemed to point to the conelusion that the fungus had wintered
over in the nests, and begun its attack as soon as the young
larvee emerged.

Autumn of 1909.
In the autumn of 1909, the supply of webs in cold storage
being insufficient, only three plantings were made, two of which
were effective in killing off 20 to 30 per cent. of the larvae, thus

1 See page 26 for list of localities planted.

16

confirming the results of the preceding fall; the other was
spoiled for observation because the infected webs were cut
from the trees and burned by the owner of the property.

Spring of 1910.

The fungus was carried over the winter of 1909-10 in cul-
ture dishes by the method already outlined, and a general infec-
tion started in the disease boxes in the usual manner. A disas-
trous epidemic of Sporotrichum globuliferum Speg., which
killed off a large number of the larve and threatened to choke
out the Entomophthora altogether, was controlled only with the
greatest difficulty. In spite of this hindrance, however, a suffi-
cient quantity of infected material was ready for planting on
the 1st of May. The diseased caterpillars were distributed over
a solid block of territory about twelve square miles in extent,
running along the railroad track from Ipswich to within one
mile of the New Hampshire line, and also in six scattered
plantings on private estates. Weather conditions were favor-
able, and regular inspection at intervals during late May and
early June revealed a mortality estimated at about 35 per cent.,
with the disease universally distributed through the planted
areas. The virulence of the epidemic gradually increased until
the larvee began to spin up, about the middle of June, when
the per cent. of those visibly affected rose so high that only 80
out of 1,000 pupe and prepupe collected from all over the
planted territory matured moths.

It might be stated here that the word per cent. as used above
should not be taken in its literal sense, as it is impossible to
arrive at an absolutely correct determination of the work of the
fungus at any given moment. The reasons are obvious. Only
those caterpillars visibly affected with the disease at the time
of inspection ean be used in the calculation, which means that all
larvee which have died and dropped from the trees, as well as
those infected but not yet dead, must be inevitably overlooked.
Moreover, at the time of inspection the disease may be at a
very low ebb, due to adverse weather conditions or some other
cause, and the inspector will get the impression that the fungus
is not working at all. Territories in which the disease ap-

17

peared to be working to perfection in May often exhibit only
scattering evidence of the destruction wrought when inspected
in June, and in other territories the June death rate may be
the highest of the season. Since the conditions in the field are
so variable, careful inspections and estimates must be made at
intervals throughout the entire season in order to arrive at
even an approximate estimation of the total work that the
fungus has done.
Autumn of 1910.
Seventy bushels of webs were brought from cold-storage on
the 25th of July to furnish the larve for the fall infection of
this year. The caterpillars were placed in long rearing boxes
out of doors under favorable conditions for their growth, but
an attack of the disease, which started from one box in which
there must have been a few infected webs, and spread rapidly
to all of the others, killed off 90 to 95 per cent. before the
20th of August. The few that survived were evenly distributed
in five disease boxes, and with them were mixed healthy larvee
from the webs in the field. Although this meager supply of
diseased material was unsatisfactory, about forty plantings
were made, with the co-operation of the State agents and super-
intendents, on low shrubbery in eastern Massachusetts. A new
method of sending the caterpillars to the field, in mailing cases,
was tried in connection with these plantings, and proved to be
satisfactory, except in those instances where the cases were
delayed in the mails until the larvee were dead when they
arrived at their destination. In making the plantings all the
nests that could be conveniently reached were ripped open, so
that a few of the infected caterpillars could be inserted directly
among the healthy occupants. The bag method was also used
successfully. Where the contour of the country permitted, the
plantings were made at 50-foot intervals, and the whole planted
territory divided into plots of convenient size for careful ob-
servation. A count of all of the nests in a selected plot was
recorded at the time of planting, so that the spread of the dis-
ease might be checked up at each inspection. The reports of
the inspectors showed that the disease became evident after
ten days in every plot, and that the number of dead larvee on

18

the outside of the nests increased very rapidly, first in the
immediate vicinity of the infected web, and then in scattered
spots all over the territory. The following typical report from
two inspections of a planting made August 13 at Clinton gives
some idea of the rapid death rate. One bag, containing 15 to
20 diseased caterpillars, was hung in the middle of each plot,
and the plots so chosen that the bags were about 50 feet apart.

Prom, | at | Infested | Deel Earrs | tutectad | eed
Webs in Plot. | September 10. September 15.
Pig wate 12 4 67 10 931
a Sie ae 10 3 46 9 340
PH we ete 23 6 149 15 410
TVali rah ate 20 6 78 13 177

The area of each plot was between 400 to 500 square feet. The
same results were reported from the other plantings, which
were practically all successful, resulting in the infection of 35,
to 50 per cent. of the webs in the planted areas.

Spring of 1911.’

Following the same general methods in rearing, infecting
and distributing the caterpillars used in previous experiments,
the work of the spring of 1911 was continued on a still larger
scale. The only change in the rearing and disease boxes was
the use of heavy wire screening with a quarter-inch mesh on
the bottoms, to retain a thin layer of earth and prevent the
escape of the larvee whenever the boxes had to be moved. The
late spring, and consequent late opening of the foliage, made
the work of early rearing very difficult, and it was necessary to
draw on a supply of raspberry leaves, grown in the greenhouse
and intended for use in raising gypsy larvee, until the willow
and cherry trees came out. Beside the extensive plantings
made by two men employed especially for the purpose during
the month of May, a general distribution of infected caterpil-
lars was made possible with the help of the State agents. Ship-

1 Mr. Colley took full charge of the work in February, 1911.

PLATE IV.

Fig. 1.
Fic. 1.—Long rearing boxes under the trees at the Botanic Garden, used to force the
larvee for the infection experiments of the fall of 1910,

= :
Fig. 2.
Fic. 2.— Rearing boxes protected by cotton drilling to prevent the spread of an epi-
demic of the disease in the fall of 1910. It was thought that the cotton cloth would
stop spores from being blown in from the infected boxes,

19

ments were made also to interested persons all over the State
for private experiment, as long as the material lasted.

The extreme dryness of the month of May hindered the
growth of the fungus to a very large extent, so that the final
results were not as good as those of the preceding spring, but
toward the end of the season there was a general infection all
over the planted territory. In and around Ayer the number °
of caterpillars visibly affected with the disease on the 27th of
June was estimated at 60 to 70 per cent., and the trees in
-which the fungus had been planted were not nearly so badly
stripped as those in which the caterpillars had been unmo-
lested. In contrast to this condition a badly infested scrub
growth of oak and cherry in Roberts, where no fungus had
been planted, was completely defoliated, and the natural dis-
ease, though evident on one or two bushes, was not present in
epidemic form.

Early inspection of the plantings made in the autumn of
1910 showed that the infection was general, but was not spread-
ing far from the planted areas, except in one or two instances.
In spite of this fact the defoliation in these areas was notice-
ably less than in areas where no fungus had been distributed.
As in the spring of 1910, the death rate after the 15th of June
increased very rapidly, and in Georgetown, where an excellent
infection was started the previous September, the caterpillars
in the planted territories were almost completely annihilated.
The territory between Ipswich and Rowley, which is damp
nearly all the time, on account of the proximity of the ocean
and salt marshes, was found to be practically cleared of brown-
tails by the disease,

Autumn of 1911.

In preparation for the fall infection the larvee were brought
from cold storage on the 15th of August, three weeks later
than in previous seasons, and fed wholly on cherry. Fortu-
nately, the disastrous results which attended our efforts to force
the caterpillars in July and August, 1910, were not repeated,
so that ten bushels of webs furnished an abundant supply of
larvee about one-half inch long by the 1st of September. It
was found advisable to cover the bottoms of the rearing boxes

20

with a thin layer of coarse gravel, which was a great aid in
keeping the boxes clean. Two disease boxes had been run all
summer, and from them infection was started in seven others.
The latter were all arranged as shown in Fig. 2, and by a com-

bination of the ‘

‘natural method” and the “ spray method ”

a comparatively high per cent. of infection was obtained. The
* following table shows the results obtained in five test experi-
ments. In each case the caterpillars were picked at random
from the disease boxes and packed in mailing cases for several
hours, as if they were to be shipped to agents in the field, to
imitate the normal conditions of distribution, before being

placed in the observation trays.

Trays. i aeaeed in Larieie anne Appronmnaye
Tray. Nine Days.
i : - - : 2 6 180 97 53
MMe . q : : : c . 253 204 80
Ds. : c : : : C 219 183 83
Vie ses 2 0 C : : > 144 109 75
Win 129 97 75

Planting was commenced on the 1st of September and ended
on the 12th, during which time approximately 100,000 cater-
pillars were distributed, a great increase over the number dis-
tributed in the fall of 1910. The caterpillars, packed in mail-
ing cases as before, were delivered by automobile, a method
which assured their reaching the agents in good condition, be-
cause by its use unnecessary delay in transit was avoided.
With one or two exceptions all of the infected caterpillars were

planted directly in the nests.

About the middle of October an inspection of all the nests on
plotted areas in plantings in Waltham, Stow, Marlborough and
Hudson showed a general infection, about half of the nests
examined being diseased.t In all of this autumn’s work only
three cases of naturally infected webs were observed, a fact
which led to the conclusion that the epidemic in these areas

1 The number diseased was 763 out of 1,628, by actual count.

24

was due to the infection started by the introduced caterpillars.
There is every indication that, with favorable weather condi-
tions, the work of the fungus will be evidenced in the spring of
1912 by a more or less complete annihilation of the brown-tails
in and around the territories where the plantings were made
this last autumn.

In summing up the results of the investigations covering the
four seasons 1908-11, it may be said that it has been found
possible to propagate the disease in the laboratory, and to infect
caterpillars in the field successfully, both in the spring and in
the fall. Under favorable weather conditions the artificially
induced spring epidemics have resulted in many cases in the
practically complete destruction of the larve in the planted
areas. In the fall epidemics the number of nests infected at
the end of the season has ranged from 30 to 50 per cent., and
these nesfs have apparently formed the starting point of early
spring infections. The fall plantings have, therefore, a two-
fold efficiency, in that they not only result in the destruction
of one-third to one-half of the caterpillars in the autumn, while
they are small and comparatively harmless, but also, by es-
tablishing the disease in the nests, enable an epidemic to get
started much earlier in the spring than any natural infection
could develop under ordinary weather conditions. The last
three or four years have not been particularly favorable for
natural epidemics or for furthering the spread of the intro-
duced disease, and it seems reasonable to suppose that the fun-
gus would have been far more effective if the weather, espe-
cially during the spring months, had been warmer, with a
larger rainfall. It has, of course, been impossible to plant all
of the infested territory with diseased caterpillars, and in many
cases areas cleared of brown-tails by the fungus in the spring
have been invaded by moths from uninfected localities, with
the result that they were infested as badly as ever in August.
This condition of affairs is unavoidable, since we are dealing
with a moth that may fly, or be blown, for some distance, and
it is therefore impossible to guarantee that the fungus will
clear any territory of moths so that it will remain free for
any length of time. The presence of the disease does not ren-

22

der a territory immune to future immigrations, but it certainly
will reduce the amount of damage that the invading moths
may do. The determination of the distance to which the dis-
ease may spread is extremely difficult. Undoubtedly the spores
are often blown for miles, and in such cases the epidemic
might jump from one territory to another widely separated
from it, but there would be no means of telling just where the
spore or spores which started the second epidemic came from.
As can be seen from the table on page 18, one bag of 20 to 30
diseased caterpillars is sufficient to infect an area of approxi-
mately 625 square feet ; any further spread of the disease would
be variable, and dependent upon weather conditions,

Webs in Cold Storage.

Before giving general directions for private experiment it
seems advisable to mention the advantages of having a supply
of webs in a cold-storage warehouse, or packed in a dry box in
an icehouse where the temperature does not go over 35 degrees,
to furnish the proper amount of material at short notice for
spring or fall work. It is difficult to collect larve just when
they are needed in the spring, for the caterpillars have usually
started to feed, and it is impossible to collect them in the sum-
mer in time for the fall work, for they do not emerge from
their eggs until the middle of August. Care should be taken
that such webs as are selected for this cold-storage supply are
not infected with the disease at the time of collection, for if
they are it will become epidemic when the nests are brought
out into the warmer air, and completely destroy the larve in
the rearing boxes.

Directions for Private Experiment.

With such a supply of webs to draw from, persons wishing to
make private experiments might proceed something as fol-
lows : —

Two boxes should be constructed after the manner shown in
Fig. 2, and set in two frames (Plate V., Fig. 2) some distance
apart, one for rearing the caterpillars and one for forcing the
disease. The bottoms of both boxes should be covered with a

PLATE V.

Fig. 1.
FIG. 1.—Showing the proper method of
hanging the bag containing the infected
caterpillars close to the nest.

Fig. 2.

Fic. 2.— A cheap but eflicient frame and disease box for private experiment.

-
-
=
eI
=)

23

thin layer of gravel. About April 1, 200 stored or freshly
cut webs should be placed in each box, and in addition to this
number the box chosen for the disease box should also receive
two or three dozen infected webs from some locality where the
disease is known to be present.

Fic. 2.— Diagrammatic view of the interior of a rearing or disease box. Forked sticks bbb
driven into the ground support crosspieces cc, on which leafy twigs may be hung. Other
leaves should be scattered on the ground beneath the crosspieces. Infected caterpillars will
usually crawl up the forked sticks and along these crosspieces, so that the spores from their
bodies will fall on the healthy larve feeding below. A two-inch rim of tanglefoot in the
position indicated by aa will keep the caterpillars confined.

In the matter of food, sanitation, heat and shade experience
is the only reliable guide, but in general, young buds, stripped
from oak or cherry trees, make the best material for early feed-
ing; the boxes, especially the rearing box, should be kept as
clean as possible, and the shade should be arranged so that the
temperature does not go much over 80 degrees. The disease
box should be kept dark and moist most of the time by covering
with a damp mat, but here again the rule is not without excep-

24

tion. The rim of tanglefoot, indicated in Fig. 2, should be
frequently combed,

After about ten days, by which time the disease should have
made its appearance, the disease box should receive constant
attention. ach night and morning the dead and dying cater-
pillars should be evenly distributed among the other larve in
the box, in order to make the infection as general as possible.
The ‘spray method ” outlined on page 13 should be used in
conjunction with this “natural method.” Furthermore, it is
particularly important, in the attempt to hasten the general
infection, that the number of larve in the disease box should
be kept nearly constant, by transferring healthy caterpillars
from the rearing box to replace those killed by the disease.
Broad-pointed forceps should be used in handling the ecater-
pillars.

Planting should be commenced about the first of May, and
can be continued to advantage until the first of June. Twenty
to 30 of the caterpillars which have been exposed to the spore
discharge in the disease box should be placed in a quarter-
pound paper bag, the neck of which should then be tightly
wired with a convenient strand of No. 26 iron wire, or other
suitable material. The bag, when it has been hung as near as
possible to the masses of feeding larve or to the nests (Plate
V., Fig. 1), should be ripped open to allow the escape of the
infected caterpillars.

For successful autumn planting a supply of cold-storage webs
is absolutely necessary, because the fungus must be kept alive
through successive generations during the summer months in
the disease box, and to do this one must have a few webs on
hand all the time. Moreover, as stated before, the larve in
the field are not large enough for convenient handling in the
fall experiments. The rules given for spring rearing and in-
fection hold in general for the autumn work, except that it is
not necessary to keep the boxes under glass. Autumn planting
should be direct, that is, infected caterpillars should be placed
directly into nests conveniently reached, a method which insures
an infection and which is simpler than the bag method. Pliable
branches may be pulled down with a hooked pole. Where there
are a number of nests on a small bush the central nest may be

29

directly inoculated and the surrounding nests tied up to it with
a piece of heavy cord, which may be cut at the first inspection,
after the infection has spread. Another method, devised by
Dr. Thaxter, is as follows: cut, infect and bind together half a
dozen or more nests. To one end of a string of convenient
length attach a small stone, throw the stone over the infested
tree and pull the bunch of webs attached to the other end of the
string up into the topmost branches, where the nests are usually
crowded and the infection will do most good. All of these sug-
gestions can be varied to suit conditions of moisture, contour
and shrubbery on the territory which is to be planted. Where
it is convenient the nests which have been cut from fruit trees
may be piled in an open field or in swampy pasture land and
the infection started in the pile. Such a method will result
in the practically complete destruction of the caterpillars, will
allow the escape of insect parasites which would be killed by
burning, and will establish the starting point for an epidemic
which should spread to the surrounding bushes and trees. It
has been found advantageous in some cases to burlap the trees
in which the fungus has been planted, especially in the spring,
as the caterpillars, in crowding together under the burlap,
easily transmit the disease to one another.

Conclusions.

The artificial propagation and use of the brown-tail fungus
has been clearly shown to be an effective means of destroying
the caterpillars of this insect in great numbers and over con-
siderable areas,

Although the success of this artificial use is variable, owing
to the fact that the degree of warmth and moisture most favor-
able for the growth of the fungus, and dependent on weather
conditions, cannot be controlled, the introduced disease can in
general be depended on to kill from 60 to 100 per cent. of the
caterpillars in the planted areas.

Plantings of the infected caterpillars should be made prefer-
ably in localities where the natural disease is not known to be
present, in the spring from May 1 to June 1, and in the autumn
from August 25 to September 10.

The fungus usually lives over winter from the autumn infec-

26

tion, and does effective work, as is evidenced by the early
appearance of the disease and the reduction of the spring defo-.
liation in localities where it was introduced the preceding fall,
and for this reason fall infection is doubly effective.

Artificial distribution is most easily accomplished in sprout
woodlands and pastures where the ordinary methods of control.
such as spraying and cutting, are not employed, and where
the nests are more readily accessible.

List of Localities where the Fungus has been planted.

Spring, 1908.— Concord, Gerrish Island, Me., South Billerica, State
Line, Waltham.

Fall, 1908. — North Andover.

Spring, 1909.— Ballardvale, Chelmsford, Concord, Lowell Junetion,
Newburyport, North Andover, North Wilmington, Rowley, Salis-
bury, West Newbury, Woburn.

Fall, 1909. — Mishawum, North Wilmington, Newbury.

Spring, 1910. — Territory along railroad track from Ipswich to New
Hampshire line. Seattered plantings on six private estates.

Fall, 1910.— Amesbury, Andover, Billerica, Bolton, Boston, Boxford,
Clinton, Cohasset, Dracut, Georgetown, Groveland, Fitchburg,
Framingham, Harvard, Leominster, Lunenburg, Medfield, Methuen,
Newbury, North Andover, Reading, Rowley, Scituate, Shirley,
Tewksbury, West Newbury, Worcester.

Spring, 1911.— Intensive planting in and around Ayer. Dunstable,
Groton, Leominster, Lunenburg, Pepperell, Paes Stony Brook,
Westford, Whalom.

Fall, 1911. — Amesbury, Arlington, Ashland, Bedford, Belmont, Berlin,
Boxford, Burlington, Carlisle, Coneord, Danvers, Dedham, Dover,
Fayville Dam, Framingham, Georgetown, Groveland, Hamilton,
Hopkinton, Hudson, Ipswich, Lakeside, Lexington, Lincoln, Lynn,
Marlborough, Malden, Melrose, Merrimac, Needham, Northborough,
North Reading, Newbury, Roberts, Salisbury, Saugus, South Acton,
Southborough, Stoneham, Swampscott, Wakefield, Waltham, Wel-
lesley, Weston, West Acton, West Newbury, Wilmington, Win-
chester, Woburn.

This list indicates the localities where the fungus has been
planted, but not the number of plantings. In many instances
several plantings were made in the same town.

27

List of Hosts of Entomophthora Aulice Reich. reported in the United
States. Hosts of Hmpusa grylli Fres. are excluded.

Agrotis sp., eutworm, . : P ; ; : . Thaxter.*
Catocala sp., : : : ‘ . Clinton.
Estigmene acraea, a ae cutee ; : . Clinton.

Euproctis chrysorrhoea, brown-tail moth eaterpillar, Kirkland, Stone
and others.”

Hyphantria textor, fall webworm, . : : a Pheer.
Lithophane (Xylina), cutworm, . ; ; F 2) Thaxters
Malacosoma americana, tent caterpillar, . ‘ . Clinton.

Mamestra sp., cutworm, . : ; , 2. Uhaxters
Orgyia nova, rusty tussock moti : : : 7) chaxten
Phlegethontius carolina, tomato worm, ‘ : . Thaxter.*
Phlegethontius celeus, tomato worm, . f 3 . Thaxter.*
Pyrrharctia isabella, Isabella moth, . . : «/ Thaxter.*

{ Thaxter.*
"| Webster.*
Eucheies Egle, . : ; : ‘ ; : . Thaxter, herb.
Smerinthus modestus, . 4 f l ‘ : . Thaxter, herb.
Amphipyra pyramidoides, . : : . Thaxter, herb.
Larva of diurnal lepidoptera, adeibabie Panessa . Thaxter, herb.
Larva of diurnal lepidoptera, sp.,_. : 2 . Thaxter, herb.

Spilosoma virginica, yellow bear,

1 Ann. Rept. Connecticut Agri. Exp. Sta., 1890; 95, 1891.

2 Ann. Rept. Mass. Supt. Suppression of Gypsy and Brown-tail Moths, 1, 130, 1996.
3 Mem. Boston Soc. Nat. History, IV.; 159-162, 1888.

4 Journal Cincinnati Soc. Nat. History, XVI.; 175, 1894.

EXPERIMENTS WITH THE GYPSY FUNGUS.

In the spring of 1908, while Dr. Clinton was carrying on
preliminary experiments with the brown-tail fungus, he re-
ceived from the Melrose laboratory specimens of Japanese
gypsy larvee, shipped from Japan with other material, which
had been killed by the attack of an Hntomophthora, but owing
to the fact that the caterpillars had been dead for some weeks,
all attempts to make this fungus develop its spores were unsuc-
cessful. As it was thought that this species of Hntomophthora
might be as effective in destroying the gypsy larve as Hnto-
mophthora Aulice was in destroying the brown-tail, Dr. Clin-
ton, through the generosity of a friend of Harvard University,
was sent to Japan to obtain the living fungus, and after great
difficulties succeeded in bringing a few infected Japanese cater-

2S.

pillars to Cambridge. Of the few larvee which survived the
long trip and severe heat only two developed the disease.
These two were put immediately into a moist culture dish,
so arranged that the spores would be discharged on healthy
caterpillars. Only one of the latter developed typical conidia,
but the growth was so feeble that probably very few spores were
discharged. The pustules of conidiophores and attached spores
were picked off and transferred directly to healthy caterpillars.
and the dead bodies of the few larvee which had developed rest-
ing spores were carefully saved. The caterpillars directly inoe-
ulated showed signs of the disease externally on the eighth day |
after infection, but in no case was the appearance typical.
From this generation of the fungus 30 caterpillars were inoc-
ulated directly as above, and by successive transfers the num-
ber which developed the conidial form of the disease was
increased steadily, though slowly. Resting spores were gen-
erally formed with the conidia. By the time the disease was
running well in the infection boxes the larve in the field had
practically all become prepupz or pup, and since the attempt
to raise caterpillars from cold-storage eggs was unsuccessful, the
disease, from lack of hosts on which it could be propagated,
died out late in August.

Healthy gypsy larvee were put into the infection box of the
previous spring on May 15, 1910, and the disease, which de-
veloped spontaneously on the 2d of June, was kept running
until the last of August. Reinfection was undoubtedly accom-
plished through the germination of some of the thousands of
resting spores, formed during the previous season, which were
lying on the bottom of the box. From June 15 to July 2 six
plantings were made, following the same methods used suc-
cessfully with the brown-tail fungus, in Billerica, Brookline,
Lynn, Saugus and North Wilmington, but regular and careful
inspection of these plantings revealed neither the conidial nor
the more common resting-spore stage of the fungus.

In the spring of 1911 the same plantings were inspected
carefully to see whether the disease had possibly started as a
result of the infection made in 1910, but no indication of its
presence was discovered. The disease boxes at the garden had
not been disturbed during the winter, so they contained all the

PLATE VI.

Gypsy caterpillars dead from a disease similar to the brown-tail fungus. Note the
characteristic position of the body of the dead caterpillars.

29

resting spores formed in 1909 and 1910, except those which
must have germinated and the few removed for experiment
and examination. The disease appeared on the 23d of May,
when a very small larva broke out with a few feebly growing
pustules. On the 27th a half-grown caterpillar died from the
disease in the greenhouse, and again on the 9th of June a large
gypsy was found rigid and ready to shoot. From these larve,
and from others which subsequently developed the disease,
about 500 caterpillars were directly inoculated, but it was not
until the 19th of June that the supply of diseased material
warranted the first planting, at Brookline. On the 24th and
26th of June two other plantings were made in a badly infested
scrub oak woodland in Roberts. Careful inspection on the
29th of June, and on the 6th and 15th of July, failed to reveal
the slightest sign of the fungus in either of these plantings.
The wilt disease appeared to be universally distributed wher-
ever the gypsies were feeding, and was severe enough during
the hot weather of the last half of June and of early July to
kill off the caterpillars in the rearing boxes and the disease
boxes at the garden to such an extent that the propagation of
the fungus became more and more difficult, until finally it had
to be abandoned, owing to the total destruction of the culture
larve,
Conclusions from work on the Gypsy Fungus.

The experiments with the gypsy fungus, notwithstanding
the fact that they were made under unfavorable weather condi-
tions, both in 1910 and 1911, indicate that this disease is not
a promising form for artificial use. This conclusion is based
not only on the fact that the fungus is itself far more difficult
to propagate than that of the brown-tail, and is much more sen-
sitive to unfavorable weather conditions, but is also evident
from the fact that the breeding in confinement of gypsy larve
is associated with difficulties which are in themselves sufficient
to render the continuous propagation of the fungus from month
to month or from year to year almost impossible.

Should it obtain a foothold in the field, however, it might be
expected to prove continuously effective from season to season,
owing to its habit of forming resting spores in great abundance,
which the experiments have shown are able to survive the New

30

England winter, and a very slight increase in virulence, such as
often appears in parasitic fungi in successive seasons, might
bring about quite different results from those above reported.

LITERATURE.

Among some of the more important articles dealing with
insect diseases and their practical use the following may be
mentioned : —

1855. Conn, F. Empusa musce und die Krankheit der Stubenfliegen.
Nova Acta Acad. Caes. Leop. Carol. d. Nat., XXV., 301,
1855.

1869. ReicHarpt. Empusa Aulice. In Bail, Ueber Pilzepizootien in
Schriften d. Natur. Ges. Danzig. N. F. Band II., 3, 1869.

1875. Conn, F. Entomephthora Aulice. Beit. z. Biol. d. Pflanzen,
Band I., Heft VII., 1875. ;

1882. Nowaxowsk1, L. Entomophthoracee. Report in Bot. Zeit.,
1882, 560.

1888. THAxTeR, R. The Entomophthoree of the United States. Mem.
Boston Soe. Nat. Hist., 4, 133-201, 1888.

Forses, 8. A. On the Present State of our Knowledge concern-
ing Contagious Insect Diseases. Psyche, Vol. V., 3, January—
February, 1888.

1889. Grarp, A. Review of Krassiltschik’s “ De Insectorum Morbis
qui Fungis Parasiticis Efficiuntur.” Bul. Sci. de France et de
la Belgique, Tome XX., 120-136, 1889.

Snow, F. H. Experiments on Artificial Dissemination of Con-
tagious Diseases among Chinch Bugs. Kansas Academy of
Sciences, Vol. XITI., Topeka, 1889.

1892. Burtsson, M. Le Botrytis tenella. Nouveau Moyen de détruire
les Vers Blanes et les Hannetons. Compiegne, Imprimerie
Henry Lefebvre, 31 Rue Solferino, 1892.

1893. Grarp, A. L’Isaria densa. Bul. Sci. de la France et de la Bel-
gique, Tome XXIV., 1893.

1895. Prerrit, R. H. Studies in Artificial Cultures of Entomogenous
Fungi. Bul. 97, Cornell University Agri. Exp. Sta., 1895.

1897. Routrs, P. H. A Fungous Disease of the San José Seale, Sphe-
rostilbe coccophila Tul., Bul. 41, Florida Agri. Exp. Sta., 1897.

1901. Danysz, M. J., and Wizz, M le Dr. K. De L/utilisation des
Muscardine dans lia Lutte avee le Cleonus punctiventris.
Libraire Agricole de la Maison Rustique. 26 Rue Jacob,
Paris, 1901.

Howarp, L. O. Experimental Work with Fungous Diseases of
Grasshoppers. U.S. Dept. Agri. Yearbook, 459, 1901.

1902.

£903.

1906.

1908.

1909.

1910.

eo.

ol

Brunner, L. Killing Destructive Locusts with Fungous Diseases.
U. 8. Dept. Agri., Div. of Entomology, Bul. 38, new series,
1902.

Suetpon, J. L. Cultures of Empusa. Journal of Applied
Microscopy and Laboratory Methods, Vol. VI., No. 3, 2212-
2220, Rochester, N. Y., 1903.

Outve, E. W. Cytological Studies on the Entomophthoree.
Bot. Gaz. 41, 192-208, 229-261, 1906.

Rippiz, L. W. Cytology of the Entomophthoracee. American
Acad, Arts and Sciences, 42, 10, 1906.

Rours, P. H., and Fawcert, H. 8. Fungous Diseases of Seale
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Hircuines, Professor. Note on the Infection Experiment at
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Spraying with Aschersonia. Florida Agri. Exp. Sta. Report

for year ending June 30, 1909, 38-41; 1910, 39.

Bercer, E. W. White-fly Control. Bul. 103, University of
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Explanation of Plate VII.

Fics, 1-4.— Typical conidia.

FieGs. 5-7.— Germinating conidia.

Fic, 8.—Secondary conidium produced directly from a primary conidium.

Fic. 9, — Four small hyphal bodies.

F1G. 10.— Group of conidiophores showing four stages, a, b, c and d, in the development
of the conidium.

Fig. 11.— An abnormal hyphal body, apparently partially encysted.

FIGS. 12-17.—Characteristic forms of hyphal bodies prior to and during the formation
of resting spores.

Fig. 18.— A mature resting spore.

Fig. 19.—Section through the body of a caterpillar, showing the relation of the conid-
iophores to the integument.

PLATE VII.

Explanation of Plate VIII.

FIGs. 20-21.—Encysted hyphal bodies (autumn), ’

FIGS, 22-23.— Germination of the encysted hyphal bodies.

Fic. 24.— A conidiophore, showing the old walls of primary, secondary and tertiary
conidia which have germinated in situ.

FIG. 25.— Pustule of conidiophores which developed from germinating encysted hyphal
bodies in a culture dish in the laboratory.

FIG. 26.— Section view of a similar pustule breaking through the integument.

FIG. 27.— Formation of a conidium from the germination of an encysted hyphal body.

FIGs, 28-31.— Germination of the ordinary type of hyphal bodies.

Fic. 32.— A germinating conidium showing the cross septa a@ which closes the empty tube
after the advancing protoplasm.

Fic. 33.— An abnormally large hyphal body.

Allthe figures were drawn with the aid of the camera lucida, and are reduced about
one-third in reproduction. With the exception of Figs. 19, 25, 26 and 27 the magnification
was approximately 425; for Fig. 19 the magnification was about 90; for Figs. 25 and 26,
about 300 ; and for Fig. 27, about 600.

PLATE VIII.

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