Article beginning on page 225.
Psyche 6:225-232, 1891.

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PSYCHE.
EXPERIMENTS FOR THE DESTRUCTION OF CHINCH BUGS BY INFECTION.
BY FRANCIS H.. SNOW, LAWRENCE, KAXSAS.
[Annual address of the retiring president ofthe Cambridge Entomological Club, IZ February, 1S9a.l I regret my inability to be present at
the annual meeting of the Club on the
8th inst.* I, however, forward the fol-
lowing account of my experiments for
the destruction of chinch bugs in the
field by the artificial introduction of
contagious diseases. This may serve
as my annual address as president of
the Club. One of your former presi-
dents, Prof. S. A. Fosbes of Illinois,
adopted a similar subject for his annual address.
At the outset, I desise to call your
attention to the difference between my
own experiments and those of Prof.
Forbes. The latter has been working
for several years in the line of commun- icating contagious diseases to chinch
bugs by means of artificial 'cultures uf the microscopic plants which produce
disease. He has not, however, th~ls
far, been successful in communicating
disease to chinch bugs in the fields by
means of artificial cultures. In my
own experiments, continued now for
three years, I have proceeded upon a
different basis. Recognizing the failure of previous attempts to destroy chinch
The address reached the Club too late for the meet- ing of S January.
bugs by the application of artificial cul- tures of disease germs, I conceived a
very simple idea of making the chinch
bug himself the vehicle for the commu-
nication of disease in the field.
Dr. Otto Lugger of the Minnesota
Agricultural Experiment Station in the
autumn of 1888 distributed in certain
fields infested with chinch bugs the
dead bodies of bugs that had died in
other fields from disease which was
naturally present. Dr. Lugger, how-
ever, was in doubt as to whether disease was actually communicated in the field
by these dead b~igs, thinking that per-
haps the disease after all might have
reached the fields in which he distrib-
uted his material by the natural progress of the disease from field to field. So
far as I know, Dr. ~u&er did not fur-
ther continue these experiments, and
made no investigations in the labora-
tory with reference to preserving the
infection through the winter and exper-
imenting in the following season with
infection thus preserved.
In June, 1889, I obtained the first
material for my experiments from a
farm in Morris County, Kansas. This
material consisted of Empusa, deter-




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[March 1l?92.-
mined as E?apasa a$hidis by Dr.
Thaxter, and do~~btless identical with
the Entomophthora of Prof. Forbes's
presidential address.
With this material I was able to test
my theoi-y that chinch bugs from the field having been made sick by contact with
the dead bodies of bugs killed by dis-
ease in the laboratory, if turned loose in the field would communicate the disease
to the field bugs. I found that in the lab- oratoi-j- exposure of healthy bugs to bugs dead from disease, was invariably fol-
lowed by the death of the exposed bugs
in from eight to twelve days. A simi-
lar operation in the field led to the same result.
I have thus experimented with all
three diseases now known as fatal to
chinch bugs : - the S$o~ot~ichum
gZo6uZ{fe~u?n of Spegazzini which I
have called the 'bwhite fung~~s" dis-
ease : the Em?usa a9hidis of Hoffman
which 1 have called the 6igray fungus"
disease ; and the Mic~ococcus insecto-
Y Z ~ of Busrill, which is a bacterial dis- ease. The S$o~otrichum gZo6uZz'fe~um
(thus detei-mined by Dr. Thaxter) is
identical with Botrytis referred to by
Prof. Forhes in his address.
I have been able to keep two of these
diseases alive through two successive
winters in my laboratory, and have been
able to supply farmers with infection
upon demand in the following season.
My experiments have shown that the
two fungus diseases, Sporotrichum and
Emp~~sa, are more destructive in damp
weather than in dry, while the bacterial disease (Micrococcus) is most destruc-
tive in hot, dry weather ; thus in 1890, which was a very dry year in Kansas,
the crops being seriously injured by
drouth in all pasts of the State, the
fungus diseases had very little effect in the destruction of the chinch bug, while the bacterial disease was exceedingly
destructive. During the year 1891,
which was a wet year in Kansas LIP to
the end of July, the fungus diseases
sent out from my laboratory again re-
sumed their destructive effect in the
fields ; the bacterial disease becoming
most destructive after the close of the
wet weather in July.
Considerable prominence having
been given to the subject of my experi-
ments during the year I 890, the legisla- ture of Kansas in February, 1891, made
a special appropriation of $3,500 to
enable me to. continue my investigations upon a larger scale than had previously
been possible. By means of this ap-
propriation I have been able to equip a
bacteriological laboratory and obtain
the apparatus necessary for thorough
study of the subject. I have also been
able to propagate infection upon a large scale, in order to meet the lai-ge de-
mand from the farmers of Kansas and
other States for infected chinch bugs.
During the year 1891 infection has
been furnished to about 2,000 farmers,
chiefly in Kansas, b ~ ~ t also including all the western States exposed to the rav-
ages of the chinch bug. I have re-
ceived I ,390 reports from farmers stat- ing the results of their experiments. Of these field experiments I ,050 have been successful, 187 unsuccessf~~l, and I 53




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doubtful.
Stated in another form 75.6
per cent of the experiments have been
s~iccessful ; 13.4 per cent unsuccessful ; and 11 per cent doubtful. These
field experiments have been dis-
tributed among the various States as
follows : Kansas, I ,222, (successf~d,
953, uns~~ccessf~~l, 140, do~~btful, I 29) ; Illinois, 40, (successfu1, I 7, unsuccess- ful, IS, doubtful, 8) ; Texas, 26, (suc- cessful, 13, ~~nsuccessful, 6, doubtful, 7) ; Wisconsin, 29, (successful, 13, un- successfu1, 13, doubtful, 3) ; Oklahoma
Territory, 26, (successful, 20, unsuc-
cessful, 4, doubtful, 2) ; Missouri, 13, (successful, I I, unsuccessful, 2) ; Iowa, 15, (successful, 9, unsuccessful, 5,
doubtful, x ) ; Minnesota, 8, (successful, 3, ~msuccessful, 2, doubtful, 3) ; Indian Territory, 2, (successful, 2) ; Nebraska, 6, (successf~il, 6) ; Indiana, I, (success- ful) ; Arkansas, I, (successful) ; Miss- issippi, I, (successfu1).
In order to assure myself of the actual
condition of the experiments in the field, I have personally visited a large num-
ber of fields during the past season
while the experinlents were being per-
formed, and have kept a field agent con- stantly in the field during a large part of the time. He has made a thorough
examination of eighteen Kansas coun-
ties and has assisted me materially
in determining the true character of the field experiments, corroborating in a
great majority of instances the reports
of the farmers as to the working of the
infection in their fields.
In this address I cannot enter exten-
sively into the subject of these experi- ments, but will give a brief statement
of the principal points connected with
tlie laboratory work with each of the
two fung~~s diseases.
On May 23d we began our experi-
ments with Sporotrichu~n. We dis-
tributed some fungus-covered bugs from
the field of Mr. Mattocks in six infec-
tion jars. Into the jars had been put
soil taken from the yard, and green
wheat. Fresh chinch bugs sent by the
farmers were put into the jars - enough
to thickly cover the bottom. The jars
were covered with cheese cloth and set
into a glass case containing moist sand. The soil in the infection jars was not
watered, so that the bugs were in a
humid atmosphere but not in contact
with water.
We weiw in this way able
to secure the best conditions for the de- velopment of the fungus. When the
bugs died in the jars new bugs from the
field m7ere put in-- the date of restock- ing being also a record of tlie time
when the b~~gs in the jars had nearly all died. The following is the memoran-
dum for the six jars started May 23d :
May 23, June 4, June 20.
May 23, May 27) June 4, June 15.
May 23, June 4, June IS.
May 23) May 27, June 4, J~me 15,
June 20.
May 23 , May 27, June 4, June 15,
June 20.
Seven jars were started May 25th.
Their record is as follows :
May 25, June 4, June I 9.
May 25, June 4, June 15.
May 25, June 4, June IS.
May 25, June 4, June IS.




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228 p.!? ~~~~. [March 1S92-
May 25, June zl June I I, June 20.
May 25, June 4, June I 5.
May zsl June z, June I I, June 19.
Four jars started May 27 have the
following record :
May 27, June 6, June 15.
May z7? June I I, June IS, June 20.
May 27, June 6, June IS.
May 27, June 6, June 15, J~me 21.
Thirteen jars started June znd, each
jar being infected with four fungus-
covered hugs from the preceding jars,
are recorded as follows :
June zl June I I
June 20.
J~me 2, June I I, June 19.
June 2, June I I, June 19.
J~me z, June 7, June I 5.
June 2, June I I, June IS, June 20.
June 2, June &
June 19.
June 2, June I I, June 19.
June 2, June I I, June 20.
June 2, June 15.
June 2, June I I, June I 9.
June 2, J~me I I, June I 9.
June z, June I I, June IS, June 2 0.
June 2, June I I, J~me IS, June 20.
One jar started June 4 ran :
June 4, June i I, June 20.
One jar started June 5 ran :
T~me sl June 15, June 20.
Four jars started June 6 are recorded :
June 6? June I 5, June 20.
June 6, June IS? June 19.
J~me 6, June IS.
June 6, June 19.
The b~lgs put into the jars on the sev-
eral dates were from all parts of the
chinch bug district of the State of Kan- sas. They were for the most part just
received from the mail and were in vig-
orous condition.
They were kept sup-
plied with green wheat. While the bugs
in the infected jars were dying at inter- vals of five to ten days, bugs from the
same lots in isolated check jars remained alive and vigorous.
By June 20th the demand for inf'ected
bugs was so large that the jar method of infection required more attention than
we were able to give it. The results of
our separate lots were so uniform and
the Sporotrichum so vigorous and ever-
present that the further watching of sep- arate lots seemed useless. Accordingly
June 20th a large glass case was ar-
ranged wit11 damp sand three inches
deep over the bottom.
About ten dead
bugs covered with Sporotrichum were
scattered over the sand and large quan-
tities of live bugs from the field were
put in, with plenty of green wheat. In
nine days the bottom of the case was
thickly sprinkled with white fungus-
covered bugs and in thirteen days only
a few live bugs remained and the case
was restocked. The infection continued
to work so rapidly in this case that we
found no trouble in filling from it
twenty-five to one hundred orders daily. Vast numbers of young red chinch bugs.
were put into the case together with the adults and they too were an easy prey
to the disease. Minute points of white
made their bodies conspicuous among
the larger flecks of white where the
adult bugs lay covered with Sporotri-
chum.
On June 28th Bm$usa a$hidis was
first noticed in the infecting case.
Up
to this date it had not made its ap-




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March 1892.;
pearance in our laboratory in 1891.
From this time till the middle of August it multiplied its victims in the infecting cases. For a short time it became
more conspicuous than Sporotrichum
and then subsided.
On July 4th we began experimenting
with common shalbw dry goods boxes
for infecting cases. The inside of the
boxes was sprinkled and the bottoms
,thickly covered with green wheat. A
few fungus-covered bugs were 6prinkled
over the wheat and new bugs from the
field were p ~ ~ t in in large numbers.
Within a week the white fungus-cov-
ered bugs were thickly spread over the
bottoms and in places the white bugs
were literally in heaps. Continued ex-
periments showed that damp wooden
boxes ogered the best conditions for the development of the fungus and the glass
cases were no longer used. Sporo-
trichum, like most fungi, thrives best
in a moist atmosphere, but an excess
of water, such as occurs in a wet soil
or along the sides of a glass case where the vapor often becomes condensed, is
detrimental to its development. In the
wooden boxes the atmosphere was abun-
dantly humid ; but water that was
sprinkled in from time to time or that
became condensed on the sides of the
boxe6 was at once absorbed by the
wood.
During Julj- and August Sporotrichum
continued to spread through successive
lots of fresh bugs from the fields. Em-
pusa was always present but was not
so conspicuous in its ravages as Sporo-
trichum. In the first weeks of Sep-
tember the diseases began to subside
and by the middle of October neither
Sporotrichum nor Empusa appeared to
be spreading further.' Nor is it at all
probable that the diseases are lost. The observations on the life history of these fungi which follow show that provision
is made for a period of rest.
June 28th the spores of Sporotriclium
were transferred by means of a sterilized needle from the dead body of a chinch
bug to fifteen culture plates. The cul-
ture medium was a mixture of beef
broth and Irish moss ; enough of the
mucilaginous decoction of' the moss
being added to the beef broth to give
a solid medium at 80' F. Within forty-
eight hours the spores had germinated
and branching mycelia could be seen
spreading through the medium. With-
in three days spores were produced in
abundance, but only one spot on one of
the fifteen plates was found to be a pure culture, Aspergillus inucor and bacteria being mixed with all the other growths
of Sporotrichum. From the one pure
spot spores were transferred to three
new plat&, and the resulting growths
were all pure.
The germinating spore puts forth a
mycelium which branches as it grows.
At intervals mycelial branches shoot
upwards and grow over the surface of
the culture medium. Conidiophores
arise from these ; the conidiophore
sends off branches and the spores or
conidia are abscissed from these branches in clusters. The average diameter of
twenty spores thus produced was 2.3
micromillimeters. It is by means of




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PSYCHE.
[March 1892..
these minute spores that the fungus is
so rapidly disseminated throughout a
field infested with chinch bugs. These
spores, however, %oon lose their vitality (spores one month old would no longer
germinate in our laboratory) and the
fungus must make provision for its self- preservation during protracted periods
of weather unfavorable to the develop-
ment of conidial spores.
Culture plates in our laboratory, cov-
ered with pure cultures of Sporotrichum
planted July 9, show the inycelial
branches within the culture medium to
be swollen at intervals to a diameter of 3.9 to 8.8 micromillimeters; the aver-
age diameter of the unswollen mycelial
branches being about 2.5 micromilli-
meters. It seems more than probable
that the function of these hyphal bodies is to carry the fungus through the cold
of winter or the drought of summer.
Experiments have been started in our
laboratory to test the germinating power of these bodies, but too late to give the results in this paper.
Resting spores are also found on the
culture plates having a diam'eter of 20
micromilliineters, and a thickness of cell wall of I .8 i~~icromilliimeters. Similar spores are found in the crushed bodies of chinch hugs covered with Sporotrichum.
While it was found that pure cultures
of Sporotrichum could easily be ob-
tained, repeated attempts to inoculate
chinch bugs from these pure cultures
were unsuccessful.
As heretofore stated Empasa @hidis
was first noticed in our infection case
Tune 28. Eight or ten bugs were found
covered with a vigorous growth of this
fungus. This disease had probably
been sent in from some field where it
naturally existed. Empusa continued
to multiply in the infection cases and by July ~zth it rivalled Sporotrichiim in
the number of its victims. Active bugs
without external sibs of disease in the
afternoon would be found hanging to
the wheat blades the following morning
covered with a vigorous growth of Em-
pusa. If the fungus were left undis-
turbed it would keep on growing at
the expense of the tissues of the bug
until nothing were left save bits of the' chitinous integument.
Attempts were made to obtain pure
fruiting cultures of Empusa, but without success. At first bugs covered with
Empusa were placed on the surface of
the culture medium in the hope that the
spores would be thrown, as is the habit
with this fungus, and the growth of these spores would give a pure culture. The
spores were thrown in a ring about the
bug to a distance of a quarter of an
inch, but a rapid growth of bacteria
from the bug broke down the culture
medium and the Empusa spores did
not develop.