Technique and equipment for handling two hymenopterous parasites of the European corn borer, with particular reference t...


Material Information

Technique and equipment for handling two hymenopterous parasites of the European corn borer, with particular reference to prolonging their hibernation
Physical Description:
Arbuthnot, K. D
Baker, W. A ( William Alfonso )
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture, Bureau of Entomology and Plant Quarantine (Washington, D.C)
Publication Date:

Record Information

Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 30261881
oclc - 778371790
System ID:

Full Text

December 1938

United States Department of Agriculture
Bureau of Entomology and Plant Quarantine


By K. D. Arbuthnot and W. A. Baker, Division of Cereal
and Forage Insect Investigations,


The synchronization of liberations of a parasite with the occurrence
of its host in stages suitable for attack sometimes necessitates manipula-
tions of the parasite in order that it may be available for colonization at
the desired time. This problem has been encountered with Microgaster
tibialis Nees and Eulimneria alkae Ell. and Sacht., two hymenopterous
parasites of the European corn borer (Pyrausta nuhilalis (Hbn.)). when they
have been imported into the United States from Europe and the Orient (2, 4,
5, 6, 7). The equipment, constructed to handle the emergence of these
species, has been found readily adaptable to other parasites.


The manipulation of the parasites was accomplished in the following
two phases: (1) Storage from the time of their receipt at the laboratory
until the time for starting development to provide for synchronized field
releases, and (2) development of the material following storage, including
emergence of adults and their transfer to cages for transportation to the
field location. The facilities provided for these activities and the
equipment utilized are described in the following paragraphs.

The emergence cage (fig. 1) is 7 by 7 by 15 inches, with wooden top,
bottom, and ends, and with open sides to form the front and back of the cage.

1 These data were accumulated at the Monroe, Mich., field laboratory
for European corn borer research from 1928 to 1932, as a part of the program
for colonization of parasites of the European corn borer in the Lake States
area. The assistance of fellow workers in this project is acknowledged as
follows: G. T. Bottger, who conducted the work in 1928; Philip Luginbill
and E. W. Beck for the photographs; and Arlo M. Vance for helpful suggestions
in the preparation of the manuscript.



The edges are smooth and even to facilitate close fitting of the front and
back. Wooden strips (I by inch) are fastened flat along the front and
back edges of the bottom. The front and back are 7 by 15 inches. Each
consists of a frame,, constructed of 3 by A inch wooden strips, over the
inside of which 40-mesh copper screen is stretched and tacked to the outside
of the frame, presenting a smooth screen surface which fits tightly against
the edges of the cage. (An extremely close fitting of these surfaces is
necessary to prevent the escape of chalcid hyperparasites.) The front and
back are held in place by four No. 105 rubber bands, which are fastened to
the corners of the back, stretched across the cage, and each one fastened
to the proximal corner of the front.

The migration cage (fig. 2) consists of four wooden frames of 1 by 1
inch material, over the inside of which two thicknesses of a good grade of
cheesecloth are stretched and tacked to the outside of the frame. These
frames are fastened together by screws, to form the back, top, and ends of
the cage, the inside dimensions of which are 15 by 20 by 34 inches. This
cage rests on a plain wooden table having a top dimension of 24 by 40 inches
which serves as the bottom of the cage.

The migration light consists of a metal reflector constructed to
concentrate the light and having an 18-mesh wire screen front to prevent
the entrance of parasites into the reflector. A 40-watt frosted bulb sup-
plies the light. This unit is mounted on an adjustable tripod, 1 foot
behind the back of the migration cage.

The suction unit is adapted from a small hair drier, with all parts
except the motor, handle, and fan casing removed. A brass collar,. 2 inches
in diameter and 1 inch deep, is soldered to the fan casing, around the
suction opening of the fan. The collecting cage is a celluloid cone, with a
base 2 inches in diameter, with 80-mesh copper screen cemented to the inner
edge of its base, and an apical opening L inch in diameter. A ring of
celluloid, inch wide, is cemented to the base of the cone to increase the
friction surface coming in contact with the brass collar when the cone is
inserted into this ring. The parasite cone is 10 inches and the hyperpar-
asite cone 6 inches in length. This cage will accommodate 50 Eulimneria
alkae or 100 Microgaster tibialis.

The liberation cage is of the same construction as the migration
cage (wooden frames covered, inside, with cheesecloth, and screwed together),
except that one end has a removable composition wallboard cover, held in
place by rubber bands which are fastened to the wooden frame and stretched
over the cage end. A hole in this end, 1 inches in diameter, is stoppered
by a cork and provides the opening through which the collecting cage is
inserted when parasites are transferred from the migration cage into the
liberation cage. The cage is 8 by 10 by 16 inches inside dimensions and
will accommodate 2,500 Eulimneria alkae or 5,000 Microgaster tibialis.

A series of rooms were designed to facilitate efficiency in handling
the parasites during emergence and preparation for liberation in the field,


and, at the same time, to provide maximum precautions against the escape of
hyp!rparasites. The arrangement of the rooms and equipment in them is shown
in figure 3. A basement room 11 by 13 feet (143 square feet), with cement
and stone block walls, and a ceiling of composition wallboard, 6 feet high,
was divided by double wallboard partitions into three rooms of the desired

The emergence room, having 66 square feet of floor space (6 by 11
feet), is the most remote from the laboratory entrance. It has the natural
earth floor left after excavating, since the native clay was found to pack
firmly enough to form a satisfactory floor. Temperature and humidity are
controlled by equipment previously described by the authors (1). Racks which
hold the emergence cages are built along the walls of this room.

The workroom and trap room floors are of solid cement construction,
since they must withstand considerable wear and also must be dried and
cleaned when they have become wet or littered as a result of activities
incident to parasite handling.

The walls and ceiling of the workroom are painted white to facilitate
detection and collection of insects which escape from the migration cage.
An opening from the ceiling of this room to the out of doors, 16 inches
square and covered with 80-mesh copper screen, has an adjustable trapdoor
closure, which permits temperature control of the workroom by ventilation,
Without the ventilating arrangement, the escape of heat from the emergence
room into the workroom, through the communicating door, often raises the
temperature of the workroom above 750 F. A temperature of 701 to 750 allows
sufficient parasite activity for the migration of the insects but does not
allow excessive activity, such as occurs with higher temperatures and inter-
feres with the handling of the parasites. All manual operations incident to
emergence and preparation of the adult parasites for release in the field,
except the wrapping of shipping containers, are conducted in this room.

The trap room is for the purpose of preventing escape of insects,
especially hyperparasites, from the work and emergence rooms. Its principal
feature 4.s a lighting arrangement consisting of a 40-watt frosted bulb
inside a depressed wall section which is 2 feet square and 6 inches deep,
covered by a single-glazed glass, set flush with the wall. The light is
operated by a switch outside the door communicating with the laboratory
basement. This door is located in such relation to the light that it does
not receive any direct rays. When any equipment or person passes from the
workroom to the laboratory proper, a thorough brushing, to dislodge any
clinging insects, is administered in the trap room. Liberation cages, con-
taining parasites ready for field releases, are retained in this room until
they are removed from the laboratory for transportation to the field.

Emergence Technique

Since Microgaster tibialis and Eulimneria alkae are collected in the
cocoon ctage in Europe and the Orient during the winter months, shipped to


the United States, and reared in this country, the logical means of securing
adults later than the normal time of occurrence apparently is -to delay
emergence. The practical application of this method has been discussed in a
previously published article (2).

To evaluate properly the storage methods used for cocoons, it was
important to establish a suitable standard emergence method. Experience
with other parasites served as a guide for this work. Three environments
were used in this preliminary study, (1) outdoor cages, having wooden sides
and 80-mesh hardware cloth tops and bottoms, exposed to all prevailing
weather conditions, as representative of as natural conditions as possible,
with a definite precaution to prevent escape of hyperparasites; (2) cages
having wooden tops, bottoms, and sides, and 80-mesh hardware cloth fronts
and backs, in a cellar room, cooled by circulation of outdoor air when low
temperatures prevailed out of doors, and relative humidity maintained at
above 85 percent, a partially controlled condition, modifying natural con-
ditions; and (3) controlled incubator conditions, 800 F. and 80 to 85 per-
cent relative humidity. The results of test emergences in these environ-
ments are summarized in table 1I

Table 1.--Emergence of Microgaster tibialis and Eulimneria alkae under
three environmental conditions

Environment Microgaster tibialis Eulimneria alkae
1930 1931
Period Number Percent Period Number Percent
of emer- of emer- of emer- of emer-
gence cocoons gence Pence cocoons gence
Out of doors,
exposed to
natural May 1 May 15
conditions to 12 526 91.80 to 25 50 91.7
Cellar room,
cooled by
outdoor air,
relative hu-
midity above May 11 May 8
85 percent to 24 952 92.13 to 25 53 80.2
800 F., 80-85
relative Feb. 28 Feb. 15
humidity to Mar.15 152 88.06 to 26 50 91.5

The results shown in table 1 indicated no great difference in the
percentage of emergence secured by the various methods. Accordingly, the
la,' method (emergence under incubator conditions) was used as a basis for
comparison of all storage methods studied.


A temperature of 800 F. was used for emergence, since this was being
utilized generally in the laboratory for other purposes and was, therefore,
practical from the standpoint of equipment and space. General observations
on emergence in the years 1929 and 1930, however, showed a need for more
accurate information on the effect of humidity and contact moisture. In 1931
experiments were conducted to determine practical moisture conditions on
parasites in cocoons for securing the greatest numbers of healthy adult
parasites. Tables 2 and 3 contain the summarized results of these experi-
ments for Microgaster tibialis and Eulimneria alkae, respectively. In these
experiments all emerged adults were collected from the emergence cages daily,
and their condition noted.

Table 2.--Emergence of Microgaster tibialis at 800 F., with varying con-
ditions of relative humidity and contact moisture











Percent of
adults dead,








350 89.06 11.45
350 89.51 14.39

' Emerged from cocoons but died prior to removal at daily intervals.

Table 3.--Emergence of Eulimneria alkae at 80 F., with varying relative
humidity and contact moi-sture conditions


















Observations on vitality
of adults at time of
Many weak, not able to free
themselves of cocoon.
A few weak individuals.

Many weak individuals.
A few weak.

A few weak.
Good condition.

Good condition.
Good condition.


Examination of table 2 shows the desirability of a relative humidity
of 85 percent with contact moisture applied daily for securing the great-
est numbers of Microgaster tibialis for liberation purposes. Table 3 does
not show marked differences in rate of emergence occurring with Eulimneria
alkae such as appear with M. tibialis. However, the observations of the
condition of adults in the last column of this table serve as an index of
the desirability of the various conditions. The higher percentage of
emergence at 95 percent relative humidity with sprayed moisture applied was
undesirable because of mold, which quickly developed on the cocoons and
in some instances interfered with the emergence. Also, a few adults were
hampered by free water, which collected on the smooth surfaces of the
emergence cages and stuck them to the cage sides. When weak individuals
appear at the time of emergence, mortality at the time of release in the
field is greater than when all adults are strong at the time of emergence.
For practical purposes a relative humidity of 85 percent with daily sprayed
moisture proved the most satisfactory.

Storage of Cocoons

The emergence condition utilized for the determination of successful
cold-storage manipulation was a temperature of 800 F., relative humidity
85 percent, with daily application of sprayed contact moisture. In 1928
and 1929 commercial storage plants in Toledo, Ohio, were utilized. In
1930 and subsequent years a storage room at the Monroe, Mich., laboratory
equipped with a commercial storage unit was used,

Manipulation of Microgaster tibialis

With only one exception, which is mentioned later, all Microgaster
tibialis cocoons received in the early February shipments contained prepupae.
Each year the rates of emergence resulting after retention of prepupae in
cold storage from the time of receipt until removal from storage and place-
ment in emergence conditions during the latter part of June (to produce
adults for colonization from July 8 to 16, which is the desired time for
making liberations) have been satisfactory. The percentages of emergence
obtained each year and the numbers of cocoons utilized are shown in table 4.
The storage temperatures in 1928 and 1929 were maintained below 400 F., but
accurate records of the conditions were not obtained. In the other years the
temperature was maintained between 330 and 370 F. and the relative humidity
above 90 percent.

In 1932 one lot of cocoons, received in February, contained pupae
and adults as well as prepupae. Some of these cocoons were placed in the
incubator for emergence, without being subjected to cold storage, and the
remaining ones were placed in cold storage with the other cocoons. Sample
lots were removed from storage, some dissected and others placed in an
incubator for emergence, at intervals until the time when the cocoons con-
taining only prepupae were placed in the incubator (June 25) for emergence
for colonization purposes. The only change noticeable in the dissections
during this period was the death of the adults that were contained in the


cocoons, after approximately 2 months in storage. The emergence from cocoons
placed in the incubator on different dates was as follows: February 18,
67.86 percent; March 16, 39.04 percent; May 10, 19.07 percent; and June 25,
16.54 percent. An increasing number of deformed adults appeared in the
later groups. Further reference to these Microgaster tibialis adults is
made in the discussion of Eulimneria alkae.

Table 4.--Numbers of cocoons of Microgaster tibialis and percentages of
emergence in incubators after retention in cold storage from
February to June

Rate of
Number emergenc:
Year of cocoons (percent)

19281 300 74.0
19292 900 89.3
19302 12,500 86.2
19313 19,600 87.1
19323 14,000 88.4

1 An insectary room with no heat control; high humidity
maintained by evaporation from cotton bats.-
2 Controlled temperature of 800 F. and relative
humidity above 70 percent.
3 Controlled temperature of 800 F. and relative
humidity of 85 percent.

Manipulation of Eulimneria alkae

In 1929 the first attempt to delay the emergence of Eulimneria alkae
by cold storage was made, and the summarized data for each of the years
1929 to 1932, inclusive, are shown in table 5. The results obtained in
1929 were very unsatisfactory, the emergence from the 230 cocoons on July
1 being only 35 percent, as compared with approximately 70 percent from
300 cocoons in April. A greater number of cocoons were placed in storage
in 1930. Dissections of cocoons, made at the time they were placed in
storage, showed that they contained larvae and prepupae. Groups of cocoons
were removed from storage at intervals and placed in incubators (800 F.,
85 percent relative humidity). The percentages of emergence are shown in
table 5.


Table 5.--Numbers of cocoons of Eulimneria alkae and percentages of emer-
gence in incubators after retention in cold storage from February
to the time indicated

Time when
cocoons were Rate of
placed in Number emergence
incubators of cocoons (percent)
April 300 70.0
July 230 35.0
May 200 93.5
June 6,500 59.5
July 250 38.2
February 125 84.0
March 150 92.5
April 150 93.9
May 150 91.3
June 225 92.1
September 225 75.5
June 6,500 82.4

Dissections of the cocoons which failed to produce adults and the
condition of certain adults which emerged showed an increasing number of
individuals in the later groups having a type of deformity that had previous-
ly been observed (3, p. 15) in Exeristes roborator (F.), an imported parasite
of Pyrausta nubilalis, during laboratory rearings. This condition, in
E. roborator, was caused by cold-storage temperatures applied to the para-
sites while they were in stages other than a true hibernating condition
and was the same type of deformity seen later in Microgaster tibialis, as
heretofore mentioned. The observations made throughout 1930 indicated that
E. alkae responded favorably to the cold-storage treatment applied when the
stored cocoons contained only larvae which had not voided the meconium. The
voiding of the meconium apparently indicated a resumption of development
following hibernation.

All the Eulimneria cocoons received in February 1931 contained larvae,
none of which had voided the meconium. These cocoons were placed in cold
storage at a constant temperature of 350 F. and relative humidity of from 90
to 100 percent. They were removed from storage, and emergence was secured
under the standard emergence conditions. Dissections of cocoons throughout
the storage period showed that no larvae had voided the meconium, except in
the last group, which was dissected on September 9. In this group 8.3 per-
cent of the larvae had voided the meconium. Adults emerging from cocoons
which were. removed from storage during the last part of June were available


for colonization during the second week of July, which was the time desired
for making liberations in 1931. All the cocoons received in 1932, contain-
ing suitable larvae, were handled by this method, and an emergence of 82.4
percent was obtained for colonization.

Prolonged Retention of Adults

Very few of the cocoons of Microgaster tibialis received at the
laboratory have contained stages other than prepupae, and no effort has
been made to find a method by which this species could be handled when
received in other stages. However, each year a considerable portion of the
Eulimneria alkae cocoons received have contained stages other than larvae
which have not voided the meconium. Since these stages do not respond favor-
ably to the cold storage treatment previously discussed, tests of some pos-
sible means of retaining adults after emergence from their cocoons were
attempted in 1931.

Experience with various other species of parasites, in confinement,
had led to the generalization that an insect which does not hibernate in the
adult stage will have the greatest longevity in conditions that prevent
flight but permit enough activity to allow free feeding. Accordingly, the
nearest available approach to these conditions was used as a stal.ting point.
A basement storage room was selected for the experiments. For practical
purposes, arbitrary limits of mortality, from a minimum of 25 percent to a
maximum of 75 percent, were selected as a test of efficiency, the former
being considered "good" and the latter as too high.

Adults which had emerged after storage from cocoons at 800 F. and
85 percent relative humidity were used in this experiment. Sugar solution
and water on absorbent cotton were available to the insects at all times.
Table 6 contains the summarized results obtained,

Table 6.--Longevity of adults of Eulimneria alkae in confinement, under
various conditions of temperature, at relative humidities above
85 percent, and with sugar and water available for feeding,

Date fDate on jDays fromlMean tem-IDate on Days fromlMean tem-
of which the emergencelperature which the emergenceiperature from
emer- accumulated to 25% Ifrom laccumulatedtto 75% emergence
gence mortality jmortalityiemergencelmortality mortalitylto 75%
Iwas 25% Ito 25% jwas 75% Imortality
-___ _ImortalityV
Feb.22 Mar. 21 27 39.50 F. Apr. 12 49 41.5
Mar. 7 Apr. 1 25 40.00 F. Apr. 14 39 42.0
Mar.19 Apr. 10 22 42.50 F. Apr. 21 33 45.0
Mar.31 Apr. 23 24 47.0 F. Apr. 28 29 47.5
Apr.14 May 3 19 48.50 F. May 7 23 49.5
Apr.28 May 15 17 50.1 F. May 19 21 51.5
May 25 June 18 23 58.50 F. June 23 28 59.0

, Seventy-five males and seventy-five females were used in each date group.


Various other groups of adults were supplied with conditions ranging
from low temperature, which induced complete inactivity, to temperatures
in which flight was frequent. Water, sugar solution and water, granulated
sugar and water, and honey and water were used as foods. Under each of the
conditions utilized the rates of mortality were similar to those shown in
table 6.

Cocoons containing stages unsuitable for subjection to cold storage
are known to produce adults in numbers from approximately April 1 to May 15.
If these adults were retained under the above conditions, few, if any,
would be alive at the time desired for making liberation (July 8 to 13).
Dissections of individuals, during the time they were retained in the
above conditions, showed a rapid decrease in their fatty tissues after
7 to 10 days, with a corresponding lack of vigor as evidenced by decreased
activity. These data indicate that parasites received at the laboratory
in stages not suitable for retention in cold storage are of little, if any,
value for colonization,

Outline of Standard Procedure

By utilizing the information procured from the observations presented
in previous sections of this circular, a standard procedure has been es-
tablished for handling cocoons of hymenopterous parasites of the European
corn borer which have been imported for release in infested areas of the
United States, in order to insure their release in the field during the
optimum period. The procedure is briefly outlined in the following para-

Cocoons of Eulimneria alkae containing larvae which have not voided
the meconium and those of Micro2aster tibialis containing prepupae can be
successfully subjected to cold storage for the necessary prolongation of the
hibernation period. The condition of the parasites in their cocoons is
determined by dissection of a sample from each group of cocoons when they
arrive at the laboratory. If at that time the cocoons have a temperature
near that which is to be utilized for storage purposes, care is exercised
to maintain it during such handling as is necessary before they are placed
in storage. High temperature of cocoons upon receipt (450 F. or above)
is rectified by gradual reduction to the storage temperature, rapid changes
in temperature being avoided. A high relative humidity is maintained in
the packages of cocoons. This is usually insured by introducing moisture
on wet cloth wrappings.

Lots of cocoons collected from different localities, or at different
dates, are kept separately, since different groups of cocoons sometimes
show considerable differences in the numbers of contained hyperparasites,
in vitality, etc. Thus, if differences do appear, the data are not con-
fused by mixed groups.

When the individual lots are large (500 cocoons or more), a small
group (25 to 50 cocoons) from each lot is placed in the emergence environ-


ment, and er'snce :s s aciur e .
emergence for colonization purposes. This serves as an index of the num-
bers of adult parasites which will be available for colonization by showing
the contained percentage of hyperparasites, presence of other species which
cannot be detected except in the adult stage, sex ratio, and rate of emer-
gence. Cocoons suitable for storage are placed in containers which allow
them some air space. Nonrusting metal cans (3 by 5 inches) with screened
openings for ventilation have been used successfully for this purpose.
These cans containing the cocoons are placed in storage at a temperature
of 350 F. and relative humidity of 90 percent.

When cocoons are removed from storage for emergence, they are ex-
posed to a rise of 80 (from 350 to 430 F.) during the first 6 hours and a
rise of 350 (from 450 to 800 F.) during the next 12 hours. (This is the
temperature inside of the package, determined by inserting a ciAermometer
among the cocoons, with its upper end (scale) projecting from the package.)
1- gh humidity is maintained by wrapping the cans, containing cocoons, with
we- cheesecloth covered by an outer wrapping of three layers of heavy
wrapping paper, before the cocoons are removed from the storage chamber.

The usual means of accomplishing the temperature change just mentioned
has been to place the wrapped package of cocoons in a mechanical refriger-
ator, operating at a temperature of 42' F., and allowing the cocoons to
attain this temperature. Refrigeration is then shut off and the chamber
allowed to warm gradually, the temperature rising as indicated. If this
rise in temperature proceeds too rapidly, refrigeration is restored for
short periods to retard the rate of temperature increase. When the temper-
ature has risen to the highest point that can be attained in the refrigera-
tor (depending on surrounding conditions), usually 700 to 750 F., the pack-
ages are placed in the emergence room at 800 F. until the temperature of
the cocoons has risen to at least 750 F. When the cocoons have reached this
temperature, the packages are unwrapped and the cocoons are scattered in a
single layer on the bottom of the emergence cages. These cages are placed
in the ;ergence room, where a temperature of 800 F. and relative humidity
of 85 percent are maintained. Contact moisture is applied daily as a fine
stream from a special nozzle through the cage front. The amount applied is
that which leaves no free moisture on cage walls or bottom, but which gives
each cocoon a small amount of sprayed water.

During emergence all adults are removed from the cages once each day
by the following method: The emergence cages are removed singly to the work-
room and water is sprayed into the back of the migration cage and libera-
tion cage until the cheesecloth is well dampened and serves to hold granu-
lated sugar when it is sprinkled over these surfaces. A light is placed
1 foot behind the back of the migration cage and all other lights are
extinguished. Migration is accomplished by placing the emergence cage
just inside the open front of the migration cage, opening it, and allowing
the adults to proceed toward the light to the back of the migration cage.
Those adults which fail to respond to the light's influence are disturbed


with a camel's-hair brush to induce activity. When all the parasites have
left it, the emergence cage is closed and returned to the emergence room.

All hyperparasites are collected in the special collecting cage and
killed immediately in a cyanide jar. Primary parasites are collected in
the collecting cage by placing its open end close to each parasite, which
is then disturbed with a camel's-hair brush to dislodge it from the cheese-
cloth, the air current from the suction unit drawing it into the cage.
Fifty Eulimneria alkae or 100 Microgaster tibialis is the maximum capacity
of the collecting cage. The suction is then stopped and simultaneously a
hand is placed over the open end of the collecting cage to prevent escape of
parasites. The collecting cage is examined carefully for possible hyper-
parasites or other species of parasites which may have entered. The stopper
of the liberation cage is removed, the open end of the collecting cage
inserted, and its side tapped to dislodge the contained parasites, thus
causing them to fall into the liberation cage. The collecting cage is then
removed and the stopper replaced in the liberation cage.

All colonies remain in the liberation cage for at least 24 hours,
at temperatures from 700 to 800 F., to permit them to feed before being re-
leased in the field.

Literature Cited

(1) Baker, W. A., and Arbuthnot, K. D. 1931. An incubator room. Jour.
Econ. Ent. 24: 444-449, illus.

(2) ------and Arbuthnot, K. D. 1933. The application of artificially
prolonged hibernation of parasites to liberation technique.
Ann. Ent, Soc, Amer. 26: 297-302.

(3) ------and Jones, L. G. 1934. Studies of Exeristes roborator (Fab.),
a parasite of the European corn borer, in the Lake Erie area.
U. S. Dept. Agr. Tech. Bull. 460, 25 pp., illus.

(4) Jones, D. W. 1929. Imported parasites of the European corn borer in
America. U. S. Dept. Agr. Tech. Bull. 98, 27 pp., illus.

(5) Thompson, W. R., and Parker, H. L. 1928. The European corn borer and
its controlling factors in Europe. U. S. Dept. Agr. Tech. Bull.
59, 62 pp., illus.

(6) ------and Parker, H. L. 1930. The morphology and biology of Eulim-
neria crassifemur, an important parasite of the European corn
borer. Jour. Agr. Research 40: 321-345, illus,

(7) Vance, A. M. 1932. Microgaster tibialis Nees as a hymenopterous
parasite of Pvrausta nubilalis Hdbn. in Europe. Ann. Ent. Soc.
Amer. 25: 121-135, illus.

Figure l.--Emergence cage with front open to show
cocoons of Eulimneria alkae.

Figure 2-View of workroom showing equipment in use;
(a) ceiling ventilator with operating cord, (b)
migration cage, (c) miration light, (d) emergence
cage with front open, (e) cyanide jar for killin
hbperparaeites, (f) collecting cage attached to
oution unit, (g) work table, and (h) liberation


5-0X 66"

G'-e.X II-O



Figure ,3.-Plan of rooms and the contained equipment.



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