The temperature of the bee colony

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oOo TIN OF THE fe

USDEPARIMENT OFAGRICULTURE

No. 96 XS

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
July 22, 1914.

(PROFESSIONAL PAPER.)

THE TEMPERATURE OF THE BEE COLONY.’

3y Burton N. Gates, Ph. D.,
Formerly Apicultural Assistant, Bureau of Entomology.

INTRODUCTION.

There has been a decided need of accurate knowledge of the
temperatures and changes in weight of colonies of bees, particularly
_ring the winter. Previously existing data have not been gained
under controlled conditions, but generally by casual observations,
limited in number. Most of the previous work has also been for a
short period of the year. In this work an effort has been made
to get more reliable information by collecting data for practically
the cycle of a year. The knowledge of the changes in temperature
and weights is needed in a careful study of methods for successfully
wintering bees. This is one of the greatest difficulties which the
beekeeper has to meet, and it is hoped that the present work may
furnish data for a further study of the wintering problem. The
scope of the work here recorded is indicated by the following figures:

Period of experimentation, October 22, 1907, to September 26, 1908.

Number of observations, 2,576-++.
Number of separate readings, 20,000+-.

| APPARATUS.

The apparatus was constructed to meet emergencies which might
atise, which accounts for its many parts. It was planned so that the
complete apparatus could be upon the scales at all times, thus
obviating complications from corrections in weighings.

THE SCALES.

A finely adjusted platform scales was specially constructed,
which registered with a sensitivity of 10 grams to a maximum of
200 kilograms. It was expected that it would be possible to record

1 This report of work done for the Bureau of Entomology has been accepted by the faculty of Clark Uni-
versity, Worcester, Mass., as a dissertation in partial fulfillment of the requirements for the degree of doctor
of philosophy, and accepted upon the recommendation of Dr. C. F. Hodge. The author has been appointed
to the position of assistant professor of beekeeping, Massachusetts Agricultural College.

Nortr.—A study of the effects of temperature on bees, and of interest. to beekeepers generally.

38957°—Bull. 96—14—— 1

2 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE,

slight changes in consumption or*increase of stores. By means of a
double beam it was possible to counterbalance for extra thermometers
or other small special apparatus which might be added temporarily,
without necessitating a correction of the hourly readings. The
scales were found to be relatively satisfactory, but in times of heavy
wind extra precaution was necessary in order to overcome the
influence of drafts on the scales. In winter this could easily be
accomplished by closing the door
of the shed in which the experi-
ment wascarriedon. For outdoor
work, however, some difficulty was
experienced, as will be explained.
The agate-set bearings were also
sensitive to jar, which was con-
stantly guarded against.

THE THERMOMETERS.

Seven mercury thermometers
were used, of the type known. as
incubator thermometers, which
have a long stem and can be read
to fifths of a degree. One instru-
ment, however, used to register
the temperature of the outside air
was an ordinary chemical ther-
mometer. These instruments were
standardized and were graduated
to the centigrade scale.

THE HIVE AND ITS APPLIANCES.

Fic. 1.—The hive used in the experiment on the Figure 1 illustrates the general
temperature of the bee colony: A, storage cham-

ber for accessories, with door; B, bottom board APPearance of the hive, showing

with entrance; C , collar with feeder; D, brood the five stories. Only one of these
chamber; £, perforated zinc honey board; F, 4

second story for surplus; G,thinboardwithholes Was occupied by bees, as will be
for thermometers; HT, case protecting thermome- explained. The hive was of the
ters a-e; I, outside cover.
standard 10-frame Langstroth
type. Throughout the experiment it stood on the scales (fig.2). The
several parts were as follows:

A. The lower part consisted of a hive body with one side removed. To the
bottom was nailed a thin cover board, which served as the floor of the compart-
ment. The purpose of this chamber was to store fixtures, such as frames, “‘dum-
mies,’’ extra thermometers, and the like, while they were notin use. In this way it
was unnecessary to compute in the weighings for any change in the apparatus. For
example, in the winter, when four frames in the brood chamber were replaced by the
‘‘dummies,’’ these were taken from the storage chamber and the frames hung in their
place, without altering the weighings.

-The wedges also increased.

THE TEMPERATURE OF THE BEE COLONY. o

B. An ordinary bottom board.

C. This wooden collar contained the feeder and increased the space between the
bottoms of the brood frames and the bottom board. thus allowing the insertion of a
thermometer below the frames. The feeder was what is known as an Alexander
feeder. The end may be seen extending out of the collar at’the rear of the hive. In
this projection, which was provided with a wooden cover, the sugar sirup is poured
without disturbing the hive. The cover prevents drafts of air through the feeder.

D. Above the collar was the hive body in which the bees were located. The frames
were spaced with metal spacers (fig. 3), and wedges between the central frames held
all firmly in place. In this way everything was sufficiently secure to enable any
possible manipulation, even to turning the hive upside down, should it be necessary ,
without displacing parts.

the space between the
central frames sufficiently
to allow for the insertion.
of the stems of thermom-
eters. The gauge in
frames 3 and 4 permitted
the insertion of thermom-
eter e(fig.3). The frames
were wired and filled with
full sheets of foundation
before insertion. Two
holes were bored in the
middle of the front above
the entrance, for use in
case it should become de-
sirable to insert thermom-
eters. Throughout the
experiment these were
closed with corks.

'E. Between bodies D
and F' was a perforated
zine honey board.

F. A second body was
provided in case more
comb space should be-
come desirable.

G. The top of the hive
proper was covered with
a thin cover. This, as is
shown in figure 3, had
four holes drilled in the median line and one directly over the rear part of the space
between frames 3 and 4. Through these holes thermometers fitted in corks were
inserted.

H. This was a special hive body used as a protection for the thermometers. One
side, shown in figure 2, was removable so as to permit easy reading of the instruments.
In this chamber and around the thermometers were two cushions of ground cork, for
the protection of the tops of the thermometers and for the conservation of the heat of
the cluster in the extreme of winter.

I, A metal cover.

Fic. 2.—Hive on scales in shed where it was kept during the winter.

4 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

A series of clamps, which drew over screw heads, held the several
parts firmly together, preventing the bodies from sliding and snapping
the stems of the thermometers.

The ‘‘dummies’’. above mentioned consisted of ordinary frames
into which boards were fitted snugly. These were used in the winter
months instead of the two outside frames on either side of the hive,
thus forcing the cluster to occupy six frames in the center of the
brood chamber. In this way it was made certain that the cluster
would not shift away from the thermometers during the winter. The

Fic. 3.—The hive from above, showing the spacing of the frames. The corks in the cover indicate the
location of the thermometers.

“dummies” were removed when brood rearing became established

in the sprmg. These were not intended primarily for protection and
did not fit the hive tightly.

In order to eliminate the annoyance and possible complications
from propolizing, all the interior wooden parts were varnished and
polished to a piano finish.

It should be said that not all of the parts of the apparatus provided
were pressed inte service. The extra body, D, was not needed, and
consequently the honey board, F£, was not used. The outfit as

THE TEMPERATURE OF THE BEE COLONY. 5

actually used and as it appeared in position until the writer was
forced to move the experiment to the country in July, 1908, is shown
in figure 2

THE BEES.

Throughout the experiment Caucasian bees were used. Two colo-
nies were necessary. The first drew out the foundation in the frames
and was used during September and October, 1907. The second was
hived in November, 1907, and served throughout the remainder of
the experiment. This colony did not swarm.

THE ARRANGEMENT OF THE THERMOMETERS.

The thermometers were designated a, b, c, d, e, f,ando. Thermom-
eters a, 6, c, and d were inserted between the central combs. They
were arranged at regular intervals, a being at the front of the hive
and nearest to the entrance. Thermometer e was placed at the rear
of the hive between combs 3 and 4, and was expected to represent
the temperature of the margin of the cluster. Thermometer f was
inserted beneath the frames through the collar, as is described above.
Its purpose was to record the temperature of the air below the cluster
and which was likely to be affected by currents from the entrance.
Its bulb was directly below the central frames. The first five ther-
mometers extended about 7 inches below the cover. The outside
thermometer, 0, was suspended close to the hive in such a way as to
register the temperature of the air which surrounded the apparatus.

LOCATION OF APPARATUS.

The apparatus was installed in a shed on a third-story back piazza
in southwest Washington, as is shown in figure 2. While the shed
afforded shelter from storms, which was necessary for the protection
of the apparatus and in taking observations, windows and door were
left open, making the conditions relatively hike out of doors. The
shed was on the south side of the building.

In July, 1908, it was necessary to transport the experiment to
College Park, Md. This, however, was found not to have affected
the results. The apparatus was arranged in a situation comparable
to the shed in Washington.

CHECK COLONY.

Besides the colony on the scales, in which the thermometers were
suspended, a check colony in a hive with glass top and bottom was
set up close by. The hive was constructed with a glass bottom board,
and a wooden shield to cut out light. The cover was also of glass
sealed to the hive, on top of which were several thicknesses of felt
paper and an ordinary hive cover. By removing the bottom shield

6 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

and the top protection it was possible at any time of day or night
to look between the combs at the cluster. These protective cover-
ings were applied so as to be removed with the minimum jar. At
night, or even in the daytime, by means of a reflector, lantern light
could be thrown up between the frames. In this way the writer
was able to watch from day to day the shifting of the cluster and
the reaction of the bees to their environment and to compare this
with the readings of the thermometers in the hive on the scales. It
was necessary to maintain this check only during the winter period.

METHODS OF OBSERVATION AND RECORDING.

Since none of the instruments recorded automatically, it was nec-
essary to make frequent readings of both the weights and tempera-
tures. The experiment proper lasted from October 22, 1907, to
September 26, 1908. The first colony, used to prepare the combs,
was also under close observation, so that the whole period of experi-
mentation was almost a year. Readings were taken at least every
hour throughout the working day. Whenever the hive was manipu-
lated, or when peculiar meteorological conditions prevailed, readings
were taken half hourly, or even quarter hourly. On the average of
about once in three weeks, by means of assistance, it was possible to
take consecutive hourly readings for a period of two or three days.
In this way practically the whole activity of the colony for a period
of a year was recorded. During the summer months the readings
usually covered a period of 14 hours daily.

The temperatures were read to fifths of a degree. Weighings
were made to 10 grams. Every alteration or manipulation of the
colony was recorded. Hourly changes in the weather and activity
of the bees were also noted.

The readings were recorded on 12.5 by 20 cm. ecards, the size
standard to the office note file. Later from these tables the curves
of the temperature and weights were plotted on millimeter cross-
section paper, one sheet to a month. The method of plotting is
obvious from examination of the several curves herein presented.

THE CONSUMPTION OF STORES IN WINTER.

_ At the outset of the investigations it was hoped by means of deli-
cate scales, which have been described, that sufficiently accurate
weighings could be made to show whether there is any correlation
between the loss in weight and the temperatures of the cluster in
winter. For instance, it was desirable to know whether there is any
relation or rhythm in the consumption of stores to changes in tem-
perature due to metabolism. It has not been possible to detect any
such relations. Nevertheless several significant facts concerning the
consumption of winter stores have been discovered.

THE TEMPERATURE OF THE BEE COLONY. i

The rate of consumption of stores, as is shown in figure 4, exhibits
a relatively constant decrease from month to month. At the begin-
ning of the season, before the cluster was well established, when bees
were more active and before settled winter weather, food consump-
tion was greater than in midwinter. As the season progressed, during
February, for instance, consumption slackened. There are several
factors which may account for this. In the first place, as the winter
advanced there were fewer and fewer bees to be fed. The winter
was also less severe, and consequently less generation of heat was
necessary.

Humidity is another factor which noticeably influenced the daily
weights for a considerable part of February. This also occurred

co000

WEIGYT7” /N GCRAIVTS.

(oes
os

Sa:

Fic. 4.—Graphic representation of the loss in weight of the bee colony from November 6 to March 7,
due to the consumption of stores.

periodically in other months. Although condensation tended to
prevent a drop or even to raise the curves during a period of bad
weather, as will be shown below, the increased weight due to the con-
densed water vapor could neither be permanent nor affect the total
loss of weight during so long a period as a month. Whatever water
condensed during inclement weather would evaporate during the
following days of fair weather. Thus, while the scales might reg-
ister an increase during bad weather, consumption of stores was
actually going on all the time, but could not be detected in the
weights until fair weather had dispelled the moisture. Conse-
quently the records of single days are less significant than the aver-
ages of a month or of the season.

8 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

There was, however, a gradual and constant lessening of the daily
consumption of honey, as is apparent in Table I, which presents the
monthly and average daily figures. From this table it will be seen
that while in November the average daily consumption was 53.2
grams, in February the average was but 30 grams a day. For the
entire winter 43.5 grams of honey were consumed, on the average,

daily.

TaBLE !.— Monthly and average daily consumption of stores by wintering bees.

: W eight es Average dail
Time. | of stores. Monthly loss. las. y
| Grams. |Grams.| Pounds.| Grams. | Grains.
November (Nov. 6, 9 a. m., to Dec. 1,9 a. m.—25 days).. 6, 640 | |
5, 310
—— 1,330 2.932 | 53.2 | 821
December (Dec. 1, 9 a. m., to Dec. 31, 9 a. m.—30 days)_. 5,310
3, 820 |
EO | SSE 49.6 | 765
January (Dec. 31, 9a. m., to Feb. 1, 9 a. m.—32 days).--_. 3, 820 |
2,470
: 1,350 | 2.976 42.2 | 651
February (Feb. 1,9 a.m., to Feb. 29, 9 a. m.—28 days)... -| 2,470
1, 630
eer aL Seen 30.0 463
|
TOtGAIOSSHOr ANON TUS 26 ne ee or Se ee oe eee 5,010 | 11.045 |
IAW CT AS 7G al LY cl OSS ce es er oe eee Sk ee ee er Soe ee eee ee ee 43.5 671

TaBLeE I].—Daily loss in weight of colony of wintering bees.

l | | | |

|

: i ossane tee Loss in | : | Loss in | | Loss in |>
Date. crams. | Date. grams. | Date. | grams. || Date. | grams. |
||

Noy. 11 120 || Dee. 10 +30 || Jan. 10 7 Feb. 10 | 0
12 10 || 11 70 | 11 40 11 | 20 |

13 50 || 12 70 || 12 | +10 12 | 20

14 70 || 13 60 | 13 | 30 13 | 0

15. | 50 14 20 || 14 | 50 14 +40

16 | 80 15 25 15 | 60 15 +20
| 17 90 || 16 | 25 16 | 40 16 | 130 |
18 | 60 || 17 60 || 17 50 17 | 20 |

19 10 | 18 40 | 18 50 18 40

20 70 | 19 40 | 19 40 | 19| +440

——4

Although the foregoing figures represent the usual daily conditions,
they do not by any means represent the actual daily consumption.
As will be seen in Table IJ, there was no such degree of constancy as
is represented by these averages. Taking the 10 days at the middle
of each month, it is possible to represent prevailing conditions for
that month. Thus the data of Table II are a fair representation of
the actual variations as they occurred during the winter. It will be
seen in this table that the daily variation in weight is all the way from
a loss of 130 grams in some cases to no loss whatever or even an in-
crease of 40 grams. Therefore it is hardly possible to assume that the
weights of the entire hive will throw any light on the amount of
honey consumed in a single day.

This increase in the weight of the hive durmg bad weather is a
fact which, so far as the author is able to learn, has not heretofore

il Ne ttl i aint ae ei fe ke eee 2

THE TEMPERATURE OF THE BEE COLONY. 9

attracted attention. It can not be said in any wise that this 1s an
increase in the amount of stores. The phenomenon usually accom-
panied wet weather or fog and must be attributed to condensation
of moisture. In the check hive
moisture was frequently seen col-
lected on the glass top and even
on the frames and bees, but there
the conditions were perhaps less
normal than in the experimental
colony. Root! says that he has
seen confined moisture cause BEND

wane | Fea7 | Fane | eee

icicles to form in the hive. The ‘
condensation may become so §
great in extreme cases as to 4
- cause the bees to freeze together ‘
in asolid block when chilled down § |

by severe cold. (Root, pp. 332-
334.)

Honey is well known to be \ Y
hygroscopic, and if put into an eA : a
ice chest or a damp cellar, it xh uy

G

takes up moisture. Extracted 74°
Fic. 5.—Curve showing changes in weight of the bee

honey has also been observed to Collie Lei eae

accumulate enough moisture to

dilute it considerably. In the present case the hygroscopic property
of the honey can not be held wholly responsible for the increased
weight, although it may have contributed. Following an increase
of this kind, as has been mentioned, there was a marked decrease
with the coming of
fine weather and dry-
ness. For illustra-
tion, the increase of
40 grams on Febru-
ary 1 (fig. 5) occurred
during the early part
of the day, when it
was raining. That

afternoon and the

Fig. 6.—Curve showing changes in weight of the bee colony from Nov. following day there
20 to Nov. 23. 2

WEVG/TT- GRVIS

were fair weather and
wind. Then there came a marked decrease in weight, which not
only compensated for the increase during the storm, but also showed
that stores had been consumed constantly, although the weights

1A B Cand X Y Z of Bee Culture, 1908 ed.
38957°—Bull. 96—14——_2

10 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

failed to demonstrate it at the time. This same point is illustrated
by the figures presented in figure 6. Such conditions suggest the
complications which arise in attempting to correlate the colony tem-
perature with the consumption of honey.

GENERAL PHENOMENA OF THE CLUSTER IN WINTER.

During the winter the bees are relatively quiet; the cluster expands
and the bees fly only in the warmth of the warmest days. The heat
maintained in the cluster has a general relation to the prevailing
temperature of the air.

This relation of the cluster temperature to air temperature is
especially evident in a comparison of the maximum and minimum
temperatures of the several thermometers of the hive with the tem-
perature at the outside thermometer, 0. The daily maxima and
minima were practically synchronous for all of the thermometers
with the exception of c, which usually had its maximum when the
temperatures registered by the other thermometers were lowest.
Conversely, the minimum of ¢ occurred when the outside thermometer
and the others in the hive were at their highest points. This willbe |
explained in detail under a following caption. With the exception
of c, then, and for the particular conditions under which this colony
was kept, the minima occurred daily some time between 6 a. m. and
12 m., but usually about 8 or 9 o’clock. The maxima occurred daily
in the afternoon, usually between 2 and 4 o’clock. |

While ¢ registered the highest in cold periods, the temperature
recorded by the other thermometers showed a similarity with the
prevailing temperature of the air. Thus, in periods of cold, as for
example in December, the thermometers in the hive as a whole
registered lower than they did in warm periods. In warm periods,
when the bees are able to expand the cluster and move about, the
maximum cluster temperature lacked but a few degrees of the
maximum summer temperature. This is repeatedly shown in
figure 7; and in March, on a warm day, the temperature reached the
extreme of 33.2° C. (91.76° F.). The temperature of the cluster did
not fall below 17° C. (62.6° F.), and usually the bees did not permit
the temperature of the cluster to fall below 20° C. (68° F.).

- The amplitude of the fluctuations between the maximum and
minimum temperatures showed a close relationship to the external
conditions. In the center of the cluster, for instance, ¢ registered
much more constantly than the thermometers in the outside layer of
the cluster. The daily oscillations of ¢ were usually not greater than
1 to 5 or 6 degrees Centigrade. On the contrary, in the case of the
other thermometers in the hive which were more affected by the rise
and fall of the temperature out of doors, the amplitude of the oscilla-
tions was as great as 3 to 20 degrees Centigrade. The center of the
cluster, therefore, shows more clearly the activities of the bees. The

ee

THE TEMPERATURE OF THE BEE COLONY. 11

active portion of the cluster has a higher and more uniform tempera-
ture than the other parts, while the outside layers are subject more
directly, to the fluctuations of the winter weather. Most of the fol-
lowing study of the winter conditions of the beehive will be based on
the records of the center of the cluster.

It would naturally be expected that the heat radiating from the
bees would tend to delay the effects of the penetration of the cold of
the outside air on the cluster. In other words, it might readily be
expected that the cluster thermometers would reach their maxima and
minima later than the outside thermometer. However, this occurred
seldom and only in severe weather, when the changes were rapid and

considerable. Even then there was a delay of only an hour or two.

at the most. This
again suggests the
sensitlveness and
the responses of the
cluster to the
changes in the ex-
ternal air. The ad-
aptation of the bees
to changes in the

ESTAIELSS/VEO
DODD KEAP/NG

SW) \
. §

Q
, N
Nauti
Q \
2 N)

SFLBERUARY

tions will be more
apparent when de-
tails are considered.
As has been sug-
gested above, there
was a tendency for
the cluster gradu-
ally to maintain a
Fig. 7.—Schematic curve showing cluster temperatures of the bees dur- higher temperature
ing the winter and after brood rearing began. as the season ad-

vanced toward spring and the beginning of egg laying. Theschematic
curve, figure 7, presents graphically the conditions of temperature at
thermometer c throughout the winter. It will be noticed that dur-
ing the month of November, when the bees were less definitely and
constantly clustered, the amplitude of the daily variation and the
general temperature of the cluster were higher than in the succeeding
months. This is also evident in the fact that the curve of the ther-
mometer c at this time of the winter tended to follow the curve of
the outside thermometer o to some extent. In December, however,
there was a change in the course of the temperatures at c, in response
to the change in outside conditions. The conditions remained more
nearly constant from this time until egg laying commenced in the
spring, except that as the weather tended to warm up at the approach

DQDLECRLES ~- CLW7/IGRAIOE
hy
9

atmospheric condi-

+ Ghee Sars

12 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

of spring the mean of the cluster temperature also raised. Finally
when the days had considerably lengthened and were relatively
warm, the amplitude of the cluster variations increased, ass shown
in the schematic curve (fig. 7). When the summer season for the
bees began, accompanied by the beginning of incubation, the tem-
perature of the center of the cluster rose to 34° C. (93.2° F.) or 35°
C. (95° F.) and continued practically at this level. For the winter,
then, it might be said in a general way that the temperature prevail-
ing for several days is In a measure an index of the temperature of
the cluster.

TEMPERATURE BELOW FRAMES IN RELATION TO OUTSIDE AIR.

The thermometer f, situated below the bottom of the frames and
cluster, as is shown in the general views of the apparatus (figs. 1 and
2), registered the temperature of the air at the bottom of the frames.
It should have shown, if they were present, the effects of the cluster
on the temperature of the air below the frames. It might be expected
that the presence of the bees would have raised the temperature of
the air in this part of the hive. For comparison with the other tem-
peratures, thermometer o was hung in the shed in which the experi-
ments were conducted, and registered the temperature of the air
which enveloped the hive. Comparison of the readings of thermome-
ters f and o reveal some significant facts not altogether in accord with
the general belief of beekeepers.

During the winter as a whole these thermometers registered almost
identically. Slght variations occurred, but only for a few hours at a
time, and may be attributed to minor influences of the cluster, to
peculiar atmospheric conditions, to drafts, and to the agitation of
the bees. It should also be noted that the air which came in the
entrance entered from outside the shed and the temperature of this
air may not have been exactly that recorded by the thermometer o.

During the period of most protracted cold, from January 23 to Feb-
ruary 1, when the outside air ranged about 0° C. (32° F.), thermometer
f followed the outside temperature closely, and the course of the two
curves is practically the same. In some cases, as for instance on
January 26, thermometer f was slightly lower than the record of the
outside air, which may possibly be explained by lack of ventilation or
stagnation of the air of the hive. The lowest recorded outside tem-
perature was —10° C. (14° F.). Since it was impossible to read
these low temperatures on instrument f, and since the two curves are
parallel so far as records were possible, it may be assumed that ther-
mometer f would have registered almost the same as thermometer o.

During the warmest days and nights the recorded temperatures
were the same. The maximum for the winter period came on March

eg

THE TEMPERATURE OF THE BEE COLONY. iB

15, when the outside thermometer reached 22.6° C. (72.68° F.). In
all the other winter months there were days when the thermometers
registered only 2 or 4 degrees less.

In conclusion it may be said that throughout the season the tem-
perature below the frame was practically the same as that of the out-
side air. Of special significance is the fact that the daily extremes,
the maxima and minima, no matter what were the variations at other
periods of the day, were usually identical. From these observations

LLL AN

aaa perenne

DEGREES CENTIGRADE

See

ern
FRESE.

a
Z|
ie

Fig. 8.—Curves showing relation of temperature of center of bee cluster to outer temperature, Feb.
1 to 10.

it would appear that the contraction of the entrance and the tight
bottom board were not of much service in protecting the colony from
cold. Colonies without bottom boards have frequently been known
to survive extreme winter cold. It may be, however, an advantage
to a colony to be protected from the sweep of violent winds; but
there is no evidence that this colony appreciably warmed the lower
part of the hive in which it was wintering. Under such conditions
the bottom of the cluster is bathed in an atmosphere of the same
temperature as the outside.

' neared: cae ee

14 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

COMPARISONS OF TEMPERATURES OF THE CENTER OF THE CLUSTER
AND OF THE OUTSIDE AIR.

The curves have revealed no more striking results than the relation
observed between the temperature in the center of the cluster, ¢,
as compared with the temperature of the outside air, 0. These
curves (fig. 8) at times show a peculiar inverse relation; for instance,
when the thermometer out of doors registered low, below zero, the
thermometer in the center of the cluster registered high, and vice
versa, It should be observed that the maximum within the cluster
occurs practically simultaneously with the minimum outside, and
vice versa. Even minor changes outside are accompanied by cor-
responding inverse fluctuations in the cluster. The responses of the
cluster to the outside temperature were shown particularly by the
thermometer which recorded the temperature of the center of the
cluster, ¢c.

Up to the day of the first egg laying in the spring, March 9, the
general courses of c and o continued relatively constant. But with the
commencement of egg laying c changed its trend. The temperature
of the brood cluster then became more and more constant, as may be
seen in the results of the summer observations.

At first glance these curves might be interpreted as independent
of each other, that the outside atmosphere has no effect on the center
of the cluster, that it does not penetrate and modify the readings of ¢
as it appears to have done in the case of the temperatures in the margin
of the cluster. In all probability c more nearly represents the
activities of the bees than do the other temperatures; but there is a
relation of c to 0. It might be supposed that the reaction registered
by cis deferred for a period of hours and consequently appears at a
time when o has changed. For instance, corresponding to the
minimum of o on the 4th of February, the minimum of ¢ came nine
hours later. If this is due to a delay or “‘lag,”’ maxima and minima
in some cases are delayed for 24 hours or more. But this can not be;
there are many minor variations which appear on the curves, and
which are synchronous. Were there no relation of ¢ to o these minor
variations would either not have appeared in ¢, or, more especially, |
they would not have occurred simultaneously with a minor fluctua-
tion in the outside temperature. It is therefore impossible to explain
the phenomena on the ground of retardation (lag), for in that case it
would be far more constant than is evident.

Related to the assumed explanation by delay or “‘lag,”” humidity or
condensation, convection, radiation, and conduction might be
assumed to be factors involved. The experimental colony furnishes
no data for a consideration of humidity or condensation. The factors
of convection, radiation, and conduction can not be conceived as slow
enough to retard ¢ from 9 to 24 hours nor would it account forits minor,

THE TEMPERATURE OF THE BEE COLONY. 15

synchronous variation. Without doubt of these three factors the

loss of heat from the cluster by convection is sufficient to counteract
the hypothesis of the lag. Coupled with this the other factors would
be expected to participate. The convection is also modified by the
generally known contraction and relaxation of the cluster, referred
to elsewhere.

These physical phenomena are evidently unsatisfactory as an inter-
pretation from this standpoint of the lag. Thorough comparison of
the charts fails to provide suitable material for conclusions as to the
cause.

Table III shows the relative increase of temperature in the cluster
corresponding to the progress of the winter season, while Table IV
shows the monthly maximum and minimum temperature of the center
of the cluster during the period from November 9 to March 9.

Taste III.—Relative increase of temperature in the bee cluster corresponding to the
progress of the winter season.

Month. Range of temperature.
OL SH.
November, beginning of winter conditions..................------------ 20 to 24 68.0 to 75.2
IDGSCSHN DOP SSS SaHo CoSe COO HES SEA CSS Se Se Sets Ses ie aaa renee eee 20 to 22 68.0 to 71.6
ARE RI, TU THO) TUS SF os Sb Pe 8s eh ee a 22 to 25 71.6 to 77.0
YRIDS WOUWO PES SBS Sos See es eae a INSET ee ES aa re 23 to 28 73.4 to 82.4
LEG OUBIN CS CECA EB Oran SE Se eae ie eee as eee Pee ieests tinea 24 to 30 75.2 to 86.0
WIRE UNO s 6 Oh ESS SSS Oe SIGS OR SEIS SME Orel OS ne ae 27 to 32 80.6 to 89.6
Wihen brood rearingis established:---2. 222... 2. 2-2-5222. --- 2-2-2 ee - 34 to 35 93.2 to 95.0

Taste LV.— Monthly maximum and minimum temperature of the center of the bee cluster
during the winter period, Nov. 9 to Mar. 9.

Temperature of cluster.
Month.
Maximum. Minimum.
INGWGHDDOC So 6 ba bo acta axe See eee eae hee eo oe ets Ta Ope ees ee ana Ne eal 17° to 18.2° C.
SOL OO pe Mies ts eee kvei asd 62.60° to 64.76° F.

ID CRA TINO RAR he arse eee he Me scent ga ES Bi TG Sine 18.5° and 31.3° C.l..... 18.1° C.

65.30° and 88.34° F....| 64.58° F
TPIT cutee 6 So So cate ee tare cement eo ae aap SO S22 C2 tay Paes 19°C

S630 c8Re ero cen ae 66.20° F
IRGLORDRVAYE ssco ca aoe OCG O SICA ISS een Aree Terr ea area Boi WAS cy aaa weeny 21° C

SONGO SHY sreeere es Butea ea 69.80° F
Wie WEG) 6 SN A Ne ret i ey Ne ean ae Ba ae a Bo Den Ce ae een vie 27°C

OHI Se ipl ease IER) Sia 80.60° F

1 Ona very warm day, Dec. 28.

2 This occurred on two occasions, Jan. 14 and 30, at 8 a. m., when the outside temperature was 4° C. or
more below freezing.

3 Approximated several times when outside temperature was below freezing.

4 Occurred after a warm day; approaches summer conditions

EFFECTS OF MANIPULATION ON THE CLUSTER.

Good beekeepers know that it is not well to open a hive in winter,
but perhaps few realize the resulting effects on the colony. In
Washington there are days in every winter month which are suf-
ficiently warm to permit opening a hive without chilling the bees.
It was necessary, partially in order to observe the effects on the

16 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

colony and partially to know their condition, to open the hive under
experimentation. The results recorded by the thermometers on all
of these occasions are pronounced. In the course of the observations
on this colony it was found impossible to disturb the colony in the
shghtest degree, even to remove and replace a thermometer, to
jar the colony, or to puff smoke in at the entrance, without notice-
ably affecting the temperature. These effects, as in the case of open-
ing the hive, were not always temporary, but sometimes lasted for
hours. Any disturbance resulted in an almost immediate rise in the
temperature, and was appreciable throughout the cluster.

On March 12 the colony was opened for 15 minutes at 1 o’clock
in the afternoon. The thermometers throughout the hive and even
the one below the frames to some extent registered an immediate
rise in temperature. When the hive was closed the cluster was soon
reestablished but it was several hours before the temperature in the
margins of the cluster became normal. On the interior of the cluster,
however, the excitement and its effects were not so soon overcome.
The curve for ¢ shows that not until the next day did conditions ap-
proximate normal; the effects were evens even the day following
the opening of he hive.

These results agree with the experience of many practical bee-
keepers, who consider it unadvisable to open their hives during the
winter.

BEHAVIOR OF THE CLUSTER IN WINTER: OBSERVATIONS ON THE CHECK
COLONY.

By means of the check colony with glass top and bottom, described
on pages 5-6, it was possible to watch the movements of the bees
throughout the winter at any time of day or night.

Various theories have been advanced by beekeepers to account
for the behavior of bees in winter, but the writer is not aware that
they are based on continuous and close observation. For instance,
it has been maintained by some that bees semihibernate; by others
it is affirmed that there is at intervals a general warming up of the
colony in order thatit may feed. The theory is that at stated periods
bees generate enough heat to enable them to brave the cold and to
expand the cluster sufficiently to enable them to reach fresh stores.
It is not necessary to multiply theories on the condition and activities
of bees in winter.

In a previous portion of the text the relation of the temperatures
of the cluster to the temperature of the outside air has been suffi-
ciently considered. It remains now to describe the activity of the
bees as seen in the glass check hive. In some respects the move-
ments or the reaction of the bees, and more particularly of the cluster
as a whole, to the stimuli of changes in the atmospheric conditions
was rather pronounced.

THE TEMPERATURE OF THE BEE COLONY. IL 7

In watching this colony it was found that the density, and conse-
quently the shape of the cluster, varied from day today. When the air
outdoors was warm, the cluster expanded; with cold, it contracted.
The expansion usually did not cause the bees to cover more frames,
but caused them to cover more completely those frames which they
were occupying. Thus the expansion was usually downward toward
the bottoms of the frames and in the direction of the entrance.
With cold, the bees receded from the bottoms of the frames and from
the top bars.

At all times the colony was sensitive to the slightest jar. The bees
were also especially sensitive to the ight which burst in upon them
whenever the covering of the glass top was removed. If the hand
were passed over the glass, bees would fly toward it as if to sting.
This was noticed no matter how cold the day and shows that the
colony, and particularly the outside of the cluster, is far from torpid,
inactive, or semiquiescent. At practically all times there were bees
moving on the outside of the cluster or on the top bars of the frames.
Whenever the hive warmed up in the sun, although there were no
bees flying, this was evident. There can be no question, therefore,
of the alertness and activity of a colony in winter.

One of the most surprising observations was the apparent inter-
change of bees from the inside of the cluster with those on the outside
of the cluster. As the writer watched the cluster, the head of a bee
would gradually appear from below the bees forming the shell of the
cluster. Finally this bee emerged and took her place with the others
on the outside. Similarly, bees were frequently seen to disappear
into the mass. The behavior was in no way general, but apparently
was going on constantly and gradually. The phenomenon was
repeatedly observed under all manner of conditions and at different
times of day and night. By carefully arranging the covers, so that it
was unnecessary to remove them, and thus cause a jar, 1t was proven
that this behavior is normal and not the result of a disturbance of
the bees. It must be concluded, therefore, that in this way the same
bees may not be exposed to the outside cold for a long period. So
long as they are able to keep up their own body temperature they
remain outside, but when chilled they pass into the interior. Thus
there must be a continual interchange of bees from the outside to the
inside. Were it possible of observation, there would doubtless be
found a relation of the interchange to the meteorological conditions.
In cold weather the interchange may be expected to be greater.

In severe weather the bees were especially compact and their
arrangement definite and constant. They were arranged side by
side between the tops of the frames, with their heads downward. At
the lower part of the cluster they were also arranged head down but
with a little less regularity. It is difficult to see just what this means.

*

— i « 2 eae PP

18 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

As further evidence that the colony is not torpid in cold weather,
some of the other activities observed will be of interest. During the
day, particularly, the bees were seen grooming and combing one
another, feeding, and fanning at the outside of the cluster; and when
the light was admitted to the top, they sometimes flew up as if to
sting. It should also be stated that on nights of the most severe
weather the bees in both this check colony and in the experimental
colony were heard faintly and intermittently buzzing. This buzzing
was even more noticeable on cold nights than on warmer ones. A
peculiar trembling of the bee such as is seen in summer was not
infrequently noticed. All of these activities are commonly observed
in summer, but heretofore have not been thought to occur in winter
and spring before the colony is able to fly forth.

It is probable that the heat of the sun has no slight influence on
the cluster. At least in the check colony under observation it was
evident that the cluster sought the sunny side of the hive, the front
above the entrance, where from 10 or 11 o’clock in the morning until
sundown the sun shone on the hive.

TEMPERATURE ACCOMPANYING THE LAYING OF THE FIRST EGGS.

With the laying of the first eggs in the spring, which marks the
beginning of summer activity, striking changes occur in the behavior
and temperature of the cluster. The central thermometers 6 and c
were particularly affected. Upon opening the hive March 12 eggs
less than three days old were discovered. Up to March 9 ¢ had
usually continued its winter course inversely to 0, as is described and
illustrated above by figure 8. But after March 9, when the first
eggs were seen, the course of ¢ changed and the inverse relationship
was no longer apparent.

In order to explain the change in the course of ¢ in relation to 0,
the behavior of the bees at egg-laying time must be considered.
During the winter, while fresh air is necessary, there is no such need
of it as when the eggs, or more particularly the brood, appear.
Moreover, for incubation and for brood rearing a much higher and
more constant temperature is needed. The effects of drops in the
temperature of the outside air must be overcome. In preparing
room for the laying of the queen, the zone for the brood nest is
established, which is an important factor in the change in the course
of curve c. All of these things appear immediately in the curve
at the time of incubation. Formerly, when the bees went forth on a
warm day there was a drop in c; now the trend of ¢ is slightly upward
during the warmth of the day corresponding somewhat with the
warmth outside. Flight occurs nearly every day.

It is the belief of many beekeepers who winter their bees in cellars
that too high a temperature is likely to cause uneasiness and brood

THE TEMPERATURE OF THE BEE COLONY. 19

rearing. Root (1908) calls attention to the necessity of maintaining
a temperature of not more than 45° F. (7.22° C.) at the approach of
spring. The writer is not aware that any systematic study of the
temperatures of bees in cellars has ever been made, so that it is
impossible to say how the temperature of the cluster would compare
with that of the colony under experimentation. The prevailing
outside temperature, however, in the present experiment was found
to be about 45° F. (7.22° C.) for several days previous to the laying
of the first eggs, March 9.

At any rate in this experiment it appears that a temperature of
45° F. (7.22 C.), with an occasional maximum outer temperature of
8° to 11° C., is closely associated with the beginning of egg laying.
But there are probably other factors of importance, particularly the
matter of food. In establishing the experimental colony late in the
fall, it was impossible for the bees to store any pollen. In the spring,
however, for a week previous to egg laying they were seen gathering it.
This might be expected to be an important stimulus to egg laying,
and the bees could not rear brood until some could be gathered.
While there appears to be a close relation between stimuli, tempera-
ture out of doors, and pollen gathering to the laying of eggs, details of
the phenomena can be worked out only on a larger number of colonies
under experimental conditions.

Another noticeable phenomenon which occurred at this time was
the equalization of the temperature throughout the cluster. This
might occur earlier in colonies protected from the winds and in sunny
locations and later in colonies less favorably situated. If, however,
upon experimentation this should be found to be one of the funda-
mental stimuli to egg laying, it wouldin a measure explain the fact
that eges do not always appear at the same time in all of the colonies
of a bee yard. Another factor would be the strength of the colony
and the resulting heat which it could produce and conserve. These
results of the present investigation suggest great possibilities for dis-
covering the stimuli which regulate the beginning of egg laying in the
spring and which might influence the periodicity of brood rearing
during the summer.

So far the consideration has been largely of the period in which
eggs were laid and which preceded directly the beginning of incubation

or broodrearing. It will beseen, therefore, that this time is in a sense

transitional from the winter condition to the summer season, the
topic which will next be considered.

TRANSITION FROM WINTER TO SUMMER CONDITIONS.
The phenomena mentioned in the preceding caption which aceom-
panied the laying of the first eggs marked the beginning of the transi-
tion from winter to summer conditions, but this transition was not

20 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

eee

completed until brood rearing was well established. With the estab-
lishment of brood rearing, the changes which manifested themselves
with the first eggs became intensified. The course of the temperature
recorded at c became unlike that which was observed in the winter
and was influenced more directly by the outside temperature. The
influence of the outside temperature became less and less marked, as
is shown from the fact that the oscillation of ¢ became less and less,
the temperature in the center of the cluster became more constant,
and the temperature throughout the hive became more equalized.
As was stated, the turning point came on the 9th of March, but it was
a little more than two weeks, about the 24th or 25th of March, before
the colony really assumed normal summer temperature condition.
Once this was gained, the temperature, particularly of the center of
the cluster, remained relatively constant until fall. This transition
period of two weeks was characterized by several features.

There was an increase of temperature both in the colony and out of
doors. Out of doors the maximum ranged between 12° and 18° C.
(53.6° to 64.4° F.), but even more favorable weather followed the
establishment of brood rearing and the maximum ranged from 18° to
25°C. (64.4° to 73.4° F.). Toa certain extent the temperature of the
colony was raised like that of the outside temperature. The increase
was general throughout the colony and must be attributed to the
need of more heat for brood rearing, more ventilation, and the general
increased activity of the bees. At this time } and ¢ ranged constantly
between 33° and 35° C. (91.4° to 95° F.), which will be seen to be prac-
tically the range throughout the summer.

In a word, the transition from winter to summer conditions was
accomplished in a surprisingly short time. Accompanying incuba-
tion and brood rearing the temperature was gradually raised and
became equalized through the hive, and once well established was ~
maintained during the summer. Although the transition was rela-
tively abrupt, it would be expected to vary with the colony and —
perhaps be prolonged in unfavorable weather.

GENERAL PHENOMENA OF THE SUMMER TEMPERATURE.

The constancy and equalization of the temperature and the range
of 33° to 35° C. (91.4° to 95° F.), which characterized the close of the
transition from winter to summer conditions, characterize equally
well the prevailing summer phenomena. So constant were the tem-
peratures in summer that their peculiarities may be briefly sum-
marized. Few external factors influenced the hive temperature, and
these affected it but shghtly. In the original plan of the experiment
it was hoped that it would be possible to discover whether there is
any correlation between honey flows and temperatures; but inasmuch
as the season was excessively dry and the flowers secreted no nectar

)

THE TEMPERATURE OF THE BEE COLONY. Zit

for weeks at a time, this phase of the experiment could not be carried
out.
RELATION OF C TO THE OUTSIDE TEMPERATURE.

Whatever is said of ¢ in the following paragraphs applies equally to
b, and practically as well to all the thermometers in the hive.

Although the temperature at ¢ coursed constantly in the opposite
direction to o during the winter, there is no appreciable correlation
between the temperatures in the summer. It might be said of the
hive that the temperature as a whole was independent of external
conditions. A few exceptions to this will follow, however. During
a period of stormy and cooler weather, for instance, although there
were slight changes which will be discussed later, the temperatures.
were largely unaffected. Moreover, since the oscillation of ¢ was
slight, as will be explained, there was little relationship between the
temperature of the center of the cluster and o.

THE MAXIMA AND MINIMA OF C IN RELATION TO O.

The daily oscillation between the maximum and minimum of ¢
was usually less than 1° C. (1.8° F.), and in many instances it was but
one or two tenths of a degree. On the whole the temperature in the
brood nest is remarkably constant, ranging between 34° and 35° C:
(93:22) to 95-8.)

Even with this slight fluctuation there was perceptible on many
days a maximum and minimum for ¢, and particularly for the other
hive thermometers which perhaps were the most influenced by ex-
ternal conditions. It may be said that, roughly, the maxima and
minima occurred within two hours of the maxima and minima of 0,
but since in some instances this happened previous to the maximum
and minimum out of doors, the warming up of the colony due to the
increasing activity of the bees must have had its effect.

To show how closely the maxima of the thermometers in the outer
parts of the cluster ultimately approached the readings of the central
thermometers, it may be said that while in April the maximum of
the outer thermometers in the hive was 19° C. (66.2 F.), in the fol-
lowing months it rarely fell below 34° C. (93.2° F’.). In September,
however, with the general cooling of the atmosphere, it fell to 28° C.
(82.4° F.). This showed the tendency at the close of the experiment
for the colony to approach winter conditions. The facts show again
the unity or equalization of the temperature throughout the cluster,
which in the brood-rearing season ranges between 34° and 35° C.
(93.2° to 95° F.). The maxima and minima are shown in Table V.
The range of the oscillation shows the constancy of the temperature
during the height of the season and the greater fluctuations in spring
and fall.

a

I

ener = =a

22 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

TaBLeE V.—Maximum and minimum temperatures of the center of the cluster during
summer. Thermometer C.

e Sees Be | Approximate
Month. | Mz ximum. Minimum. | range.

a ee "a ee rice Pile
ADT 2 eee sarin <A ebro ono 20 35> aoe eae 35.4 95.7 31.6 88.9 = v2
Maye SOE a ee ee EE a a REA S. Se pee! 36.0 96.8 33.8 92.9 2 3.6
LY ETEYG ES Ss fea a es ee = eS a a SURE Be 35.5 95.9 33.6 92.5 2 3.6
Sulive? Aeron ee sete eee er see wae Vee Sheer eee 35.0 95.0 33.2 91.8 2 3.6
AST PRIS Go ieee oe Shes ae is Sago orale eee me 35.8 96. 4 33.8 92.9 2 3.6
DPORLenIgerss se fen. Bee SPARE Ee oe hep ee 34.8 94.6 28.0 82.4 7 12.6

FLUCTUATIONS IN THE HIVE TEMPERATURE AND THE CAUSES.

It has already been said that the fluctuations in the hive tempera-
ture were slight and that hot days and winds had very slight effect
on the cluster temperature. There are some minor fluctuations due to
internal and external disturbances which caused decrease or increase
in the hive temperature.

THE EFFECT OF “ORIENTATION” OR “PLAY FLIGHTS.”

Every beekeeper is familiar with the “play flights” of young bees
about noon on warm sunny days. These are generally believed to
be ‘‘orientation flights,’ in which the young bees fly forth in circles
and with head toward the hive in order to learn its location. During
the period of resumed brood rearing in August these flights occurred
every few days in the experimental colony. At such times ther-
mometer readings were taken at short intervals. Instead of causing
the heat of the hive to increase these flights first caused a decrease,
then aslightincrease. Table VI presents figures for a typical observa-
tion, made after the bees had been confined to the hive by inclement
weather for three days.

TasLeE VI.—EL£ fects of ‘‘ orientation flights” of bees on the temperature of the hive.

Thermometer.
Aug. 28. | |
a b Cc d é€ | rE 0
| | | |
Sel Che ik 8 colernicalerniealeriealer se I BOY GAM ESA Ce i TE
Came 34.0) 93.2 | 34.4) 93.92) 34.4 93.92) 34.4) 93.92) 33.6) 92 48) 34.6 94.28) 15.6 60.08
fpr 0 eee PSS 34.0) 93.2 | 34.4) 93.92) 34.4) 93.92) 34.0) 93.2 | 33.4) 92.12) 34.4) 93.92) 16.4) 61.52
8a.m.?._. 34.0) 93.2 34. 2) 93.56) 34.2) 93.56) 34.0) 93.2 33.4) 92.12) 34.6) 94.28] 16.8) 62.24
Qaim eee ae 34.0} 93.2 | 34.0} 93.2] 34.3) 93.74) 34.0) 93.2] 33.2) 91.76) 34.6) 94.28) 17.4) 63.32
AD ae ee 34.0} 93.2 | 34.2) 93.56} 34.3) 93.74] 34.0) 93.2 | 33.2) 91.76) 34.8] 94.64) 18.0) 64.40
5G Ue ie 0 Ee 33.8) 92.84) 33.8) 92.84) 33.8) 92.84) 33.8) 92.84) 33.2) 91.76) 34.2) 93.56] 19.4) 66.92
11.30 a. m.4_...} 33.8] 92.84) 34.0) 93.2] 34.0) 93.2 34.0) 93.2 33. 8 92.84} 34.4) 93.92) 20.0) 68.0
Le Bee nos 34.0} 93.2 | 34.0) 93.2 | 34.0) 93.2 | 34.0) 93.2] 33.6) 92.48) 34.4) 93.92) 19.6) 67.28
iP oe Tete 8 ee 34.0) 93.2 | 34.2) 93.56) 34.2) 93.56) 34.0) 93.2 33.6) 92.48) 34.8) 94.64) 20.2) 68.36
2 pamispee sa 33.8) 92.84) 34.0) 93.2 | 34.0) 93.2 | 33.8) 92.84 33.6) 92.48] 34.4] 93.92] 20.2] 68,36
ZAG Pwme te 34.0] 93.2 | 34.0} 93.2] 34.0} 93.2 | 34.0) 93.2 33. 6) 92.48) 34.4) 93.92} 20,4) 68.72
2.30 p. m.6. 34.0) 93.2 | 34.0) 93.2 | 34.2) 93.56) 34.0) 93.2 33. 6) 92.48) 34.6) 94.28) 20.0} 68.0 |
2:45 5p. ta ss 32h | 34.0] 93.2 | 34.2) 93.56) 34.2) 93.56) 34.0) 93.2] 33.8) 92.84) 34.8) 94.64) 20.4) 68.72 .
3p.m.........| 34.0] 93.2 | 34.2] 93.56] 34.2] 93.56] 34.0] 93.2] 33.8] 92.84) 34.8) 94.64] 20.8) 69.44
Apri est | 34.0) 93.2 | 34.4) 93.92 sees 93 “| 34.2 Po se 92.84) 34. 8) 94.64) 20.2) 68.36
1 Cloudy. 4 Quieted flight.
2 Bees fly slightly. 5 Bees fly freely again.

3 First good fly for three days. 6 Quiet again.

THE TEMPERATURE OF THE BEE COLONY. 23

It will be noticed that short flights were taken at 8 o’clock in the
morning when the thermometer ¢ fell 0.2° C. At 11 o’clock the first
flight of importance occurred. Then there was another shght drop
in the temperature followed by a rise. At 2 o’clock there was a
similar flight and change in the thermometer. In all cases within
15 to 30 minutes the thermometer had regained its normal tempera-
ture. While the drop was actually shght, when it is remembered
that the daily fluctuation in the temperature was frequently but a
fraction of a degree, the decrease was relatively considerable. The
same effect was noticed in the spring and in the early part of the
season, when the bees first commenced to take field trips. This
cooling effect must be attributed to the rushing forth of the bees
from the cluster; in so doing they liberate the confined heat of the
cluster. Another factor is probably the excessive fanning at the
entrance which usually accompanies these “play” flights. When the
activities wane and the bees commence to return to the hive, the
temperature resumes its normal condition.

A similar decrease in temperature was common in the early morn-
ing when the bees commenced to leave the hive for the field. For
comparison with the foregoing, the readings taken in the early morn-
ing of August 3 and 4 are presented in Table VII.

TaBLE VII.—E fects of early morning flight of bees on temperature of the hive.

Thermometer.
Date.
a | b Cc d € 0

Aug. 3. 2 OR ie STDS AE SOM GTN Ay ARON GE faba SCO fs Ne Re Cline (sae (fean| eens Ohare eee iW eel Chon [ies de
Sips ey eel 34.0 | 93.2 34.2 | 93.56 34.6 | 94.28 34.2 | 93.56 34.0 | 93.2 22.6 72.68
Oran esse oe 33.8 | 92.84 34.2 | 93.56 34.4 | 93.92 34.2 | 93.56 33.8 | 92. 84 26.0 78.80
LOA INES 33.9 | 93.02 34.4 | 93.92 34.8 | 94. 64 34.2 | 93.56 34.0 | 93.2 26.8 80. 24
Lae Ne aa i eee aes 34.0 | 93.2 34.4 | 93.92 34.8 | 94.64 34.6 | 94.28 34.0 | 93.2 27.4 81.32
WANE See ee sane 34.0 | 93.2 34.6 | 94.28 34.8 | 94. 64 34.6 | 94. 28 34.0 | 93.2 28.0 82.40

Aug. 4.
5a.m1__.......| 34.4 | 93.92} 34.6 | 94.28 34.8 | 94.64 34.6 | 94.28 34.2 | 93.56 21.2 70. 16
Gia eMmee eee 34.4 | 93.92 34.6 | 94. 28 34.6 | 94. 28 34.6 | 94.28 34.4 | 93.92 21.0 69. 80
7a.m2_.........| 34.0 | 93.2 34.4 | 93.92 34.6 | 94. 28 34.2 | 93.56 34.0 | 93.2 22.6 72.68
Sia LMS Ses 34.0 | 93.2 384.4 | 93.92 34.8 | 94. 64 34.4 | 93.92 34.0 | 93.2 25.0 47.00
Daas So 34.0 } 93.2 34.8 | 94.64 34.8 | 94.64 34.4 | 93.92 34.0 | 93.2 27.0 80. 60

1 Fanning entrance. 2 Bees begin to fly freely.

_EFFECTS OF CLUSTER HEAT ON THE TEMPERATURE BELOW THE
. FRAMES.

It was: found that the heat from the cluster had no perceptible
influence on the temperature of the air below the frames during the
winter. Practically the air was at the outside temperature. But in
summer totally different conditions prevail; the temperature within
the hive becomes equalized. Furthermore, the crowding of the bees
at certain seasons tends to force them to hang down from the bot-

2 ———_—_——-
SS

24 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

toms of the frames or even out at the entrance. Consequently that
space which was outside the frames assumes cluster conditions.

Early in the season f averaged 3° C. higher than o at all times;
at the end of the season, September, it averaged from 5° to 6° C.
higher. By the middle of May f stood only 1° or 2° C. lower than the
thermometers in the cluster, although the thermometer in the outside
air was much lower. Throughout the summer there was practically
no difference between ¢ and f. During the storm period, as will
be seen in Table LX, which is discussed farther on, f ranged even
higher than the prevailing cluster temperature. This was undoubt-
edly due to the massing of the bees below the frames as they were
crowded in from the alighting board.

THE EFFECTS OF STORM.

Since the summer of 1908 was remarkably dry and free from storms,
it is not possible to draw any definite conclusions upon the effects
of storms, cold waves, and winds upon the cluster temperature.
The only severe storm of the summer occurred in the latter part of
August. The outside thermometer went as low as 14° C. (57.2° F.),
while before and after this period there were frequent readings
ranging from 20° to 30° C. (68° to 86° F.). During the storm there
were several high winds. These, however, did not blow directly in at
the entrance. The bees were thus confined for three days, and at
times showed much evidence of shifting and massing at different
parts of the hive. In a glass observatory hive the bees were actually
seen to cluster now in one part of the hive and then in another.
The wind and rain also drove the bees in off of the alighting board
and forced them to hang from the bottoms of the frames. If the
readings of the thermometers nearest the outside of the hive are
rightly interpreted, the cluster withdrew from the walls of the hive,
and this caused a decrease in the temperature at these points. While
there is some evidence in the figures that the cold outside the hive
had its effects on the center of the cluster, the temperature was not
permitted to remain below 34° C. (93.2° F.). No fall was recorded
lower than 33.8° C. (92.84° F.). Thus the bees appear to be able
to control and conserve the temperature with remarkable constancy,
even though there be high wind and relatively low temperature.
Table IX, in comparison with the figures for a bright day in Table
VIII, reveal these facts.

THE TEMPERATURE OF THE BEE COLONY. 25
TasBLe VIII.— Temperatures of a bee colony on a normal day.
Time Thermometer.
Month | |
and day. Hour Ws | b. c | d. € 0.
Seeks | ; i 2! eh
|
ACen te Eanes Coenen ese Gey PCH i Ob 3 Be 8) 8 ON Aoki i SION eaE
NOT EN Os Oia yc. 34.4 | 93.92 | 34.4 | 93.92 | 35.0 | 95.00 | 34.8 | 94.64 | 34.8 | 94.64 | 24.4 | 75.92
7G) wines ape 34.4 | 93.92 | 34.4 | 93.92 | 34.8 | 94.64 | 34.8 | 94.64 | 34.6 | 94.28 | 26.0 | 78.80
G Ge dilseee age 34.2 | 93.56 | 34.4 | 93.92 | 34.8 | 94.64 | 34.8 | 94.64 | 34.8 | 94.64 | 24.6 |] 76.28
awa ee ys: 34.2 | 93.56 | 34.4 | 93.92 | 34.8 | 94.64 | 34.8 |] 94.64 | 34.8 | 94.64 | 25.8] 78.44
Ohare ess 34.6 | 94.28 | 34.6 | 94.28 | 34.8 | 94.64 | 34.6 | 94.28 | 34.6 | 94.28 | 27.6] 81.68
ID Bs ner ae 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 28.8 | 83.84
TIGA) adler ene 34.8 | 94.64 | 34.8 | 94.64 | 35.0] 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 29.0 | 84.20
ipeernsey- 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 29.6 | 85.28
72h Oya Oa a 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 35.2 | 95.36 | 35.2 | 95.36 | 30.4 | 86.72
4epsMeee ee oe | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 35.2 | 95.36 | 35.2 | 95.36 | 29.2 | 84.56
GipEaie ses. Se | 35.0 | 95.00 | 35.0 | 95.00 | 35.2 | 95.36 | 35.2 | 95.36 | 35.2 | 95.36 | 28.2 | 82.76
(De Aen ee | 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.2 | 95.36 | 35.0 | 95.00 | 27.6 | 81.68
Sa ee | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 26.6 | 79.88
Auge18|"@a. m...2-. 7) 34.0, 93.2 | 34.2 | 93.56 | 34.0 | 93.2 | 34.0] 93.2 | 34.2 | 93.56 | 21.8 | 71.24
(paces Bye ys | 34.2 | 93.56 | 34.2 | 93.56 | 34.4 | 93.92 | 34.4 | 93.92 | 34.2 | 93.56 | 22.0] 71.60
fo} Gh OMe a 34.2 | 93. 56 | 34.2 | 93.56 | 34.4 | 93.92 | 34.4 | 93.92 | 34.2 | 93.56 | 22.4 | 72.32
LS) eche 10 Oe ee 34.4 | 93.92 | 34.4 | 98.92 | 34.6 | 94.28 | 34.6 |] 94.28 | 34.4 | 93.92 | 25.0] 77.00
10 a.m.5....) 34.4 | 93.92 | 34.6 | 94.28 | 34.6 | 94.28 | 34.8 | 94.64 | 34.6 | 94.28 | 26.0] 78.80
saci wees 34.6 | 94.28 | 34.8 | 94.64 | 34.8 | 94.64 | 34.8 | 94.64 | 34.8 | 94.64 | 26.5 | 79.70
PIM eas a: 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0] 95.00 | 27.4 | 81.32
lGprsmises eee 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 28.6 | 83.48
PBJ Oe 1 tae 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0] 95.00 | 29.0 | 84.20
Spree se 34.8 | 94.64 | 34.8 | 94.64 | 35.0} 95.00 | 35.0} 95.00] 35.0} 95.00 | 28.0} 82. 40
4pm ees 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.2 | 95.36 | 35.2 | 95.36 | 28.0] 82.40
O) Owl seadaq 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.2 | 95.36 | 27.4 | 81.32
[JOS WOR aaa 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 26.2 | 79.60
Sipe derer ee 34.8 | 94.64 | 34.8 | 94.64 | 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 25.6 | 78.08
1 Cloudy and calm. 4 Clearing and calm.
2 Clearing, calm and close. 5 Clear.
3 Cloudy.
TaBLeE 1X.—The effects of storm and wind on the temperatures of the bee colony.
Thermometer.
Time. = :
a. b. e d. e€ is 0.
| | |
Month | Hour GM OHMIC! | PSRA OC. Ne Fe GOR) on) oR ee. om) lee |e
and day | |
DN. PAS) || te ee one 34.2 03, 56 |34. 4 |98. 92 |34. 2 /93. 56 |34.2 93.56 |34.0 |93. 20 [34.6 |94. 28 |20.4 | 68.72
8.30 a. m.../34. 2 |93. 56 |34.2 198.56 [34.2 |93. 56 |34.2 |93. 56 [34.0 93. 20 |34.6 |94. 28 |19.8 | 67. 64
Weks eles soe 34. 4 |93. 92 |34. 4 |93.92 |34.2 |93. 56 /34. 2 |93. 56 [33.8 |92. 84 |34.6 |94. 28 |19.8 | 67. 64
10a.m..... 34.0 |93. 20 (34. 2 |93. 56 |34. 2 |93. 56 |34. 2 ‘93. 56 |34.0 |93. 20 [34.6 |94. 28 |20.8 | 69. 44
11 a. m.3_.../34. 2 |93. 56 |34. 4 193. 92 |34. 4 |93. 92 134.2 [93.56 134. 0 |93. 20 {34.6 |94. 28 |20. 2 | 68.36
OAS Talal cies 34. 0 |93. 20 |384. 8 94. 64 /24.2 193. 56 [34.4 |93. 92 [34.0 |93. 20 [34.6 |94. 28 |20.6 | 69. 08
1p.m.4..../34.2 |93. 56 |34. 4 |93. 92 [34.2 193. 56 )34. 2 93.56 /34.0 |93. 20 [384.6 |94. 28 |18. 4 | 65.12
2H 1Os Week 34.0 |98. 20 |34. 6 194. 28 |34.0 |93. 20 |34.0 |93. 20 [34.4 |93. 92 [34.6 |94. 28 {17.8 | 64.04
Eo) ) Oe 6 erase 34. 0 |93. 20 |34. 4 |98. 92 |34.2 |93. 56 |34. 2 |93. 56 [34.0 |93. 20 [34.6 |94. 28 |17.6 | 63. 68
Aye Wee ee 34.0 |93. 20 /34. 8 |94. 64 |34. 2 /93. 56 [34.0 /93. 20 /34. 0 93. 20 [34.6 |94. 28 17.0 | 62.60
5 p.m......|34.0 |93. 20 |34.0 |93. 20 |34. 2 |93. 56 34.0 /93. 20 [34.0 |93. 20 [34.6 |94. 28 |16.2 | 61.16
| 6 p. m.4..../34.0 |93. 20 (34.2 |93. 56 |34. 0 |93. 20 |34.0 |93. 20 /33. 6 |92. 48 )34.6 |94. 28 18.2 | 64. 76
7 p.m....../34.0 |93. 20 |34: 4 |93. 92 34. 2 |93. 56 [34.2 |93. 56 [33.6 |92. 48 [34.6 |94. 28 }16. 4 | 61.52
8p. m....../33. 8 |92. 84 |34. 2 |93. 56 134.2 193. 56 134.0 (93. 20 |33. 4 |92.12 |34.6 |94. 28 |16. 2 | 61.16
9p. m_...../34.0 '93. 20 [34.2 193. 56 134. 2 193. 56 |34. 0 '93. 20 |33. 6 192. 48 |34. 6 194. 28 |15.0 | 59.00
OVO RMe eee 34. 0 193. 20 134. 4 193. 92 |34. 4 193. 92 |34. 4 193. 92 |33.0 |91. 40 |34. 6 |94. 28 |15.0 | 59.00
INL Osate oss 34. 0 193. 20 134. 2 193. 56 134. 4 193. 92 134.2 |93. 56 [33.2 /91. 76 /34. 6 |94. 28 |14.6 | 58. 28
7) joys lS ae 33. 8 |92. 84 /34.0 |93. 20 |34. 2 93. 56 134.0 |93. 20 |33. 4 |92.12 134.6 |94. 28 |15. 4 | 59.72
JN OSs AG |) Wee aoels eae oe 33. 8 |92. 84 |34. 2 |93. 56 [34.0 193. 20 |34.0 /93. 20 [33.4 [92.12 |34. 6 194. 28 |15.6 | 60.08
27a ae 33. 6 192. 48 |34. 0 193. 20 |34. 0 |93. 20 34. 2 |93. 56 [33.0 |91. 40 |34. 6 |94. 28 |14.8 | 58. 64
Spa Teoma eee 133. 6 192. 48 |34. 2 |93. 56 134. 2 |93. 56 [34.0 |93. 20 |33. 4 |92.12 /34. 6 |94. 28 17. 4 | 63.32
4a.m.6___.. 33. 6 192. 48 |34. 2 |93. 56 (34. 2 193. 56 (34. 0 193. 20 |33. 4 192.12 |34. 6 |94. 28 [16.2 | 61.16
5a.m.6___.. 33. 6 192. 48 {34.0 193. 20 34. 2 193. 56 [34.0 193. 20 |33. 2 |91. 76 [34.6 |94. 28 {17.0 | 62. 60
Gee 0G, oo 133. 6 192. 48 134.2 193.56 |34. 2 |93. 56 [34.0 193. 20 [33.2 |91. 76 [34.6 |94. 28 |16.6 | 61.88
TE Gig 100 ee 33.6 |92.48 34.4 |93.92 |34.2 |93. 56 |33. 6 92.48 |33.4 |92.12 |34.6 ee 28 {17.0 | 62.60
|
1 Cloudy. 4 Rain.
2 Breeze from north. 5 High wind from east.
3 Raining a little. 6 High wind from east, no rain.

26 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

Another fact to which reference has been made under the caption,
“Effects of cluster heat on the temperature below the frames,”’
should be mentioned here. During this period of storm, f frequently
recorded a higher temperature than the thermometers above it.
This was undoubtedly due to the crowding of the bees in off of the
alighting board, forming a curtain below the frames. This is an
advantage in helping to conserve the heat and in preventing the cold,
inward draft through the entrance from striking directly on the
brood.

THE EFFECTS OF TRANSPORTATION ON THE TEMPERATURE OF THE

COLONY.

Not infrequently beekeepers sustain heavy losses in moving their
bees, although it 1s not usually done in extremely hot weather.
Since the moving of the experimental colony to College Park, Md., a
distance of about 11 miles, was unavoidable, the writer decided to
make the most of the necessity and determine in so far as possible the
effects of transportation on the colony. Even with precautions,
strong and populous colonies sometimes smother. Brood is often
killed, supposedly from excessive heat. With these points in mind
every precaution was taken to protect the colony from harm; and
since no damage resulted, the experiment reveals the temperature
conditions in a successful transportation of a strong colony under
most adverse circumstances—extreme heat and humidity and bad
roads.

The trip was commenced at 10.30 a.m. on July 2. The day was
humid, with intermittent sunshine and clouds, and no breeze. In
Washington the mercury rose to 32.33° C. (90° F.) at 2 o’clock. The
road was through the city of Washington over asphalt and stone
pavements for several miles and then over rough country roads, which
had scarcely any shade. The colony was moved on a spring express
wagon with cover, the curtains of which were kept down on the sunny
side so as to prevent the sun from striking directly on the hive. The
other curtains were rolled up in order to allow all the ventilation
possible, but since there was no breeze all the draft which the
bees got must have been procured by fanning and by the movement
of the wagon.

The colony was crowded into a 10-frame Langstroth hive and the
entrance was screened the night previous. All of the thermometers
remained in position. This, of course, prevented giving ventilation
through the top of the hive, which is the common practice in moving
bees. In order to give room for expansion of the cluster and to con-
fine the air as little as possible, the hive was set over an empty body,
on the bottom of which wire cloth was tacked. In order to allow the
air to circulate freely beneath the hive, it was supported above the

THE TEMPERATURE OF THE BEE COLONY. wal

bottom of the wagon on §-inch strips of wood, the spring of which
relieved to some extent the jolt of the wagon. In the morning, before
the colony was disturbed and just after it was loaded, thermometer
readings were taken. On the road readings were also made at short
intervals. In this way the result of every successive event in the trip
was known.

The first disturbance, carrying the hive downstairs and loading, was
immediately responded to by the bees. The first 15 minutes on the
road were but slightly more disturbing. Gradually, however, the
temperature increased until 1.30 o’clock in the afternoon and an hour
previous to releasmg, when practically the maximum was reached,
36.0° C. (96.8° F.). It should be mentioned, however, that during
the next few hours and even after the bees had their liberty the ther-
mometers in the distant parts of the hive, a and e, registered 36.2° C.
(97.16° F.). But it is probable that the bees clustered more densely
at these points than they did in the center of the hive. This tempera-
ture can not be considered particularly abnormal, although it is
higher than any temperature registered immediately before or after
the transportation. On several occasions during the summer and
even in May, practically the same degree was reached; but since in
normal circumstances it never went higher than 36° C. (96.8° F.),
the temperature observed is probably nearly as high as can be reached
by bees without damage. It would not have taken many degrees
more than this to have softened the combs and to have caused them
to sag and break. The melting point of pure wax is 62° to 64° C.
(143° to 145° F.), but the difference between the melting point and
the point at which combs become soft enough to sag must be con-
siderable, perhaps 20° C. (36° F.).

It can not be said that the temperature was higher at any one part
of the hive than at another, unless possibly there was a slight tend-
ency for the brood cluster to be maintained cooler. This would
naturally be expected, but under such trying circumstances the phe-
nomenon could not be measured satisfactorily. At no time on the
trip did the bees hang down from their combs into the lower body,
and upon releasing them there was no evidence of condensation. At
all times, as would have been expected, there was considerable
fanning. Furthermore, the bees were not made cross by their con-
finement, as was the case when the rest of the colonies of the apiary
were moved, which was done under much more favorable circum-
stances except for ventilation. That no brood died in the experi-
mental colony is further evidence that 36° C. (96.8° F.) is not
abnormal. |

The colony was placed in its new position at 2.30 o’clock and the
bees liberated. The effects of their liberty on the temperatures were
not apparent, however, as will be seen in Table XI, for more than an

28 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

hour, when the temperatures began gradually to fall. Finally, when
the bees had orientated themselves and had commenced to return to
the hive, there was a noticeable quieting and a perceptible drop in
the mercury. At 7.30 o’clock, after all the bees had returned to the
hive, conditions were pee eallee normal.

in conclusion it may be said that the conditions under wail the
bees were moved, although trying and about as adverse as possibly
could be encountered, did not produce abnormal heat in the hive.
The temperature increased only 2°, from 34° to 36°+C. (93.2
to 96.8° F.). While it is generally admitted that ventilation from the
top is preferable in moving bees, on the hypothesis that warm air
rises, ventilation from the bottom was a success in the case under dis-
cussion. In moving the rest of the department apiary to College
Park earlier in the season, when the weather was more favorable, the
day being cloudy with showers, three colonies suffered severely from
overheating and condensation. These colonies were screened at the
entrance and over the top of the hive; but apparently the screening of
the top was not sufficient, because when the bees became excited and
expanded as a result of the heat, they packed so tightly against the
top screen as to shut out all ventilation. The tendency of bees is
upward and toward the light. On the contrary, if ventilation is given
from below, there is less tendency for them to pack against the screen.
While it is generally maintained that for moving colonies top ventila-
tion is preferable, the present experiment would indicate that bottom
ventilation is practical and advantageous.

For comparison, figures taken the day previous (Table X) and the
day after the transportation (Table XII), as well as on that day
(Table XI), are presented.

TaBLE X.—Readings of thermometers, July 1, on day previous to transportation of bee
colony.

Thermometer.

Hour. a. b. cG a é. 0.

“6, SH HOR ee AG; ee OS neal t ssi Ce FC AG SB
| |
CASI seer 33.4 | 92.12} 34.0 | 93.20] 34.0] 93.20 | 33.8 | 92.84 33.8 | 92. 84 25.8 78. 44
Oe ir ss ee eee 33.6 | 92.48 | 34.0 | 93.20 34.2 | 93.56 | 33.6 | 92.48 | 33.6 | 92.48] 27.0} 80.60
ha mbe ae. 33.8 | 92.84} 34.2 | 93.56 | 34.2 | 93.56 | 33.8 | 92.84 33.6 | 92.48 | 28.5] 83.30
PAS fete er tee 33.9 | 93.02 | 34.5 | 94.10] 34.5] 94.10] 33.9 | 93.02] 33.9 | 93.02 | 29.0] 84.20
1 oy 11 een 34.0 | 93.20] 34.5 | 94.10] 34.5] 94.10] 34.0] 93.20] 34.0] 93.20] 29.8] 85.64
PG cit eee eee 34.4 | 93.92 | 34.8 | 94.64] 34.8 | 94.64] 34.0] 93.20] 34.0] 93.20] 31.5] 88.70
SD MI ees So 34.4 | 93.92 34.8 | 94. 64 34.8 | 94. 64 34.0 | 93.20 34.0 | 93.20} 31.5 88. 70
4D. mete eess3 34.6 | 94.28 34.8 | 94.64 34.8 | 94.64 34.2 | 93.56 34. 2 | 93. 56 SPAY? 89.96
Pode Opal 02 Pape ge 34.8 | 94.64 34.8 | 94.64 35.0 | 95.00 34.8 | 94.64 35.0 | 95.00 29.0] 84.20
| | |

eee’

THE TEMPERATURE OF THE BEE COLONY. 29

Table XI.—Readings of thermometers during transportation of bees, July 2. Day
extremely warm and sultry.

Thermometer.
Hour. a | b | c d | e | Observations.
| | | | | |
TG °F SCR COE | 16K | OR (GL Out | 16! OE
ca a Mea ee af

Paems— 34.4 | 93.92 | 34.4 | 93.92 | 34.4 | 93.92 | 34.0 | 93.20 | 34.0] 93.20 | Hive closed but un-
moved.

10.15 a. m.} 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 34.8 | 94.64 | 34.8 | 94.64 Hive loaded on wagon.

10.30 a. m.| 35.0 | 95.00 | 35.0 | 95.00 | 35.0 | 95.00 | 34.8 | 94.64 | 34.8 | 94.64 | Drive to College Park
started.

10.45 a. m.| 35.2 | 95.36 | 35.0 | 95.00 | 35.1.] 95.18 | 34.9 | 94.82 | 35.0 | 95.00

Peapinees sont Gos ce |1o0. 2 | 95.36} 35. 2 | 95.36 | 35:0 | 95.00 |°35:.0 | 95.00

11.15 a.m_-| 35.4 | 95.72 | 35.0 | 95.00 | 35.1 | 95.18 | 35.0 | 95.00 | 35.0 | 95.00 | Sun and clouds.

11.30 a. m-.| 35.6 | 96.08 | 35.2 | 95.36 | 35.2 | 95.36 | 35.0 | 95.00 | 35.0 | 95.00 Do.

11.45 a. m-| 35.8 | 96.44 | 35.4 | 95. 72 | 35.6 | 96.08 | 35.1 | 95.18 | 35.2 | 95.36 Do.

Terenas 35.8 | 96.44 | 35.6 | 96.08 | 35.6 | 96.08 | 35.3 { 95.54 | 35.4 | 95.72 Do.

12.15 p.m-| 35.8 | 96.44 | 35.8 | 96.44 | 35.6 | 96.08 | 35.4 | 95.72 | 35.6 | 96.08 | Do.

12.45 p.m_-| 35.8 | 96.44 | 35.6 | 96.08 ! 35.6 | 96.08 } 35.4 | 95.72 | 35.6 | 96.08 | Stopped 30 minutes for

= lunch.

Ifo srae Sexe 35.8 | 96.44 | 35.6 | 96.08 | 35.6 | 96.08 | 35.6 | 96.08 | 35.6 | 96.08

1.15 p.m-..| 36.0 | 96.80 | 35.8 | 96.44 | 35.8 | 96.44 | 35.8 | 96.44 | 35.8 | 96.44

1.30 p.m--| 36.0 | 96.80 | 36.0 | 96.80 | 35.9 | 96.62 | 35.8 | 96.44 | 36.0 | 96.80

2p.m. 36.0 | 96.80 | 36.0 | 96.80 | 36.0 | 96.80 | 35.9 | 96.62 | 36.0 | 96.80 |

2.30 p. m..| 36.2 | 97.16 | 36.0 | 96.80 } 36.0 | 96.80 | 36.0 | 96.80 | 36.1 96.98 | Hive set on stand and
opened.

30s ines ace 36.2 | 97.16 |°36.0 | 96.80 | 36.0 | 96.80 | 36.0 | 96.80 | 36.2 | 97.16

3.30 p. m-_.| 36.2 | 97.16 | 35.8 | 96.44 | 35.8 | 96.44 | 36.0 | 96.80 | 36.0 | 96.80

Asp=im=sao2 36.1 | 96.98 | 35.4 | 95.72 | 35.8 | 96.44 | 36.0 | 96.80 | 36.0 | 96.80

4.30 p.m-_-| 35.4 | 95.72 | 34.1 | 93.38 | 34.8 | 94.64 | 35.1 | 95.18 | 35.4.| 95.72

pSMeses. 35.0 | 95.00 | 34.0 | 93.20 | 34.6 | 94.28 | 34.9 | 94.82 | 35.0 | 95.00

6.30 p. m-..| 34.6 | 94.28 | 34.2 | 93.56 | 34.2 | 93.56 | 34.4 | 93.92 | 34.4 | 93.92 | Bees all returned to
hive.

apenas 34.4 | 93.92 | 34.2 | 93.56 | 34.2 | 93.56 | 34.2 | 93.56 | 34.2 | 93.56 :

7.30 p. m..| 34.4 | 93.92 | 34.0 | 93.20 | 34.0 | 93.20 | 34.2 | 93.56 | 34.2 | 93.56 | Quiet and normal.

TABLE XI1.—Readings of thermometers, July 3. Day after transportation of bees.

Thermometer. |
= |
Hour. a | b c d € Observations.
[EZR oll Se a a are
| ° (62 ° F. ° re: ° im ° C ° F ° @ | ° F ° (G: ° F
7.30 a. Mm. . 33.8 | 92.84 | 34.0 | 93.20} 34.0 | 93.20 | 33.6 | 92.48 | 33.0 | 91.40 .
8.30 a. m.. 33.8 | 92.84 | 33.8 | 92.84 | 34.0 | 93.20 | 33.4 | 92.12 | 33.0 | 91.40 | Cloudy.
tOasmen=s- 33.8 | 92.84 | 34.0] 93.20] 34.0} 93.20] 33.4 | 92.12] 33.6 | 92.48 | Breeze.
Ase a 34.0 | 93.20} 34.0 | 93.20} 34.0 | 93.20 | 33.4] 92.12 | 33.4 | 92.12
12m 34.0 | 938.20 | 34.2) 93.56 | 34.2) 93.56 | 33.6} 92.48 | 33.4 | 92.12
7619), 18812 Sona 34.8 | 94.64 | 34.8] 94.64 | 34.6 | 94.28] 34.2] 93.56 | 34.0 | 93.20] Bees returned.
Sipaimeeese | 34.8 | 94.64 | 34.6 | 94.28 | 34.6 | 94.28 | 34.0 | 93.20 | 34.0 | 93.20

O

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

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