BUMBLEBEES 
175 
spin their cocoons, the queen begins to 
build a row of cells along the outer edge of 
one side of this cluster parallel with the 
central groove, and later a second row on 
the other side of the cluster. She then lays 
a variable number of eggs, but usually 
from six to twelve in each cell. As soon 
as the workers become sufficiently numer¬ 
ous to provide supplies for the colony the 
queen no longer leaves the nest and may 
lay a new lot of eggs daily. The history of 
the eggs in the later cells is similar to 
those in the first cell except that the larvae 
are fed largely or wholly by the woi’kers 
and the cluster of cocoons is convex with¬ 
out a central groove. The structure of 
the cocoon clusters varies with different 
species. Those of the English Bombus 
terrestris are loose and irregular, while 
those of B. agrorum are compact and glob¬ 
ular and are arranged symmetrically in a 
ring around the nest (Fig. 3). Under¬ 
ground species may protect the top of the 
comb by a roof of wax; but this in sur¬ 
face dwellers is reduced to a mere disc or 
is entirely wanting. On very hot days the 
nest is ventilated by one or more workers 
standing on the comb or in the entrance 
and rapidly fanning with their wings. 
Night brings no rest to the colony. Its 
activity even increases, for now the entire 
population are at home and busily engaged 
in caring for the brood and comb (Fig. 4). 
Pollen is never put in cells containing 
honey, but is stored in empty cocoons or in 
tall columnar cells, which may be over an 
inch high and half an inch in diameter, 
near the center of the nest. A few species 
store it in little pockets on the side of the 
wax-covered bunches of larvae, called by 
Sladen pocket-makers to distinguish them 
from the pollen-storers. The workers 
gather the pollen and load it in the pollen- 
baskets in the same manner as described 
for the honeybee. 
The culminating event in the history of 
a bumblebee colony is the production of 
males and queens, for it is upon this act 
that the life of the species depends. This 
is not undertaken until the old queen has 
laid from 200 to 400 worker eggs, accord¬ 
ing to the species, and the colony is in a 
high state of prosperity. Both sexes may 
occur in the same cluster of cocoons, or it 
may consist wholly of males or females. 
In exceptional cases a colony produces ex¬ 
clusively males or queens. The males ap¬ 
pear earlier and are about twice as numer¬ 
ous as the females. One hundred to five 
hundred males and queens may be raised, 
according to the strength of the colony. 
As in the case of the honeybee the bumble¬ 
bee queens are probably fed on a different 
kind of food than the workers, altho no 
difference has yet been observed. The 
males live for about three weeks, and, like 
the queens, after once leaving the nest sel¬ 
dom return. 
With the departure of the males and vir¬ 
gin queens from the nest, the purpose of 
the colony has been attained in providing 
for the continuance of the species another 
year, and the closing days of its existence 
are now fast approaching. The old queen 
begins to fail, her body becomes denuded 
of hair, and her productiveness decreases. 
There are not sufficient eggs to keep the 
colony busy, and laying workers appear, 
which, however, produce only males. Fi¬ 
nally brood-rearing ceases, and the comb 
begins to mold. There is no longer an 
abundance of flowers, and the surplus of 
honey is consumed: then the older workers 
die one by one and the dozen or more re¬ 
maining become idle. “One night, a little 
cooler than usual,” says Sladen, “finding 
her food supply exhausted, the queen 
grows torpid, as she has done many a time 
before in the early part of her career, but 
on this occasion, her life work finished, 
there is no awakening.” 
There are 47 species of bumblebees 
known in America north of Mexico, and 40 
species in Amei’ica south of Mexico, one 
species ( B. dahlbomii) being common on 
the Straits of Magellan. A large and com¬ 
mon species east of the Rocky Mountains is 
Bombus americanorum , which has a tongue 
14 mm. long (Fig. 5). The colonies live in 
deserted mouse-nests both underground 
and on the surface. B. fervidus is another 
common species found in nearly every 
State in the Union and in Canada (Fig. 6). 
This species is a surface dweller, and its 
nests may be found in a variety of loca¬ 
tions. Putnam found on July 27 a nest of 
paper and rags under the floor of-a shed, 
which contained 70 bees, 150 cells with 
brood, and 200 larvae in various stages of 
growth in the pollen masses, besides 50 
