POLLEN 
659 
grains is also very variable but is usually 
large. Each anther of the peony has been 
estimated to produce 21,000 grains; and 
if there are 174 stamens to a flower there 
would be 3,654,000 grains. In wistaria 
there are said to be 7000 grains to each 
ovule. The excess of pollen is thus so 
large as to permit of much waste. In 
shape the grains may be globular, ellipsoi¬ 
dal, polyhedral, or of the form of a dumb¬ 
bell in the borage family; or in some 
Polygalaceae they have the shape of “a 
wickerwork basket.” The outer coat may 
be banded, ribbed, or checkered, and beset 
with sharp teeth, points, spines, prickles, 
or knobs; variation in the sculpturing is, 
indeed, almost endless. The air in the nu¬ 
merous little pits and hollows on the sur¬ 
face of the grains protects them from con¬ 
tact with water. The projections enable 
them to adhere to insects. While yellow is 
the prevalent color, red, blue, brown, and 
green hues also occur. 
THE BEHAVIOR OF BEES IN COLLECTING 
POLLEN. ' 
The behavior of bees in collecting pollen 
is of great interest to both beekeepers and 
fruit-growers. Bees are the only insects 
which feed their brood on pollen, to obtain 
which in sufficient quantities they are com¬ 
pelled to visit a great variety of flowers, 
and incidentally are thus most valuable 
agents in pollination. The small primitive 
bees of the genus Prosopis 
have nearly smooth bodies, 
'and the pollen-brushes on 
the hind legs are so feebly developed that 
they are little better adapted for carrying 
pollen than the wasps." The common ground 
bees of the genera Halictus and Anclrena 
show a much greater advance. The body 
is hairy, and the hind legs are entirely 
covered with collecting hairs, which become 
filled with loose, dry pollen grains. A fur¬ 
ther step in the development of the pollen¬ 
collecting apparatus of the hind legs was 
the acquisition of the habit of moistening 
the pollen with honey. Among the solitary 
bees, Macropis and the Panurgidae carry 
in this way large balls of damp pollen 
moistened with freshly gathered nectar. 
Finally among the bumblebees and honey¬ 
bees there occur on the hind legs structures 
called corbicul® or pollen-baskets in which 
the damp pollen is packed, while the tarsal 
brushes are highly specialized. In honey¬ 
bees the tibial spurs on the hind legs, used 
by the wasps and solitary bees in digging 
holes in the ground, have been lost because 
no longer useful. 
In another series of bees the Megachili- 
dae, or leaf-cutting bees, the pollen-collect¬ 
ing hairs form a stiff brush on the under 
side of the abdomen. These hairs slant 
backward and vary in length and color in 
the different species. As the bees crawl 
over level-topped flowers!, like the sun¬ 
flower and other species of Compositae, 
which have a large amount of free pollen 
on the surface, the abdominal brush be¬ 
comes filled with dry pollen. The leaf¬ 
cutting bees are also very common visitors 
to leguminous flowers, as the vetches and 
clovers, which have an apparatus for plac¬ 
ing pollen on the underside of the bodies 
of insects. This large family of bees has 
become adapted to collect pollen chiefly 
from these two groups of flowers. None 
of the species moistens the pollen with 
honey. 
The behavior of the honeybee in collect¬ 
ing pollen has been carefully investigated 
Fig. 1.—Left fore leg of a worker bee. — Bulletin 
No. 121, Bureau of Entomology. 
and described by Casteel. (“Behavior of 
the Honeybee in Collecting Pollen,” D. B. 
Casteel, Bur. Ent., Bull. 121.) Honeybees 
collect pollen from flowers by the aid of 
the mouth parte, the three pairs of legs, 
and the dense coat of long plumose hairs. 
