SOLITARY BEES 
763 
great balls of pollen, half the size of the 
abdomen, are carried on them. The com¬ 
mon genera Anthophora and Melissodes 
visit the same flowers as bumblebees 
(Fig. 4). 
Many bees •with a short term of flight 
visit only one or a few allied species of 
flowers, which are abundant and in bloom 
during the time the bees are on the wing. 
Certain vernal species of Andrena visit 
only the flowers of the willows, while other 
HOST BEES AND GUEST BEES. 
According to the way in which they pro¬ 
vide for their young, bees may be divided, 
into nest-builders and brood parasites. The 
• nest-builders are industrious insects, con¬ 
structing their nests with great care and 
skill, and provisioning them with food for 
the use of the brood. The brood parasites, 
on the contrary, neither build nests nor 
gather stores for their offspring, but in the 
case of the solitary bees they lay their eggs 
6 
Fig. 4.—Long-tongued bees with pollen-brushes on hind legs. Anthophoridae: 1. Antho¬ 
phora smittiu, male. 2. Anthophora nccidentalix. female. 3. Centrix ajAcalis, female. 4. Melis- 
xodes atripes; a, female; b, male. 6, Melixsodes dexsponsa; a, female; b, male. 
at a favorable opportunity in the cells of 
the nest-builders. The latter are often 
called host bees and the former guest bees. 
HABITS OF THE NEST-BUILDING BEES. 
The genus Prosopis, says Knuth, stands 
at the lowest level among bees and belongs 
to them only because it feeds its young on 
pollen and nectar. The female builds a row 
of cells in the hollow stems of blackberry 
bushes from which she has excavated the 
autumnal flying species confine their visits 
to the goldenrods and still others to the 
asters. There are indeed a number of bees 
which obtain their supply of nectar and 
pollen exclusively from the Compositae. 
These flowers, as in the case of the golden- 
rod and thistles, are very common, yield 
ample food supplies and are easy to visit. 
This habit has arisen because of the ad¬ 
vantage thus gained by the bees and is 
called oligotropism. 
