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INTRODUCTION.
The common name comes from the fact that these are solitary and not social bees, and that
they usually nest in the ground while some use natural cavities. These solitary bees can
become urban nuisance pests when they nest in large numbers near structures, and they can
sting. They are found throughout the United States. This discussion will be restricted to
those species of these 3 families which nest in the ground.
RECOGNITION.
All 3 families composed of small to medium-sized bees with females and males about
1/8-3/4" (4-20 mm) long; females usually 1-2 mm longer than males of same species.
Color usually dark, some metallic, some with pale bands. Front wing with 2 or 3
submarginal cells. Hind wing with jugal lobe (lobe on rear margin near body) longer than
submedial cell. Additionally -
Andrenidae. Head with 2 subantennal sutures (impressed lines)
below each antennae socket; glossa (tongue middle structure) short, pointed. Front wing
with basal vein straight or nearly so. Color usually dark brown to black, some species
with abdomen banded with pale hair and/or pale hair on body.
Colletidae. Head with 1 subantennal suture (impressed line)
below each antennae socket; glossa (tongue middle structure) short, bilobed or truncate.
Front wing with basal vein straight or nearly so. Color brownish with abdomen banded with
pale hairs, or black and relatively bare with yellowish/whitish areas on face.
Halictidae. Head with 1 subantennal suture (impressed line)
below each antennae socket; glossa (tongue middle structure) short, pointed. Front wing
with basal vein strongly arched. Color of some species partly or entirely metallic green,
blue, brazen, or cuperous.
SIMILAR GROUPS.
Digger bees (Anthophoridae, subfamily Anthophorinae) have front wing
with 2nd submarginal cell shorter than Ist, hind wing with jugal lobe (lobe on rear margin
near body) shorter than submedian cell, and robust and hairy.
Cuckoo bees (Anthophoridae, subfamily Nomadinae) have hind wing with
jugal lobe very small and rounded, and often with whitish/yellowish markings.
Leafcutting bees (Megachilidae) have front wing with 2 almost
equal-sized submarginal cells, hind wing with jugal lobe shorter than median cell, pollen
carried on underside of abdomen.
Honey bee (Apis mellifera) with hairy eyes, hind tibia lacks apical
spurs, and usually orange brown.
BIOLOGY.
These are solitary bees which do not live in colonies. Adults are queens or males.
Andrenid bee burrows are made in the ground, usually consisting of a long vertical tunnel
with lateral branches off of this tunnel to each cell. Sometimes large numbers of these
bees will nest close together, particularly in bare-ground areas. They provision each cell
with pollen and nectar. Both sexes overwinter in the nests.Colletid bees nest in various
natural cavities or in the ground. Their burrow often consists of a straight tunnel with
several short branches at its end containing multiple calls. Cells are provisioned with a
mixture of pollen and nectar. Halictid bees resemble andrenids in nesting habits.
Sometimes large numbers nest close together, often sharing the same tunnel to the outside.
Developmental time (egg to adult) can be about 2 weeks. Sweat bees (genus Halictus) are
sometimes a nuisance when they are attracted to perspiration as a moisture source. They
can give a mild sting, especially when being brushed away.
HABITS.
Andrenid and halictid bees have a habit of nesting in large numbers in the limited bare
areas found around the foundation or in the yard. Some members of the halictid bee genera
Halictus and Lasioglossum are called sweat bees because they are attracted to perspiring
skin. Although they are usually just a nuisance, they can give a sharp mild sting
especially when being brushed away. All of these bees visit various flowers for both
pollen and nectar. Some species are very important pollinators of agricultural crops, such
as the alkali bee (Nomia melanderp, Halictidae) on alfalfa in the Pacific Northwest.
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