common name of bumble bee possibly comes from their rather
large, clumsy appearance and/or the buzzing sound they make
as they fly. In the urban setting, bumble bees do not usually
nest in structures but are of concern because of their abundance
around the many flowering plants typical of yards, and because
they can sting. There are about 51 species (45 in Bombus,
6 in Psithyrus) in the United States and Canada, and as a
group they are found throughout the United States.
worker body length about 1/4-1" (6-25 mm), queens about
3/4-1" (17-25 mm) long; robust in form. Color black with
yellow (rarely orange) markings; with overall fuzzy appearance,
including top surface of abdomen. Head with distinct space
between base of compound eye and base of mandible. Hind tibia
with apical spurs. Front wing with 2nd submarginal cell more
or less rectangular, about as long as 1st submarginal cell.
Hind wing lacks a jugal lobe (lobe on rear margin near body).
Stinger relatively smooth, with small barbs.
addition, Bombus with hind tibia modified into pollen basket
(surface bare and polished, marginal hair fringe) whereas,
Psithyrus lacks pollen basket, hind tibia slender.
(1) Carpenter bees (Xylocopa spp.) with top surface of abdomen
largely bare and shining, front wing with 2nd submarginal
cell triangular, and hind wing with jugal lobe (lobe on rear
margin near body). (2) Some robber flies (Diptera: Asilidae)
with only 1 pair of wings. (3) Some hawk moths (Lepidoptera:
Sphingidae) with siphoning mouthparts.
Bumble bees are social insects which live in nests or colonies.
The adults are represented by workers (Psithyrus spp. lack
workers) which are sterile females, queens, and males (drones)
which come from unfertilized eggs and usually appear in late
only inseminated queens overwinter and do so underground.
In the spring, the queens of Psithyrus species wait until
the Bombus nests are moderate in size and then parasitize
them. The Bombus queens select a suitable subterranean cavity
or surface grass clump as a nesting site. Then the Bombus
queen fashions a honey pot of wax scales near the nest entrance
into which she regurgitates nectar. Next she makes a pollen
clump on the nest floor and lays 8-10 eggs on it. The queen
will periodically add pollen and nectar to the peripheral
edges of the clump, and eventually more eggs. Developmental
time (egg to adult) is 16-25 days, with 4 larval molts. Workers
live about 2 weeks. Most first brood workers are small due
to nutrition. The queen will increase the number of eggs laid
as the number of workers to care for them increases.
the summer, parasitism may eliminate up to 50% of the colony's
workers each week. However, a mature bumble bee nest ultimately
contains about 50-400 bees at any given time; the largest
known nest contained 756 bees and 385 brood (larvae and pupae).
nest temperature is regulated to about 86 degrees F (30 degrees
C). This thermoregulation is accomplished by the bee relaxing
the 3rd axillary muscle to its wings which unhinges the wings
from the main power-producing thoracic muscles. Then contractions
of these large muscles produces body heat without wing movement.
the late summer only males (drones) and new queens are reared
in the nest. Once these new queens emerge, they mate and find
a suitable place to overwinter.. The males, workers, old queen,
and any virgin new queens die with the onset of cold weather.
Depending on the Bombus species, the overwintering queen will
select an appropriate nesting site the following spring. The
queen of some Bombus species locate a dark cavity at least
3/4" (2 cm) high by 1 1/8" (3 cm) wide containing
fine plant fiber; such a nest is usually underground and often
an abandoned mouse nest. Queens of other Bombus species select
a dense clump of grass on the surface for a nest, adding grass
on top. The queens of Psithyrus species are all parasitic
on Bombus nests, so they bide their time until the Bombus
nests are moderate in size and can therefore support them.
They then enter the nest, kill the Bombus queen, and take
over the nest using the Bombus workers to care for her young.
Bombus queens of later emerging Bombus species sometimes also
parasitize the nests of earlier emerging Bombus species.
bees foraging for nectar fly at 7-12 mph (11-20 km/hr) and
spend only 2-4 minutes inside the nest between trips. Probably
they will travel at least 3 mi (5 km) if necessary for nectar.
They orientate by the sky's polarized light via their 3 ocelli,
so they can forage before and after light when objects and
landmarks are not visible. They use their thermoregulation
procedure to warm up flight muscles before the sun rises and
to also forage when temperatures are below 50 degrees F (10
degrees C; lowest observed flight at 26 degrees F/-3.6 degrees
C) whereas, most bees stop foraging at 61 degrees F (16 degrees
C). Each worker forages independently, and bumble bees never
exchange food. Old cocoons are used to store both pollen and
nectar. Only enough food (honey and pollen) for a few days
is stored at any given time which helps discourage nest predation
by skunks, foxes, etc.
is usually done by using their relatively smooth stingers
which can be used over and over. Some species will also spray
feces, and some cover the intruder with regurgitated honey.
People sensitive to insect venom should exercise care around
bumble bee nests.
Bumble bees are considered beneficial insects because they
pollinate the flowers of many plant species. However, if their
nest is located in or close to an occupied structure or recreational
area, then control is warranted. During the day find the location
of each nest by observing where the bees disappear into the
ground, grass clump, or structure. At night using background
light and while wearing a bee veil, apply an appropriately
labeled pyrethroid pesticide. Dusts work best when applied
to an area 6" (15 cm) around the nest entrance. For structural
nests, treat with dust or aerosol but do not seal the entrance.
Structural nests should be either retreated with a long-lasting
repellent material and sealed or the void opened up and cleaned
out within 1-2 days to prevent future problems with dermestid
beetles, spider beetles, and/or psocids.