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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Be careful with bumble bees, Bombus spp.


Gathering pollen is the name of the game for this hairy lady.


Bees are critically important to agriculture around the globe. Bees provide the vital service of pollination for some of our most important crops including  apples, blackberries, citrus, almonds, cotton, soybeans, sunflowers, clover, asparagus, broccoli, carrots, cucumbers, eggplants, lima beans, onions, peppers, pumpkins, cantaloupes, and watermelons just to name a few. The economic benefit provided by our buzzing friends is estimated to exceed 20 billion dollars annually in the United States. If we set aside the honey bee, an insect not native to this country, one has to wonder how all of the flowering plants were pollinated in North America before the arrival of the honey bee with colonists just a few centuries ago. The answer is that many of our native pollinators, including bumble bees, were and continue to be responsible for pollinating many cultivated crops and uncultivated flowering trees, shrubs, and herbaceous plants gracing our gardens, fields, and woodlands.

There are about 49 species of bumble bees known to occur in the United States. As with many pollinators, there is growing concern that this number is declining. For example, the Franklin bumble bee, once widespread in many western states, has not been seen recently in several locations where it was once common. Introduced pathogens, pesticides, and habitat loss and deterioration are thought to contribute to the decline of our native pollinators, including bumble bees. Recently, a bumble bee kill estimated at 50,000 was reported in a parking lot in Oregon when a systemic insecticide was applied to linden trees in an attempt to control aphids. The Xerces Society reports that this is the largest mass death of bumble bees recorded. To read this report, please click on the following link (

Cone flowers are excellent attractors for bumble bees.


 In my corner of the world, this has been a remarkable year for bumble bees. During the past few weeks a burgeoning number of bumble bees dined at my salvia, cone flowers, bee balm, and coreopsis.  In puzzling over this renaissance, I decided to tail one of the workers and discovered a bumble bee nest in the lawn at the rocky margin of the flower bed - lucky me! These gentle giants of the bee world allowed me to record their comings and goings for this episode. While they will defend the nest and themselves if absolutely necessary, my experience in photographing and interacting with these bees reveals that they are among the most docile of the species.

Bumble bees sometimes build nests in man-made structures like wall voids.

Bumble bee nests are usually constructed in an abandoned burrow of a ground dwelling rodent, such as a mouse or a shrew. Often these occur in fallow fields, but in my case the nest appeared to be coincident with a vacant chipmunk burrow. Bumble bees sometimes construct nests in manmade structures, including wall voids and dryer hoses. They will colonize hive boxes as well and are very useful in pollinating greenhouse crops. In our area, bumble bee colonies are founded by single female queens that have survived the rigors of the Maryland winter in protected locations outdoors. Early in the spring, the queen begins construction of the nest by building wax cells in which eggs will be laid and larvae will be reared. Larvae eat pollen and honey collected and produced by the queen first and later by the workers.

During the growing season, workers industriously gather nectar and pollen to feed the brood back in the nest. Pollen and honey are stored in separate chambers within the nest. Unlike their honey bee relatives, bumble bees do not store large amount of honey in the nest. Honey bees provision their colony to survive the lean winter months when nectar and pollen cannot be collected. Bumble bees have no need to store vast reserves as only the mated queens survive the winter in the quiet solitude of hibernation. These founding mothers initiate new colonies in spring. 

A vacant chipmunk’s burrow is the perfect spot for a bumble bee nest.


If you must use insecticides in your garden or landscape, always read the label carefully and heed warnings particularly as they relate to bees. Many of our newer insecticides have systemic activity within plants and, although they may be applied to the soil, they may still wind up in nectar and pollen.  Insecticide-laced nectar may be devastating to pollinators and other beneficial insects. It is a good idea to avoid using these products when plants are in bloom and being visited by pollinators. So, as you enjoy your flowering trees, shrubs, and herbaceous plants this summer, take special care of your pollinators, including bumble bees.


We thank Dave Inouye for providing the image of the bumble bee nest. To learn more about bumble bees, please visit the flowing web sites: