In a previous episode of Bug of the Week, we learned the plight of the honey bee, Apis mellifera, as it battles the dark forces of CCD – colony collapse disorder. 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. The economic benefit of our buzzing friends is estimated to exceed 14 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 the plants were pollinated in North America before the arrival of the honey bee with colonists just a few centuries ago. The answer is that humble bees, a.k.a. bumble bees, were and continue to be responsible for pollinating many cultivated crops and uncultivated trees, shrubs, and herbaceous plants in our gardens, fields, and woodlands. Bumble bees are critically important in the production of those delicious December tomatoes grown in greenhouses around the world. During the past weeks bumble bees have been remarkably abundant on the flowering perennials, cucumber blossoms, and squash flowers in my gardens. In late summer and autumn workers franticly gather nectar and pollen to feed the brood back in the nest.
Bumble bee nests are usually constructed in an abandoned burrow of a ground dwelling rodent such as a mouse or a shrew. Fallow fields and forest edges are excellent habitats for bumble bees, however they can be enticed to construct nests in special hive boxes and have been reported in wall voids and dryer hoses. In our area, bumble bee colonies are founded by single female queens that survived the rigors of Maryland’s winter in protected locations outdoors. Early in spring, the queen initiates a nest by moving into a cozy rodent burrow, building a waxen pot to store honey, provisioning a second chamber with pollen, and laying several eggs within in the brood
chamber which is then sealed.
Eggs hatch into larvae that eat the pollen. These larvae will become the entourage of workers that will later aid the queen in feeding and caring for their sisters as the colony increases in numbers during the spring and early summer. Late in summer the queen lays eggs destined to become the queens. Unfertilized eggs develop into male bees, the drones. The old queen and her workers die near the time of the hard frost and the new queens abandon the nest to find protected refuges to spend the winter. Unlike their honey bee relatives, bumble bees do not store vast reserves of honey in the colony. Within the nests of honey bees, thousands of workers and the queen must survive a season with no nectar or pollen. Honey bees provision their hives with honey to survive the lean winter months. Bumble bees have no need to store vast reserves as only the queens survive the winter outside of the nest. 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, a resident of Oregon and California, has not been seen recently in several locations where it was once found. Introduced pathogens, pesticides, and habitat loss and deterioration are thought to contribute to the decline of our native pollinators including bumble bees. One way to help conserve these marvelous creatures is to use pesticides sparingly or not at all near flowers where these bees humbly forage.
Two wonderful references “Insects: Their Natural History and Diversity by Stephen Marshall” and Status of Pollinators in North America by the National Research Council were used as sources of information for this bug of the week. We give special thanks to David Inouye for providing images for this week’s story. For more information on native pollinators including bumble bees, please visit the following web site.