Bumblebees, Our Native Pollinators

Lee Fields  |  6/9/2017 3:19:22 PM

One of the joys of summer gardening is watching insects flitting from flower to flower. Bumblebees are fascinating as they literally bumble along visiting flowers. They don’t seem to mind being looked at closely as they continue along their way. I have read that they sting only defending their nest. Unlike the non-native honey bee a bumblebee can sting multiple times but they are not considered aggressive.

Bumblebees are one of our native bees. There are 250 species of bumblebees reported worldwide and about 50 North American species. Of those, 9 species are found in Louisiana. In my backyard I only find one species, Bombus impatiens, the common eastern bumblebee. I confess to being a novice to bee identification. Bumblebees who live with me have a black fuzzy abdomen. I am using information provided by the Xerces Society. Bumblebees are easy to see and make a loud buzzing noise when present in large numbers. They are fairly large and definitely hairy. Color and arrangement of the hair on the abdomen is a primary identification tool. As they go about they collect pollen on their hind legs in structures known as pollen baskets or corbiculae.

Most of our native bees are solitary not so, the bumblebee. Typically, these bees live in nests of 25-200 bees. I noticed there seem to be only a few bumblebees in early spring. Last year I worried about where they had gone, fearing someone had sprayed something toxic in my area. Then, I read the bumblebee queen is the first to emerge in early spring. She forages for nectar and pollen taking it back to her nest. She will be the only early bumblebee observed. In her nest she prepares wax cells for the eggs. She forages for nectar and pollen to nourish the larvae as they hatch. Initially all work is done by a single queen who also keeps the larvae warm by shivering above the developing larvae providing warmth. After about a month the hatchlings develop into female workers who then collect pollen and nectar while the queen continues to lay eggs. In late summer some of the eggs will not be fertilized; these eggs develop into males. The only job of the male bumblebee is to fertilize new queen bumblebees who also form in late summer. Sadly, the entire colony including the old queen dies with the onset of cold weather. Only fertilized queen bees survive. These survivors find protected places to overwinter such as holes or under leaves (a good excuse not to rake).The arrival of spring begins the process anew.

The important thing about bumblebees is they are excellent pollinators. Sometimes we think the honeybee is our principle bee pollinator, but many native bees are efficient pollinators. In return for pollinating our plants the bees take away food in the form of nectar and pollen (protein source).

Bumblebees have the ability to buzz pollinate. Flowers such as tomatoes release pollen when vibrated. Bumblebees grab the anther of these flowers and vibrate flight muscles at about the frequency of middle C causing pollen release.

Bumblebee species are declining worldwide. So, what can we do to help them survive? Efforts in any garden can have positive results for our bumblebees. In my small corner of North Louisiana bumblebees visit salvia (Salvia spp.), gaura (Gaura lindheimeri), hyssop (Agastache foeniculum), and althea (Hibiscus syriacus). Many different flowers can provide pollen and nectar for these bees since they are considered generalists. Bumblebee survival can be improved if we provide flowers they visit for nectar and pollen. This article was contributed by Donna White, Lincoln Parish Master Gardener.

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