Bumble Bee Brigade

Since the listing of the rusty patched bumble bee by the US Fish & Wildlife Service (FWS) in 2017, bumble bee interest has grown amongst land managers in the upper Midwest.  As it turns out, some of the best places to find the rusty patched bumble bee are in native prairies that have blooming flowers throughout the entire growing season.

Since the listing of the rusty patched bumble bee by the US Fish & Wildlife Service (FWS) in 2017, bumble bee interest has grown amongst land managers in the upper Midwest.  As it turns out, some of the best places to find the rusty patched bumble bee are in native prairies that have blooming flowers throughout the entire growing season. In this post, Chris Kirkpatrick (TPE) and Susan Carpenter (UW Arboretum) describe a monitoring program to learn more about this imperiled species.

It is not surprising that some of TPE's protected sites are now known to host the rare bumble bee. Last summer TPE partnered with the US FWS and the UW Madison Arboretum to conduct bumble bee training for citizen scientists and agency professionals on how to photo document bumble bees. The goal was to search TPE owned properties, initially those in the Madison, WI area, for bumble bees with the hopes of finding a new population of rusty patched bumble bees. To our amazement, Jeb Barzen, site steward for TPE's Foxglove Savanna documented a new rusty patched population.
 
With hopes of understanding more about this rare bumble bee, TPE is partnering with the UW Madison Arboretum again this summer and would like to train more volunteers to look at TPE sites throughout southern Wisconsin & Minnesota and northern Illinois. Susan Carpenter with the Arboretum will be hosting the training on Monday July 2, from 12:30-3:30pm. The training will be free and open to TPE members on a first come first serve basis with a limit of 20 participants. To register please call TPE's office at 608-638-1873 or email executivedirector@theprairieenthusiasts.org.
 
Participants will be trained to use the WI DNR's new Bumble Bee Brigade monitoring project that launched this month. Anyone can submit photos to Bumble Bee Brigade: http://wiatri.net/inventory/bbb/. The bumble bees have already begun to get very active over the month of May. Susan Carpenter has provided us with an excellent update about bumble bee behavior and how to observe bumble bees this spring and early summer.
 
Timing: The long-term average date of first bumble bee emergence for our area is April 14. This year, because of the late spring, the first new bumble bee new queen sightings were delayed 8-10 days later than that. (Most, if not all, of the early reports were Bombus bimaculatus, the two-spotted bumble bee, which is usually our earliest species to emerge. Other species from early season reports:  B. impatiens, common eastern bumble bee; B. vagans, half-black bumble bee; B. ternarius, tri-colored bumble bee; B. auricomus, black and yellow bumble bee; and B. griseocollis, brown-belted bumble bee. Additional species reported in Wisconsin as of May 28, 2018 are: B. affinis, B. insularis, B. fervidus, B. rufocinctus and B. terricola.
 
The first 2018 report of a rusty patched queen was on May 2, in Lafayette County. It was feeding on oranges put out for orioles. This was the FOY (first of year) record for rusty patched bumble bee and a new county record for Lafayette Co. (https://bugguide.net/node/view/1515646).  Watch for more rusty patched bumble bee new queens now, as they provision their nests, and raise the first cohort of workers. A few workers of other species have been reported so far this season.  
 
Appearance: Bumble bee queens are relatively large bees. They hatched and mated late last summer/fall and overwintered individually underground in several inches of soil. Rusty patched queens have black pile (hairs) at the head, and yellow pile with (usually) a black spot on the thorax. The first two abdominal segments are yellow, with no rusty patch. The remaining abdominal segments are black. For definitive IDs, be sure to take multiple photos of the abdomen of the bee and top and front of the head, as there are other species that could be mistaken for rusty patched at this time of year.
 
Behavior: After emergence, the new queens have to search for a suitable nest site and find pollen and nectar sources.  Nest sites are generally underground (in an animal burrows, cracks in rock walls, hollow logs, cracks in foundations, etc.). You will often see them flying close to the ground back and forth across an area, sometimes landing to walk down under leaf litter or into a hole. She could be exploring the location or she may have established the nest. If you see a queen carrying pollen into the hole or cavity, she is already provisioning the nest. At first, she is the only bee coming and going from the nest, and you may not see her often. There are relatively few queens overall (compared to the number of bees seen later in the season when the colonies are larger). It takes several weeks for the first group of workers to develop and fly from the nest, so you will see workers (with a rusty patch on the 2nd abdominal segment) in late May or June. (As of May 28, there are no reports of rusty patched workers.) In extreme heat, bumble bees may be active early and late in the day, rather than mid-day.
 
Habitat: Because the queens have to locate pollen and nectar immediately after emergence, they are found then on early flowering native species: willow (Salix spp.), plums and cherries (Prunus spp.), Juneberry (Amelanchier spp.), leatherwood (Dirca palustris), gooseberries (Ribes sp.), prairie smoke (Geum triflorum), shooting star (Primula meadia), wood betony (Pedicularis canadensis), and woodland wildflowers like Dutchman's breeches (Dicentra cucullaria). Bumble bees also forage on ornamental cherry, crabapples, and apples, and on weeds such as creeping Charlie (Glechoma hederacea), dead nettle (Lamium amplexicaule), mustards, and dandelion. As of May 28, they have been foraging on wood betony (Pedicularis canadensis), woodland wildflowers like Virginia waterleaf (Hydrophyllum virginianum), Ribes species, Rubus species, Rosa species, spiderwort (Tradescantia ohioensis), Baptisia species, wild lupine (Lupinus perennis), and ornamentals like horsechestnuts (Aesculus hippocastanum) and Azaleas.
 
Documenting (photographing) bumble bee queens on short plants is easier than on trees or shrubs, where it can be more challenging to get definitive photos. When looking for queen bumble bees, search patches of floral resources to see how many and which bumble bee species are present.
 
Photographs contributed by Jeb Barzen, Randy Schindle, and Jerry Newman.


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