Bug o’the Week – Northern Amber Bumble Bee

Howdy, BugFans,

This one’s dedicated to BugFan John – it was an honor.

The BugLady has been enjoying an abundance of bumble bees on the prairie recently, despite the fact that, along with the start of the tree cricket chorus, it is a sure sign of the impending autumn.

Quick and dirty bumble bee review:

They’re important pollinators.  They are not aerodynamically designed.  Most native bees are solitary, but bumble bees live in colonies headed by a queen, and unlike their solitary cousins, will sting to defend the nest.  Because of their ability to raise the temperature inside their thorax by shivering their wing muscles, they can fly in pretty chilly weather (other insects can do this, too, but bumble bees are the champs, warming from 55 to 98 degrees Fahrenheit in just six minutes).  They deliver ecosystem services and are considered “keystone species” – species whose absence would affect their communities (no bees = no fruits and seeds = no wildlife).  Many bumble bee species are in trouble.  For more details about all that and more, see these previous BOTWs https://uwm.edu/field-station/bumble-bee-redux/https://uwm.edu/field-station/celebrating-bumblebees/, and https://uwm.edu/field-station/rusty-patched-bumble-bee/.

“Bumblebee” or “bumble bee?”  It’s the same rule that governs the names of flies.  The folks at Minnesota Seasons explain: “The Entomological Society of America follows the convention suggested by R. E. Snodgrass, author of Anatomy of the Honey Bee (1910), when assigning common names to insects. Snodgrass states, ‘If the insect is what the name implies, write the two words separately; otherwise run them together. Thus we have such names as house fly, blow fly and robber fly contrasted with dragonfly, caddisfly and butterfly, because the latter are not flies, just as a dandelion is not a lion and a silverfish is not a fish. The honey bee is an insect and is preeminently a bee; ‘honeybee’ is equivalent to ‘Johnsmith.’”

So – the Northern amber bumble bee (Bombus borealis) aka the Boreal bumble bee is a medium-large bee in the bumble-honey-carpenter-cuckoo-digger bee family Apidae.  Called “amber” because it is, and “northern” because its range extends east from the Rockies across Canada and the northern US.  Its former range dipped farther south, even into Georgia at the higher elevations of the Appalachians.

Bumble bees need three habitats that are not too far apart – one for foraging, one for nesting, and one where the queen overwinters.  Northern Amber bumble bees are found in grasslands and agricultural fields near woods.

Their biographies are similar to those of other bumble bees.  Newly-minted queens mate in fall and overwinter on the ground, under cover.  They emerge in late May/early June in Wisconsin (not one of the super-early species) and make a nest that’s usually underground but could be in a rock pile, tree hole, or clump of grass.  South-facing, abandoned rodent burrows are favorite spots, and she often must fend off other queens who have their eyes on the same real estate.

She cares for the first brood herself, feeding nectar (carbs) and pollen (protein) to the larvae, and if it’s chilly, sitting on the eggs and using her thermoregulatory abilities to warm the brood patch on the underside of her thorax (her daughters will later regulate the temperature of the nest).  She hands off the child care, foraging, and nest maintenance duties to them when they become adults (the BugLady read somewhere that individuals in this initial brood may be smaller, because they had only one caregiver).  Populations peak in late summer as a crop of males is produced, but only the new queens will make it through the winter.

Bumble bee species have different tongue lengths, designated as “short,” “medium,” and “long,” and the length of their tongues determines what flowers they feed on.  Of course, some short-tongued bees have devised a “work-around” – making a hole at the base of a tubular flower and lapping nectar from the outside.  Northern amber bumble bees are long-tongued bees, and although you find them on composites and roses, they are able to extract nectar from the tubular flowers of clovers and vetches.

According to the Xerces Society, “more than a quarter of North American Bumble Bees are facing some degree of extinction risk.”  Northern amber populations are vulnerable along the southern edge of its range, especially in the East, but they seem to be stable in Wisconsin.  Minnesota has seen a large shrinkage of territory occupied, with the range shifting northward.

One problem in censusing bees is a phenomenon called “Shifting Baseline Syndrome.”  There are few long-term studies of bumble bees, so today’s scientists are starting in a hole – they’ve never seen the bees at their earlier population levels, and the present, diminished populations are their “baselines.”  There have been some studies of historical bumble bee numbers using museum collections; these searches show a loss both of diversity and of range starting as agriculture intensified in the middle of the last century, and some species are now “locally extirpated” (locally extinct).

Some studies suggest that the bumble bee species that are declining tend to have shorter lists of plants that they forage on, but other factors, like climate, could be contributing.  Like honeybees, bumble bees are an industry, with captive bees carted around the country.  Some of the bumble bees that are contracted out to pollinate greenhouse crops are not native, some carry diseases, and some escape to infect native bees.

How can we help?  Bee-friendly plantings (bee-friendly plantings, bee-friendly plantings), bee-friendly buffers, including hedgerows around agricultural fields and along roads, bee surveys (https://wiatri.net/inventory/BBB/getInvolved/), and fewer herbicides and pesticides.  Since rodent burrows are at a premium, some researchers are experimenting with manmade nest boxes.

Here is more information about bumble bee ID:

https://www.fs.fed.us/wildflowers/features/posters/EasternBumblebeesPoster_reduced.pdf

https://apps.extension.umn.edu/environment/citizen-science/bee-atlas/bumble-bees/docs/bumblebee_species_slides.pdf

https://www.fs.fed.us/wildflowers/pollinators/documents/BumbleBeeGuideEast2011.pdf

Go outside – watch bumble bees!

Kate Redmond, The BugLady