Rusty-patched Bumble Bee, Bombus affinis

Excerpted from Bumble Bees of Wisconsin

Rusty-patched Bumble Bee, Bombus affinis This once common bumble bee is the first federally protected species of bumble bee, and first bee to be placed on the endangered species list.

Physical Description

Hair medium and even. Thorax yellow, with a straight or “T” shaped band of black hair between the wings. First abdominal segment fully yellow, with the second segment yellow and usually containing a patch of orange or rusty-brown hair. Unlike B. griseocollis, this patch is entirely surrounded by yellow hairs. Queens often without the rusty-patch, making the second abdominal segment entirely yellow. Males have similar color patterns to workers, but occasionally with more brown hair on the second abdominal segment. Males also lack corbiculae, or the flattened midleg of the hind leg used for transporting pollen.

Activity Period

Rusty-patched Bumble Bee activity period Queens emerge in late spring (typically early May), with peak worker numbers in July and August. New queens and drones present from July to September.


Rusty-patched Bumble Bee, Bombus affinis graphic Historically, Bombus affinis was found throughout the upper Midwest and Northeastern United States. Its range has been reduced by over 90%, and is now only found in small pockets, with areas around Madison seeing some of the most consistent numbers in recent years. Other recordings include areas in the driftless, near Milwaukee, and near Baraboo.

Preferred Flowers

 Bee Balm

Bumble Bee Videos

 Buzz Pollination
 Slo-Mo Footage of a Bumble Bee Dislodging Pollen
 Look Inside a Bumblebee Nest
 How to Build a Bumble Bee House
 Development of Colony and Nest in the Bumblebee

Bumble Bee Buzz Pollination

Bumble Bee Buzz Pollination

Only Bumble Bees do it! Buzz pollinated flowers wait until a bee comes along and vibrates at just the right frequency and out comes the pollen in a spew.

Bee Quiz Logo

Take The Bumble Bee Quiz

Take this quick quiz and see how much you know about Bumble Bees. This quiz is intended for fun, in a random-facts-can-be-cool kind of way.

Monarch Butterfly Caterpillar

Caterpillar ID Guide

Identify who is nibbling on your native plants. You will find over 30 Wisconsin native butterfly caterpillars.