Rusty-patched Bumble Bee (Bombus Affinis)

The Rusty-patched bumble bee or Bombus affinis is endangered in Canada, the United States and critically endangered globally.  It was the fourth common bumble bee in Ontario during the 1970s.  Found in rural wood lots and city ravines and everywhere in-between.  It was a very common species of bumble bee throughout the 1980s in Ontario.  The Rusty-patched bumble bee last know location in Canada was Ontario’s Pinery Provincial Park, but hasn’t been seen in Canada since 2009. 

Rusty patched bumble bee queens are entirely yellow on the first two abdominal segments and the rest of the abdominal segments are black.  Workers and drones rusty-patched bumble bee have rust-coloured patched in the centre of their back. The rusty patch, which is an area of rust-colored hairs, is on the front of the second abdominal segment with yellow hairs on the sides and towards the back of the segment.  They also have distinctively short tongues.  If you do see a rusty-patched bumble bee please take a photograph and upload it to one of these three websites: bumblebeewatch, and/or bumblebee brigade.

The spring brings life to the colony.  The queen bee emerges in early April from diapause.  Diapause is an insect’s version of hibernation.  Insects that enter diapause become dormant in early fall compared to mammals that hibernation after winter has started.  The queen bee starts laying eggs right away, growing her hive till it reaches around 1000 worker bees. The hive is active with bees until late October. A new queen will enter diapause while the old queen, workers and drones die at the end of the year.

The rusty-patched bumble bee is considered a habitat generalist, meaning that it can adapt to a wide range of environmental conditions. It forages from dozens of food plants, including milkweed, sunflowers, clovers and fruit blossoms.  It is responsible for pollinating prairie wildflowers, cranberries, wild blueberries, apples, alfalfa, as well as other crops.  It is estimated that yearly $9 billion worth of crops are pollinated by native pollinators in the United States. 

We don’t have the answers for why the population has weakened to the point it is Critically Endangered globally. At the local level, the use of pesticide and the loss of habitat have contributed to dwindle rusty-patched bumble bees. Other factors may include climate change and infections.

There is an hypothesis that the Rusty-patched bumble bee as well as other bumble bees are being infected with Nosema Bombi from greenhouse bumble bees.  Greenhouses use bumble bees to pollinate their produce.  The greenhouse bumble bees can come and go through the vent system where they can spread Nosema Bombi.  Nosema Bombi is a fungus with two life stages; spore stage and vegetative stage.  The bee ingested the Nosema spore, which infects the cells of the bee’s stomach.  It than keeps spreading internally throughout the bee.  It is believed that it is a Horizontal transmission from contaminated shared food like pollen or nectar.  But there is some prove it may also be Vertically transmitted from a drone to a new queen.

In February 2013, the Xerces Society asked to have the rusty-patched bumble bee listed as an endangered species.  On March 21, 2017 the rusty-patched bumble bee was finally listed by the U.S. Fish and Wildlife as an endangered species, after its population had dropped by almost 90%.   Canada listed the rusty-patched bumble bee as Endangered on Schedule 1 of the Species at Risk Act in 2012.  On December 29, 2014 the rusty-patched bumble bee was placed on the International Union for Conservation of Nature’s Red list as critically endangered

Canada and the United States are planning to help restore habitat and establish breeding programmes in hopes to get the rusty-patched bumble bee off of the endangered species list.  We all need to do our part in insuring another day for these bees and other species at risk.  Let the wildflowers grow at the sides of roads.  Don’t use pesticides and herbicides on your yard.  Let your grass grow before cutting it.  Plant a pollinator garden.