Bee Byte: Bombus franklini

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Endangered. Social. Narrow Range.

 

Map made via DiscoverLife; modified to most closely resemble Williams, Thorp, Richardson, and Colla (2014)
Map made via DiscoverLife; modified to most closely resemble Williams, Thorp, Richardson, and Colla (2014)Status: Critically Endangered, last recorded by Robbin Thorp in 2006

Status: Critically Endangered, last recorded in 2006 by Dr. Robbin Thorp

Name: Franklin Bumble bee

Family: Apidae (with: honey bees, carpenter bees)

States: Oregon and California

B. franklini has experienced a sharp decline since 1998, and has not been spotted in the wild for over a decade, earning itself a spot on the critically endangered species list and a spot as the Bee Bytes mascot. It also has one of the most narrow distributions for a bumble bee in the world.

The yellow half of the thorax (closer to the head) with an inverse U shape in black can be used to differentiate it from the similar looking B. occidentalis. 

Photo credited to Dr. Robbin Thorp
Photo credited to Dr. Robbin Thorp

Like other bumble bees, B. franklini are social; they live in colonies with a queen, who reproduces, and her daughters, who gather nectar and pollen. The colony does not overwinter. B. franklini are generalists, meaning they can use a variety of flowers for food; like all bumble bees, they are buzz pollinators, vibrating at a high frequency to dislodge pollen from the flowers’ anthers.

A potential cause of B. franklini decline is the fungal pathogen Nosema bombi, which has been found with increasing prevalence on museum specimen from declining populations. It is possible exotic strains were introduced from Europe, due to the American agricultural industry’s use of bumble bees reared in Europe to pollinate crops.

These bees are ground-nesters, thought to live in abandoned rodent burrows in grassy meadows. A paucity of research on B. franklini means little is known about the species, making conservation efforts more difficult.

More resources on the species and its decline:

NPR: The Bumblebee Hunter

ICUN Redlist Entry

Test of the invasive pathogen hypothesis of bumble bee decline in North America

Evidence for decline in eastern North American bumblebees (Hymenoptera: Apidae), with special focus on Bombus affinis Cresson

Bumblebees of North America: An Identification Guide by Paul Williams, Robbin Thorp, Leif Richardson, Sheila Colla (2014; Princeton University Press).

 

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