Why Do Bumblebees Have Stripes?

If you've ever seen a bumblebee rummaging clumsily in the garden, you'll know those aren't racing stripes. The genus bombus is known neither for grace nor speed.

But what you may not have known is that those stripes come in hundreds of different patterns. You'd be forgiven for not taking a closer look. Even though bumblebees aren't the stinging type — only females even have stingers and they're reluctant to use them — these little buzzing balls can seem a little intimidating.

Researchers at Penn State University, however, recently took a closer look and they discovered a remarkable amount of variation from one bee to another.

"There is exceptional diversity in coloration of bumblebees," lead author and biologist Heather Hines noted in a press release. "Of the roughly 250 species of bumblebees, there are over 400 different color patterns that basically mix and match the same few colors over the different segments of a bee's body."

At the heart of all that diversity, biologists isolated — for the first time — genes that control the color patterns for every species of bumblebee. But why, you might ask, should a bumblebee require such nuance? What do those stripes really do for them?

Well, it may be more about what they do for us. Despite the hundreds of patterns and shades found on bumblebees, they tend to reserve a different color for the region around the tail. That would, of course, be where the stinger resides, at least among females.

A colorful warning label

As noted, bumblebees don't like to go on stinging sprees. To save them — and us — the trouble, they offer a convenient warning label around the bee's business end.

Researchers noted that bumblebees, like many animals, utilize eye-catching patterns to let potential predators know that they're packing heat.

The pudgy pollinator doesn't even have to be armed with a stinger. But, thanks to a phenomenon known as Müllerian mimicry, it waves the same patterned flag. After all, if predators have long been conditioned to associate certain colors with toxicity, why shouldn't even relatively delicious animals and insects shelter under their protective banner?

"Through processes like mimicry, these bees have undergone an exceptional natural radiation, exhibiting hundreds of different body color patterns across the globe," Hines noted in a 2015 release.

The pattern-controlling genes in bumblebees, called "Hox genes" act as "blueprints for the segments of a developing bee larva." Those blueprints, the research suggests, are passed onto larva at a late stage in development, meaning they could be tailored to a specific environment.

Bumblebees living in different regions may have different coloration because the visual language of danger is different. So, for instance, bumblebees in the eastern U.S. will have predominantly yellow and black bands. But closer to the Rocky Mountains, they add a bright orange band to the yellow and black.

Those patterns ensure that, no matter where a bumblebee lives, it doesn't have to be the swiftest or the most graceful flyer. It can, in fact, go about its pollinating business as slowly and lazily as it likes — because no one is going to mess with a winged mini-bus with a bumper sticker that reads: You'll be sorry.