Bees/raw chicken
© Quinn McFederick/UCR
Raw chicken baits attract vulture bees in Costa Rica
They might not sting, but there is nothing sweet about flesh-eating vulture bees.

Many entomologists will tell you that bees are basically wasps that became vegetarian, but a little-known species of tropical stingless bee, Trigona hypogea, has evolved to have a particular taste for raw flesh. They even have a special meat-chewing tooth, winning them the charming name of "vulture bees".

Now, a paper published in mBio, also describes how the vulture bees have the omnivorous microbiome to match, including familiar bacteria in sourdough, and even take home meaty leftovers.

"These are the only bees in the world that have evolved to use food sources not produced by plants, which is a pretty remarkable change in dietary habits," says entomologist Doug Yanega from the University of California (UC), US, who was involved in the study.

The concept of "we are what we eat" doesn't apply to most bees. Honeybees, bumblebees and stingless bees have only five core microbes that help them with their vegetarian diet.

"Unlike humans, whose guts change with every meal, most bee species have retained these same bacteria for over roughly 80 million years of evolution," says co-author Jessica Maccaro of UC.

However, flesh-eating vulture bees happen to love a good (raw) chicken dinner, so the researchers asked whether they had microbiomes more similar to other omnivores than their vegetarian cousins.

Meat trap and takeaway

To answer this, the researchers journeyed to Costa Rica, where the bees live, and set up baits - fresh pieces of raw chicken suspended from branches and smeared with petroleum jelly to keep the ants off. With the sneaky treat in place, the vulture bees feasted.

Surprisingly, the researchers observed that the bees were keeping leftovers in tiny structures on the back of their legs that are ordinarily used for collecting pollen. "They had little chicken baskets," says co-author Quinn McFrederick of UC.

The gut microbes of vulture bees are similar to hyenas

The team then compared the microbiomes of meat-eaters to other bees that only ate pollen and found that the vulture bees have much more extreme microbiomes. McFrederick explained:
"The vulture bee microbiome is enriched in acid-loving bacteria, which are novel bacteria that their relatives don't have. These bacteria are similar to ones found in actual vultures, as well as hyenas and other carrion-feeders, presumably to help protect them from pathogens that show up on carrion."
One of these bacteria is Lactobacillus - found in many fermented human foods like sourdough - and flesh-digesting Carnobacterium. Maccaro said:
"It's crazy to me that a bee can eat dead bodies. We could get sick from that because of all the microbes on meat competing with each other and releasing toxins that are very bad for us."
But their weird habit for KFC takeaway isn't the only unusual thing about vulture bees. Yanega said:
"Even though they can't sting, they're not all defenceless, and many species are thoroughly unpleasant. They range from species that are genuinely innocuous to many that bite, to a few that produce blister-causing secretions in their jaws, causing the skin to erupt in painful sores."
Honey, anyone?

And for those who are particularly adventurous, they do still make edible honey. And don't worry, they practise good food hygiene. Maccaro explained:
"They store the meat in special chambers that are sealed off for two weeks before they access it, and these chambers are separate from where the honey is stored."
The team plan to research the vulture bee microbiomes more, to learn how microbes play a role in bee health.
"The weird things in the world are where a lot of interesting discoveries can be found. There's a lot of insight there into the outcomes of natural selection."