Sweat Bees

These tiny, colourful bees make great pollinators — and they love the taste of human sweat.

I spend a lot of time convincing people that there are other types of bees besides honey bees and bumble bees. In fact, there are thousands of different types of bees in the world, some of them so unique and beautiful that I can’t believe they’re not as famous as the classic honey bee.

As a researcher, I’ve worked with big bees, medium-sized bees, and extremely tiny bees. I’ve run into yellow bees, blue bees, green bees, red bees, and multi-coloured iridescent bees. Bees that look like wasps, bees that look like flies, bees that look like nothing you’ve ever seen before. Bees that are the size of your entire thumb (wingspan of 2.5 inches!) with jaws big enough to bite off your pinky finger. And bees that are so small and fast that you could miss them if you blink.

There are so many different types of bees. But one of my favourites, simply because they are so brightly coloured and tiny, is the sweat bee.

I’m sure you’re thinking — what’s a sweat bee? Maybe you’re picturing that fly that’s always buzzing around your head on a long run, or some kind of bee species you’ve never heard of that drinks human sweat. The truth is you’re not too far off.

When I first started my research, I spent the spring in meadows and parks — I was surrounded by bees. I recognized the big bees, the bumble bees and mason bees, and the common honey bees. I also found many tiny insects, which I recognized as a type of bee from their fuzzy body hair and collection of pollen and nectar in flowers. But I couldn’t place them — they were so small, so brightly coloured, I couldn’t believe they were bees. I started digging into identification of these miniature bees, and what I found surprised me.

Sweat bees are tiny in comparison to your standard honey bee. They range from 3–10mm in length, some the size of a fingernail, some so small you might think they were ants or tiny flies. Sweat bees are known in the bee world for exhibiting a metallic, shiny and vibrant lime green colour. However, they come in all sorts of colours and mixed patterns — some are fully green, others mix a green head with a yellow and black body. The bees bodies are covered with thousands of tiny bristle hairs. On some bees these hairs are a bright blonde, making them look fuzzy and soft.

Sweat bees are scientifically named Halictidae, a family of bees that occur all over the world. Over 4,000 species have been identified worldwide, 1,000 of those are in the western hemisphere. They are often attracted to the salts created during perspiration in humans, giving their nickname of “sweat bee.”

I’ve spent a lot of time in the outdoors. Sometimes it can be difficult to know where to find bees, especially early in the morning before the sun is strong enough to warm them up for flying, or in the early evening when they’re settling in for the night. But it’s easy to stumble onto their nests, if you know where to find them. Often I spend my time looking for tiny holes clustered together in a clump of soil, or clusters of holes in the trunk of a tree. Then just keep an eye out for tiny yellow faces.

Most sweat bees nest in wood structures with small holes, underneath the bark of trees, or in ground structures. They’ll find abandoned holes from other insects like beetles, or old woodpecker holes, or even in holes in the ground abandoned by ants or formed through natural erosion processes. These holes can be tiny, smaller than a fingernail! The bees lay their eggs in these holes, where they also deposit a ball of pollen to feed their young. This ball of pollen is made up of pollen from many different plants, mixed with nectar. The eggs hatch, young larvae feed on the pollen, develop into pupae, and over winter in their holes to emerge the following spring.

Some sweat bees nest nearby to one another, though they don’t share resources. This habit of nesting in the same location takes advantage of a good ground site or tree of woodpecker holes, providing safety for many offspring.

What kind of family structures do sweat bees have? Do they live alone, or in groups? Surprisingly, the answer is both.

Some sweat bees are solitary, like many other native bees, meaning every female is virile and females are responsible for building the nest and providing all pollen needed for their offspring. Solitary bees live solitary lives — the females lay the eggs, provide the pollen, and die before eggs hatch.

Some sweat bees are social, meaning they operate more like honey bees — the queen bee laying eggs, and all other bees acting as workers collecting pollen and nectar and tending to offspring. It’s a lot like a big, kind cult — everyone does their part in raising the offspring as a community.

Sweat bees are actually important pollinators, despite their tiny size. One species, the alkali bee, is an important pollinator for alfalfa, a pasture crop that requires pollination. Alkali bees nest in soils with high salt saturation, or alkaline soils, giving them their unique name. Alkali bees use a special method for popping open alfalfa flowers by applying pressure on the base of the flower. These bees are amazing pollinators of many other crops, but alfalfa growers absolutely adore them for their skills.

You can cultivate a tiny (or enormous!) bee population for an alfalfa farm without much effort. Farmers routinely create special bee beds, large plots of soil with high salt content, to attract the bees to their farms. Thousands upon thousands of bees nest in these beds, happily collecting and distributing pollen across the fields and raising their offspring.

When you’re walking through the woods, you see all the colours you would normally associate with nature. Greens, blues, many variations of browns. You might see bright reds, oranges, and yellows if you’re taking a walk in the fall leaves in many parts of the world. Everything that is a part of our ecosystem makes up a beautiful kaleidoscope of colours. The world of pollinators is no exception. Humans have spent centuries trying to recreate these colours in paintings and photographs, but bees already have those colours perfected.

Sweat bees can be a bright metallic green, reflective in the light, like no other creature on the landscape. Some sweat bees are absolutely covered in bright blonde hairs and special clear metallic wings. Others are extremely black, their body hair difficult to see. Sweat bees tend to hover over flowers, leading them to commonly be confused for flies.

Many sweat bees have stark blonde stripes on their black bodies, resembling miniature wasps. Others have red bodies, blending into reddish flowers and leaves entirely.

The gorgeous variety of colours found in sweat bees make them one of my favourite type of bee — but it helps that they’re also a wonderful addition to the diversity of our environment.

I’ve never been stung by a sweat bee, but I see them all the time. Sometimes I catch a glimpse of a bright green blur, flying past my face — sometimes I find them nestled in the depths of flowers, rolling their bodies around to collect pollen and sipping nectar with their proboscis (a bee’s  tongue), resembling a flower’s stamens because of all of the bright yellow pollen on their bristled hairs.

As a bee researcher, I commonly catch bees for pinning on a board later in the lab. These pinned insects allow us to identify the diversity of bees living in a region, and give us a glimpse into their body morphology up close (don’t worry, we gently kill them before pinning to avoid causing unnecessary harm!). I have pinned bumble bees, honey bees, and other solitary bees — but never a sweat bee. They always escape my grasp, their tiny wings moving faster than my eyes can follow, zipping away before I can secure them in a tube or vial.

Luckily, all these bees want from you is a little bit of salt from your sweat. So before you slam a hand down on that tickle on your arm, take a look. If it’s a tiny metallic green creature, be patient — give them a taste, and they’ll fly away happily.