The link between honey bees and resin bees
A honey bee is not a resin bee, at least not by definition. But if you compare the behavior of honey bees and resin bees, you will find uncanny similarities.
I was a beekeeper for many years before I began to understand bees. Insight finally came, but not from studying honey bees. Only when I began to contrast honey bees with the rest of them did the bee world begin to make sense. Resin collection is a perfect example of cross-species behavior.
Honey bees are the outliers
Honey bees are outliers in the bee world, unique in many ways. But they are also surprisingly similar to other species, sharing any adaptation that proved useful through the ages.
Remember that Apis mellifera is just one species of about 20,000 named species and perhaps another 20,000 unnamed ones. Scientists have to guess at the total number because many species are tiny with small ranges. And sadly, many are endangered or have already gone extinct, even before we’ve had a chance to name them.
Resin bees are a type of mason bee
Resin bees are a large group of solitary bees belonging to the Megachilidae family. Technically, resin bees are mason bees, and like other mason bees, they build structures with materials they find in their environment. You may be familiar with mason bees that collect mud or tiny pebbles, but resin bees collect—you guessed it—resin. The resin they use is exuded from the stems, buds, and bark of various plants, especially the conifers.
Unlike sap, which is mostly water, plant resins are insoluble in water, often with a glossy appearance. Resins are often sticky, flammable, and may be brightly colored in shades of red, yellow, and brown. They contain a variety of complex organic compounds which are useful to bees.
Resin bees collect a ball of exudate in their mandibles and carry it home to their nests. Like other bees in the Megachilidae family, these bees nest in the long and narrow cavities of hollow reeds, insect burrows, or even soda straws. The resin is used to line the nest cavity and to build partitions between consecutive egg chambers or cells.
Laissez faire child rearing
After she has lined the nesting cavity with resin, the female places a ball of pollen mixed with nectar in the far end, lays an egg on top of the ball, and then builds a partition of resin. She repeats the process over and over until the entire cavity is filled, one egg to a cell. The concept of “one egg to a cell” should be familiar to any beekeeper because honey bees, too, build a separate cell for every egg.
Like most other solitary bees, once the female seals a cell, she is finished rearing that particular offspring. Eventually, the egg will transform into a small larva. This larva will eat the ball of pollen and nectar until it is gone. Then it will defecate, spin a cocoon, and pupate. This type of feeding—“Here’s the food, kid. Now you’re on your own,”—is called “mass provisioning,” meaning the provisions are supplied en masse. One and done. The kind of feeding that honey bees do is called “progressive” feeding, because the larvae are fed continually until they spin a cocoon.
The benefits of resin
The resin from plants provides several benefits to these bees. It provides waterproofing for both the interior of the nest cavity and the entrance, and many of the chemicals in resin have antibacterial properties that help to prevent disease in the developing larvae. This, too, should sound familiar to any beekeeper, because honey bees also collect resin.
Although we don’t think of honey bees as resin bees, the collection of plant resins is vital to the health of a honey bee colony. Honey bees collect resins from similar sources: bark, buds, and stems. The honey bees stuff these resins into their pollen baskets and carry them back to the hive. Inside the hive, the resins are kneaded with their mandibles and mixed with bee saliva and beeswax. Once the material becomes soft and malleable, the workers smear it on rough surfaces, cracks, holes, or any place where they want a smooth, waterproof, or antimicrobial surface. Resin processed by honey bees is known as propolis.
Plant exudates are vital to bee health
Feral honey bee cavities are often surrounded with rings of propolis to help deter pathogens, just as the entrance holes of resin bee nests are coated with a glistening layer. Plants produce these resins to keep themselves healthy. When a plant is injured, the resins ooze out of the wound, and the sticky consistency along with the antimicrobial components allow the plant to heal. By borrowing some of this sticky goo, the bees add layers of protection to their homes. Although it’s easy to remember that bees depend on plants for nectar and pollen, we sometimes forget they also raid the plant medicine chest.
If you mention propolis to a beekeeper, you can expect a groan. It’s messy, stains your clothes, cements bee boxes together, and won’t come off your hands. It destroys the look of comb honey and must be scraped, cracked, or otherwise dealt with. Unfortunately, early bee breeders spent a long time selecting for bees that collected little propolis. They believed beekeeping would be much easier if they could breed a bee that didn’t collect the stuff. But modern researchers are finding that propolis is vital to colony health no matter how inconvenient it may seem to the beekeeper.
In a recent article entitiled, “Darwinian Beekeeping: An Evolutionary Approach to Apiculture” (American Bee Journal, March 2017), Thomas Seeley suggests that beekeepers build bee boxes of rough-sawn lumber because the irregular interior surface will encourage propolis deposition. These deposits, Seeley says, will enhance the health of the colony by providing “antimicrobial envelopes.” Other researchers, too, are beginning to re-assess the role of propolis in honey bee health.
Resin bees become confused by the modern world
Normally you don’t hear much about resin bees, but one species made the news back in 2013. Megachile campanulae, more frequently called the bellflower resin bee, lives in the northeastern US and parts of Canada. Researchers discovered that some urban populations of these bees were collecting man-made materials, such as builders’ caulk, to use in place of resin. This is believed to be adaptive behavior compelled by urbanization: when the proper plant materials become scarce, the bees find alternatives. Unfortunately, the chemical polymers in caulk are not good for bees.
Although I have not heard of it, I wouldn’t be surprised to find honey bees collecting similar materials. Since we know honey bees collect sawdust and coffee grounds when pollen is scarce, it doesn’t seem far fetched that they might look for resin substitutes as well.
Glued together through time
As you can see, resin is a common feature in the bee world. To me, the existence of resin collection in multiple species is a strong indicator of its evolutionary value. We should pay attention. Far from being a mere annoyance, resin may be a beekeeper’s best friend.
Honey Bee Suite