Resin bees are native bees of the Megachilidae family, which is one of the many species of solitary bee. They are active from Spring to Fall and can be found in the Eastern North America , which means they’re probably in your backyard if you’re on the East Coast. This species of bee has a ‘generalist’ diet, which means they pollinate a wide variety of flowers (having a ‘specialist’ bees focus on one or a few flower species). Resin bees primarily obtain their food from flowers. These resin collectors are similar to the Leafcutter Bee in appearance and in that they dwell in nests, rather than hives.
Resin bees are mason bees, which means they build nests using materials they find in their environment. As their name suggests, they collect resin from tree bark, leaf buds and stems, which is a sticky substance they readily collect to use in their nests or hives. They must collect resin during warm months, when it is pliable; during cold months the substance is nearly impenetrable. While honeybees and resin bees are not the same, but they do exhibit similar traits - namely, honey bees also collect resin. Honeybees distribute resin amongst their colony, where the bees then work the resin into a substance called propolis. Resin provides a multitude of benefits to resin bees and honeybees including:
Resin provides architectural benefits to nests and hives. It serves as a barrier, waterproofing and smoothing agent for the exterior and interior of the homes of each species of bee.
Resin serves as a vital antibacterial agent to protect developing larvae from disease. Both resin bees and honey bees coat their nests with layers of the substance because of its protective disease-fighting qualities to keep the entire nest/hive healthy.
Resin provides a barrier of protection from predators.
Like honeybees, resin bees build their nests with separate cells for each of their eggs. As solitary bees, resin bees leave their young to hatch, feed and cocoon on their own - referred to as “mass provisioning.” Honey bees do the opposite during child-rearing, feeding their larvae continually until they spin into a cocoon - referred to as “progressive feeding.”
Photo above by Frank Vassen.
Take a look at the photo of nesting tunnels below -- the 4th and lowest nesting tunnel contains resin bees. The life stage is actually the pupal stage. This is the way it overwinters. In the summer months each pupa grows into an adult bee, and when the resin softens, adults emerge and begin the cycle over again. When you find these occupants in your nests, leave them the way they are in the nesting tunnel. These occupants are beneficial to your garden. They will pollinate your plants during the summer months. Close the nest and set it out where offspring will emerge when the temperature is right.
Photo by Mike N., Vancouver, BC
Resin Bee Lifestyle
Resin bees have been found building nests underground and in holes, upon crevices of palm tree leaves and on pine needles. As a contrast, bellflower resin bees construct their nests around ground level, in pre-existing holes, a common trait of resin bees. These bees forage pebbles, mud, and anything else they can find, then use resin as a glue to hold their nest materials together. Due to the scarcity of natural resin, the bellflower resin bee was one of the first documented of the species to be seen adapting to urbanization - substituting synthetic materials, such as builders caulk, when making their nests. Unfortunately, the chemicals found in caulk are unhealthy for bees.
Similarities: Resin bees and Honey bees
Honeybees are oval-shaped creatures, measuring at about 15 mm long, whereas resin bees range in size between 7-27 mm in length, with a cylindrical body shape.
Resin bees have a black head and abdomen, the thorax is covered with dense yellowish-brown hairs, wings are dark but transparent. Honeybees are golden yellow with brown bands around their bodies.
Resin bees live alone in holes or crevices. Honeybees live in communities, each with its own hive. Hives are typically built in hollow trees, or along crevices.
Do they sting?
Resin bees are not known to sting unless threatened - the same goes for honeybees, which only sting as a self defense mechanism.
We know honeybees are notorious honey-producing heroes - however, resin bees do not produce honey.
Photo above by Frank Vassen.
Spotlight: Northern-Rotund “Giant” Resin Bees
Northern-rotund resin bees are indeed little giants, as their namesake: sized at between 14-24mm in length - larger than most bees in North America, characterized by long, cylindrical, ridged, shiny, hairless abdomens. Males are smaller, 2/3 the size of the females, distinguished by a bright yellow “mustache” just above their mandibles. If you get a closer look, their wings form a “V” shape on their backs. There’s a chance you might confuse the northern-rotund species for a carpenter bee, a mining bee or a European hornet. The northern-rotund resin bee is a fairly new species of resin bee in North America, only recently introduced to the U.S. in 1994 from Asia. Northern-rotund resin bees have a tendency to nest in pre-existing holes or tunnels, particularly inside of wood cavities. This resin bee species has a bad reputation due to their opportunist, invasive nature. Notably, researchers have observed giant resin bees to be an aggressive species; attacking carpenter bees, using resin to immobilize them, in order to steal their nest sites. Resin bees do not have the ability to chew into wood cavities as carpenter bees do, so they kill a carpenter builder after it has done the manual labor. The implications of such aggression from the northern-rotund bees is troubling as it poses a threat to important native pollinators, such as the carpenter bee, especially for competing interests in nesting habitats. Northern-rotund bees are also known to damage local flora while collecting pollen, leaving the flower unusable for other bees to pollinate.
The largest of the Megachile species and deemed the “largest bee in the world” is the elusive Megachile Pluto (aka: Wallace’s giant bee), an extremely rare solitary bee found dwelling in aerial termite mounds on the 3 islands of Indonesia. These giants can grow up to an inch and a half long, with a wingspan of 2.5 inches. Aside from the giants, other resin bees typically keep to themselves and are not likely to sting unless provoked.
It’s likely that resin bees are your neighbors. You can help be a hospitable neighbor by planting and maintaining healthy outdoor plants to support the resin supply for these resin connoisseurs. Better yet, get crafty - you can build a small “bee hotel” using a drilled block of timber or bamboo cane. Maintaining a clean bee hotel is key, as it can become a breeding space for parasites. Additionally, it’s important that this species has a natural supply of resin to prevent them from resorting to unhealthy synthetic substitutes. Planting native plants will promote a healthy habitat for these big buzzers.
Resin-producing plants include:
These flowering plants also yield resin:
Tarweeds and more
Check out our How to Save the Bees page for more simple ways to promote the welfare of our planet by supporting vital native species.