Giant Resin Bees

Side view of giant resin bee with pollen covering the hairs on its body
Giant Resin Bee Classification
Class: Insecta
Order: Hymenoptera
Family: Megachilidae
Genus: Megachile
Species: M. sculpturalis

The giant resin bee, Megachile sculpturalis, is a species of leaf-cutting bee native to Asia.[1] Giant resin bees are also known as sculptured resin bees. These bees belong to the genus Megachile.

Giant resin bees are known to be larger than many other members of this genus, including US-native leaf-cutter bees. The name giant resin bee refers to the bee’s large size, as well as the fact that it utilizes the sticky resin extracted from trees [2].

The giant resin bee is known to use this resin in building its nests, and some have even been observed using it to kill carpenter bees.

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    Where Can Giant Resin Bees Be Found?

    Giant resin bees can be found in East Asia, in Japan and China. The giant resin bee was introduced to America in the early 1900s, with the first confirmed sightings occurring in North Carolina.

    It is widely believed that giant resin bees were first introduced to the USA through international trade.

    The giant resin bee has now spread throughout the United States, being found in most states east of the Mississippi River. As giant resin bees prefer temperate, subtropical, and humid climates, it is anticipated that their range will continue to expand throughout the continental United States.

    Why Are They Called Giant Resin Bees?

    Giant resin bees are named so because of their reliance on sticky resin to construct nests and fight other bees. 

    The “giant” aspect of giant resin bees is due to their massive size when compared to other bees, even when compared to other members of the Megachile genus.

    How Big Are Giant Resin Bees?

    Giant resin bee males typically measure 19 to 22 millimeters in length, while females typically measure 21 to 25 millimeters.

    Generally, female giant resin bees are larger than their male counterparts. The size of giant resin bees is a reliable indicator of their distinction from other bees with similar appearances, such as carpenter bees.

    How to Identify a Giant Resin Bee

    When identifying a giant resin bee out in the wild, observers are likely to notice its size as the first characteristic to identify it. These bees are very large, particularly the female giant resin bees. [4]

    It is pertinent to note, however, that giant resin bees have very narrow and elongated bodies. However, giant resin bees remain much larger than other types of bees in the United States. There are ridges on the abdomen of giant resin bees that allow observers to distinguish them from similarly-looking bees.

    As a result of the numerous hairs that cover the giant resin bee, particularly on its abdomen, the bee is able to collect pollen from a wide variety of plants. This pollination method differs from many other species of bee.

    You can differentiate male giant resin bees from females by looking at their faces. There is an interesting yellow marking on the lower face of male giant resin bees.

    Some individuals may perceive this marking as a moustache. Female giant resin bees lack this marking, so it is a reliable way to tell the two sexes apart, especially if their sizes cannot be compared directly.

    Male giant resin bees have a blunt abdomen compared to the pointed abdomen of female giant resin bees. Both sexes of giant resin bees exhibit the typical black and yellow-brown coloring people associate with bees.

    A giant resin bee can also be identified by its dark, black, and brown wings with darker markings at the edges.

    Where Do Giant Resin Bees Live?

    Known as solitary bees, giant resin bees live alone in holes in trees, caring for their eggs and larvae alone. If given the opportunity, female giant resin bees will nest in any type of hole in a tree.

    However, even though they possess strong mandibles they do not possess the ability to construct these holes for themselves[5].

    Because female giant resin bees are unable to excavate with their mandibles or other appendages, they will search for any naturally occurring cavity. Additionally, female giant resin bees will search for cavities that were previously used as nesting sites by insects of a similar species.

    In many cases, giant resin bees construct nests out of bore holes left behind by creatures such as beetle larvae or excavating bees.

    The female giant resin bee will begin constructing its nest after finding the appropriate size cavity. They accomplish this by laying their eggs and providing them with nectar and pollen.

    The eggs of giant resin bees are placed in cells made of sticky resin gathered from trees. Additionally, giant resin bees use this resin to create cell walls that separate their eggs.

    Giant resin bees find this resin to be extremely useful, as the females will also use it to seal and waterproof their newly constructed nest entrance after they have finished constructing the cavity.

    Tree resin used by giant resin bees seeping out of a tree
    As their name suggests, tree resin plays an instrumental role in the life cycle of giant resin bees. In addition to creating nests, resin is also used as a weapon against other bees.

    It has been reported by some researchers that giant resin bees kill carpenter bees before taking their excavated homes for themselves. With the help of sticky resin, giant resin bees are capable of immobilizing and killing these carpenter bees.

    In addition to providing suitable nesting sites for these giant resin bees, this practice can also serve to reduce the number of carpenter bees in a particular area. 

    There is concern among some researchers that the giant resin bee species may in time adversely affect the carpenter bee in the United States.

    According to other researchers, giant resin bees have attacked other species of bees, including honey bees. It is unclear, however, whether this behavior is common or unusual.

    A giant resin bee is also known to nest in man-made “bee hotels.” These structures are built to provide nesting areas for solitary bees, and giant resin bees make use of any bee hotels within their range.

    How Big Is a Giant Resin Bee Colony?

    Close up shot of a giant resin bee resting on a stick

    Giant resin bees do not form colonies. However, some females have been observed to build their nests close to other female giant resin bees. Therefore, it is not surprising to find a large number of giant resin bee nests in one particular location, even though they do not form a colony.

    A female giant resin bee may have up to 10 larvae in its nest, therefore some areas may have a large number of giant resin bees.

    What Do Giant Resin Bees Eat?

    Resin bee cutting and removing a piece of leaf to build its nest
    Resin bees are often spotted cutting sections off leaves. Don't mistake this for them eating the leaves, instead they use leaf cuttings to build their nests.

    The giant resin bee is known for collecting and eating pollen and nectar from an extensive variety of plants. The giant resin bee is known to feed on nectar and pollen from at least 43 different types of plants in the United States alone.

    Due to their origins in Eastern Asia, giant resin bees appear to prefer plants indigenous to this region. One of these plants is kudzu, an invasive species from Eastern Asia. There is a vine known as kudzu that is common throughout the southeastern United States, which is where most giant resin bees reside.

    It has also been observed that giant resin bees leave small puncture marks on certain types of plants. Everlasting peas and Japanese pagodas are among these plants. They are generally located on the petals of both of these plants and are very small.

    Some researchers have noted that, although giant resin bees do not appear to cause long-term damage to flowers, they can cause plants to be unable to be pollinated by other insects in the future.

    These markings, however, allow scientists and researchers to track and investigate the types of plants giant resin bees visit for food, which can be extremely valuable in the study of this species.

    Do Giant Resin Bees Pollinate?

    The giant resin bee pollinates plants by collecting pollen from plants on its hairy abdomen. The pollen is then returned to the giant resin bee nests, where it is used as food for the larvae and eggs.

    Pollination by giant resin bees differs slightly from that of other bee species.

    Through the use of hairs on their abdomen, giant resin bees are able to collect pollen from a wide variety of plants throughout the United States. The pollination method of giant resin bees differs from the pollination method of many other species of bee. These bees use hairs on their back legs in order to collect pollen.

    Despite their ability to pollinate a wide variety of plants, giant resin bees are known to prefer plant species that are native to Eastern Asia, such as kudzu vines.

    Do Giant Resin Bees Make Honey?

    Giant resin bee collecting pollen and nectar from a flower

    Giant resin bees do not produce honey. As with most bee species, with the exception of honeybees and a few others, giant resin bees are unable to produce honey. However, giant resin bees contribute significantly to the ecosystem through pollination.

    While giant resin bees remain an invasive species that has the potential to negatively impact native bee species throughout the United States, they are critical pollinators.

    The impact of giant resin bees on other species is considerable, although, in general, the entire species of giant resin bees in the United States have no significant environmental impact.

    Do Giant Resin Bees Sting?

    While male giant resin bees are not able to sting, females may do so if provoked. However, giant resin bees are not known to be particularly aggressive towards humans unless they are threatened. If someone encounters a giant resin bee in the wild, it’s likely to fly away from them.

    How to Get Rid of Giant Resin Bees

    Contacting a local beekeeper is the most effective method of removing giant resin bees. Despite the fact that giant resin bees are not inherently aggressive, females may sting humans if they feel threatened.

    Giant resin bees are known to make their nests in bee hotels or Mason bee houses. It is possible to prevent the spread of giant resin bees by not having these man-made habitats around a property.

    It is pertinent to bear in mind, however, that removing these structures may limit the ability of desirable bees to establish their nests. It may be an effective strategy for people to periodically inspect these structures to ensure that giant resin bees are not taking over.

    Closeup shot of a giant resin bee

    Another method of eliminating giant resin bees is to prevent them from creating nests in the first place. You can accomplish this by painting over the wood in your area. This will prevent other species from boring holes into it, which the giant resin bees will eventually occupy.

    If giant resin bees have already built nests in an area where they need to be removed, it is recommended that the nests be destroyed. As a result, the giant resin bees will move on to seek out a new nest.

    Reproduction & Lifecycle of Giant Resin Bees

    The male giant resin bee dies very soon after mating, leaving the female to lay and care for the eggs.

    A female giant resin bee collects enough pollen and nectar to fill one brood cell before laying an egg on top of it. These cells are normally formed during the summer months. The nests of giant resin bee females may contain up to ten egg cells.

    As giant resin bee larvae continue to grow throughout the winter, they will feed on the pollen and nectar mixture. A new generation will emerge from their cells in the summer and continue the process of reproduction. 


    [1] entnemdept [2] [3] bdj [4] arboretum [5] Capital Naturalist 

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