Another Missouri Invasive Species

Megachile sculpturalis at Springfield Botanical Gardens - Chris Barnhart

An unwelcome visitor was seen visiting the flowers at the Springfield Botanical Gardens this week, and for a change it wasn't a "Canada" goose. Chris Barnhart sent this picture of giant resin bees, Megachile sculpturalis, an Asian species probably accidentally introduced with some commercial product before first being discovered in 1994.

"The giant resin bee (Megachile sculpturalis) is so named because it is larger than most other leafcutter bees, ranging in size from 14 to 24 mm long, and because it uses its strong jaws to collect plant resin to seal the cells in which it lays eggs. This bee is native to Asia, but was inadvertently transported to the United States in the 1990's, where it was first identified in North Carolina in 1994. It is now present in most of the southeastern United States. This bee resembles bumble (Bombus spp.) and carpenter (Xylocopa spp.) bees, except that it lacks both the hairy abdomen that is present on bumble bees and the shiny abdomen that is present on carpenter bees."   EOL.org

By my definition, M. Sculpturalis is an exotic species that hasn't earned the title of "invasive species" yet, although that is somewhat a matter of taste.  I would define invasive species as exotic plants or animals that are creating damage and economic costs to society.  Researchers have reported seeing it aggressively evict native eastern carpenter bees from their nests. The frequency of these episodes and their effects on the ecosystem is not known.

From  iNaturalist.org

Although it resembles a carpenter bee, its strong jaws are not capable of boring into wood so it nests in cracks of wood walls and in holes created by carpenter bees or other wood boring creatures.  It is too early in their North American career to know if they will affect the carpenter bee population by competing for nesting sites (bad?).  These carpenter species are not on most homeowners list of favorite insects although they are important pollinators.

The female M. sculpturalis constructs its nest in a preexisting cavity by bringing in mud and rotten wood particles that are then glued together with sap and resin from trees.  Next she collects pollen on her hairy thorax (good!) and places an egg on it before sealing the cell and starting again.  The offspring live on the pollen over winter, pupate and then emerge in the spring.

Several bees may nest around a house which can be threatening but they are no danger.  The males have no stinger and the females will only sting if you hold them in your fist.  This is not a good idea with any bee and anyone trying it probably has earned a sting.