The Japanese Pagoda Tree (Styphnolobium japonicum) is an ornamental tree introduced from Asia, and best known for its showy bloom in late summer, long after the flowering period for most trees. A beautiful specimen can be found at Falls Lake, in the Blue Jay Point County Park. At peak flowering, the tree can be located by following the loud thrumming sounds of the visiting pollinators. The masses of flowers attract a variety of bees and bumblebees, which arrive in very high numbers. Their frantic activity causes a constant rain of flower petal fragments that litter the ground all around the tree like a white skirt.
The compound leaves and terminal flower panicles are beautiful and symmetrical when viewed from below.
The flowers are typical of the legume family (Fabaceae) and resemble those of the related Black Locust – Robinia pseudoacacia.
The Giant Resin Bee (Megachile sculpturalis), present in high numbers on the tree, is by far the most numerous of the pollinators. They are easy to see and identify due to their large size and cylindrical, elongated bodies. See below.
The massive mandibles present on the females are often easily seen when closely approaching the bee, and serve as an additional identifying characteristic.
The Giant Resin Bee is a member of the leafcutter bee family (Megachilidae), and the mandibles are mainly used to chew leaves and collect plant resins.
The Giant Resin Bee is an Asian species, introduced into the United States relatively recently. It was first reported here in North Carolina in 1994 and has since spread widely throughout the Southeast. It is one of the main pollinators of the Japanese Pagoda Tree in China and Japan, and since its introduction into North Carolina, it reunites with the tree once again on scattered streets and in parks. On the dark side, it also pollinates the highly invasive Kudzu and Purple Loosestrife in their native home in Asia, and in the United States. Obviously neither of these species need further help, so the impact on them is probably limited.
Giant Resin Bees visit my backyard every summer, where they completely commandeer a Mason Bee nest block. In the photo below, the shiny, silvery plant resins can be seen plugging the bottom three holes on the left. The bees form pollen into balls, place the balls into the holes in the nest, and lay their eggs on the pollen ball. They then seal the hole with the plant resins.
Giant Resin Bees are solitary, but sometimes interact when they are building a nest. They often pay little attention to each other, but they sometimes quarrel over a particular hole. In the sequence below, a female can be seen starting to pull another female out of a hole.
Below, she finally succeeds in dragging the other female out of the hole.
They face off and clash for awhile, but don’t do any real harm to each other. This sequence was repeated several times before the aggressor finally tired of the game and selected her own hole.
Giant Resin Bees are known to utilize the wooden tunnels vacated by Carpenter Bees. Recently it has been reported that the Giant Resin Bee actively displaces Carpenter Bees in some areas. One wonders if they evict Carpenter Bees in the same way as illustrated above. Entomologists consider the recent introduction of Giant Resin Bees to have had a minimal impact on the environment, but time will tell.
The Japanese Pagoda Tree pictured in this article has shown no signs of spreading from its present location, and the species in general has had minimal invasive impact in the South. However, it has become naturalized in spotty locations in the Midwest and Mid-Atlantic regions.