Locust Borer

Photo by: Bryan Reynolds

Megacyllene robiniae

Black with yellow stripes, or yellow with black stripes? For Megacyllene robiniae, this question remains wholly unanswered. The Locust Borer is a relatively small parasitic beetle stretching to about three-quarters of an inch, but this elongated body packs an extremely conspicuous color scheme. The adults of this species are identified through their long black antennae, reddish legs, and their conspicuous patterns of yellow and black spanning the length of the body. The yellow bands take the rough shape of a “W” which further aids in identification of this beetle. The grubs of this species are less spectacularly colored, like many grubs they are observed to have a dark round head and body segments that give them a lumpy appearance. The pupae of this species look like yellow mummies, with adult features clearly visible. The unique trait of this species is that the grubs find a sole host in the Robinia pseudoacacia L., the black locust tree. As a result of this exclusive parasitic relationship, the Locust Borer finds it’s range coinciding with where its host tree andornamental cultivars are cultivated, specifically across the Eastern United States, spanning from West Virginia to the southeast corner of Oklahoma. Infection of a black locust tree begins when the adult beetle lays its eggs on the rough bark of thetree, followed by the grub eating its way into the tree. Repeated infection often causes the tree to structurally weaken, and this is exacerbated by extended droughtand poor soil which simultaneously increases Locust Borer activity.

The adults of this species are an important pollinator. Although the grubs feed on the trunk and branches of the Black Locust tree, the adults feed on plant pollen. TheLocust Borer has a preference for pollen of goldenrod, but has been known to feed on other flower pollen when goldenrod is unavailable.

As a pollinator, this species is very helpful to the native flower populations of the regions it inhabits. This beetle does not suffer extensive predation from the species native to its environment, and as a result it is often found among undeveloped fieldsfreely eating and pollinating.

Written by: Joshua Hughes, an undergraduate Aerospace Engineering student at the University of Oklahoma