Locust Borer Beetle - Megacyllene robiniae
Order Coleoptera -- beetles, besouro, coléoptères / Suborder Polyphaga / Infraorder Cucujiformia
Superfamily Chrysomeloidea / Family Cerambycidae -- capricornes, cérambycidés, long-horned beetles, longicornes
Subfamily Cerambycinae / Tribe Clytini / Genus Megacyllene / Species Megacyllene robiniae (Forster, 1771)
Live adult beetle photographed at Winfield, Illinois, USA. Shown with Goldenrod (Solidago sp.)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Locust Borer showing "longhorn" antennae

The locust borer beetle is native to North America. It attacks only black locust trees of the genus Robinia, which originally grew only in the Allegheny and Ozark mountain regions. Due to its ability to thrive in poor soils, the black locust has been widely used as a shade tree and in reclaiming land damaged by farming and strip mining. The locust borer beetle has extended its range as a result. It is now found over most of the U.S. and southern Canada. This is one magnificent insect - about 3/4" long, stately and impressive. I'd never seen one before I stumbled across this guy. The whole time I was shooting, I was saying, "What the hell is this thing!? What a COOL bug!" (Yes, I frequently talk to myself and my subjects when photographing them. People must think me crazy).

Locust borer larvae tunnel into a tree's trunk and branches, weakening the tree and making it susceptible to wind breakage. The damage from borer tunneling and wind breakage often results in deformed trees or clumps of sprout growth.
Habitiat and Life Cycle: The brightly colored adults appear when goldenrod (Solidago sp.) is in bloom, generally mid-August through September here in the midwest. I took photos of this specimen feeding on goldenrod pollen in the midst of a large mown field, hundreds of yards from trees of any variety, and so it's obvious to me the beetles will range far from their host plants in search of food. Females start laying eggs in the early afternoon and continue until dusk, August - October. Eggs are laid under the bark, around pruning wounds and wind breakage and in cracks in the bark - rarely where they can be easily detected. About a week later, the eggs hatch and small white larvae bore into the inner bark, where they make a small hibernation cell and overwinter. In the spring, the larvae bore into the woody part of the tree, eventually enlarging their tunnels until they are 3-4 inches long and 1/4 inch in diameter. By mid-July, most of the larvae begin the pupal stage, which lasts about 2 weeks. The mature adult beetles emerge through the holes made by the larvae.


This beetle is fully 1 inch long (2.5cm)