Beetles on Goldenrod

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Last week, Erik Draper reported that Goldenrod (Solidago spp.) is in full bloom in Geauga County in northeast Ohio meaning the golden-yellow blossoms of this beautiful native plant can now be enjoyed throughout the state.  Soldier beetles (Chauliognathus pennsylvanicus, family Cantharidae) and locust borer adults (Megacyllene robiniae, family Cerambycidae) are commonly found on the flowers adding to the plant's interest to entomophiles.

 

In fact, the black and yellow locust borers feed almost exclusively on goldenrod nectar and pollen causing some entomologists to speculate that the beetle's coloration may help it to dodge predators as crawls on the color-matching flowers.   Locust borers should more appropriately be called "black locust borers" because the beetle only attacks the main stems and branches of black locust (Robinia pseudoacacia) trees including horticultural varieties and cultivars of this species.  The beetles do not attack honeylocust (Gleditsia triacanthos).  Damage to large forest trees can cause structural weakening resulting in branch and trunk breakage.

 

Locust Borer

 

Soldier may be found on a range of late-season flowers from goldenrod to flowering herbs.  The markings on their front wings (elytra) coupled with the beetle's tawny color, make them look like they're wearing a WWI-era soldier's uniform, thus the common name.  The beetles are also known as "leatherwings" based on their soft, leather-like front wings, and "goldenrod beetle" based on their fondness for the nectar and pollen of the plant.

 

Solder Beetles

 

Soldier Beetle

 

The beetle's elytra do not extend the full length of the beetle which leaves the tip of the banded abdomen exposed.  Their exposed abdomens, size, shape, and general appearance make these beetles appear as dead-ringers for fireflies in some people's eyes.  However, no amount of prodding or cajoling will cause them to flash as they lack the necessary bioluminescent equipment.  Soldier beetles cause no harm to plants since they feed on pollen and nectar.  Indeed, they are considered beneficial insects since they will also hunt down and consume caterpillars, aphids, and other soft-bodied insects that may be plant pests.  Their larvae are also carnivorous feeding on insects in the soil.