My husband was chopping down a rotten pitch pine last week and found dozens of beetles under the bark. Knowing my interest for beetles, he brought one home for me to see (and photography with my macro lens!). 

We were able to identify it as a ribbed pine borer (Rhagium inquisitor), a member of the longhorn beetle family (Cerambycidae) that is widespread throughout North America and Eurasia. The ribbed pine borer is unusual within this family, however, as it has relatively short antennae; most longhorn beetles have antennae that are at least half as long as their body, if not longer. Although variable in size, ribbed pine borers have strongly ridged elytra, which are distinctive. 

As luck would have it, a few days later we were hiking in the Bourne Town Forest and my husband pointed out a dead pitch pine with holes in the bark similar to the one he’d recently taken down. The tree was rotten enough that we were easily able to pull a few large chunks of bark away, revealing numerous ribbed pine borers underneath, each tucked into a neat little circular chamber. 

Ribbed pine borer mating occurs in May or June, after which females choose old conifer trees, particularly pines, on which to lay their eggs. They often select trees that have been infected with fungi, damaged by fire or with damaged bark. The larvae take two to three weeks to emerge and then bore through the bark into tree’s cambium, where they will develop for two years. Pupation occurs in a ring of wood fibers under the bark. Adults overwinter in these “pupal rings” or nearby under loose bark, and emerge from the wood en masse in the spring starting the cycle again.

While often considered pests, wood-consuming boring beetles play a beneficial role by recycling dead and drying trees.