A lumberjack of the night
On a July night in Pittsburgh, a large brown beetle was clinging to the wall beside a porch light, looking like it had flown in from a different century. Its antennae were long and saw-edged, its body heavy and blunt, and it sat there without moving as if the light were the only thing in the world worth attending to. Close up, its mandibles looked strong enough to split a pencil, a hint of the wood-chewing life it had left behind.
This is Orthosoma brunneum, the brown prionid, a member of the longhorn beetle family Cerambycidae in the order Coleoptera. The prionids are the lumberjacks of the longhorn world: big, broad-shouldered beetles whose larvae spend years tunneling through dead and decaying wood, grinding it down with powerful jaws. This species favors pine and other conifers, and in the forests of the eastern United States it is one of the largest beetles you are likely to meet.
The adults live for a short, bright chapter of the story. They rarely feed much, their business being to find each other and start the next generation, and they are strongly drawn to lights, which is how so many of them end up on porches in July. The serrate antennae, each segment notched like a saw blade, are a prionid trademark.
The name Orthosoma combines the Greek words for “straight” and “body,” and brunneum simply means “brown.” A straight, brown body built for a life inside wood: the name is almost a job description.
