Bostrichid Beetles

Order/Family: Coleoptera/Bostrichidae

Scientific Name: Various

Description: The bostrichid beetles range from 1/16- to 1-inch in length. They have an enlarged prothorax (first body segment) which gives them a humpbacked appearance. The body is elongate and cylindrical. The head usually points straight down and is hidden from view by the large prothorax. Most bostrichids have a roughened thorax, anf their short antennae usually end in three or four enlarged segments.

The black polycaon, Polycaon stoutii, is unlike the majority of the bostrichids. It is 1/4- to 7/8-inch long, coal-black with a prominent head that points straight out from the thorax, and has an oval prothorax with rasp-like teeth. The wing covers have small holes.

The lead cable borer, Scobicia declivis, is a more typical bostrichid. It is 1/4-inch long, cylindrical, brown, black, or red-brown beetle with red mouthparts, legs, and antennae. The last three segments of the eight-segmented antennae are greatly enlarged. The head is concealed by the hood-like prothorax which has many puncture-like holes in the front half. The wing covers have deep punctures arranged in rows.

Biology: The bostrichid female differs from anobiid and lyctid beetles because they bore into wood to form an egg gallery where the eggs are inserted into pores in the wood as she moves in and out of the egg tunnel. The eggs hatch in about three weeks, and the larvae feed on the wood for the next nine months. The pupal stage lasts two weeks; however, the new adults stay in the tunnel for four to six weeks, then chew their way out of the gallery, emerging through a round exit hole 1/8- to 1/4-inch in diameter. The developmental time (egg to adult) requires approximately one year.

Habits: The bostrichids attack seasoning or newly-seasoned sapwood of hardwoods less than ten years old. They occasionally attack softwoods. The black polycaon is found primarily in the far Southwest and Pacific coast states and attacks hardwoods and plywood. The leadcable borer is common along the pacific Coast and bores through lead cable coverings, plastic pipes, etc. Bostrichids infest the prunings from fruit trees and ornamentals. Bostrichids rarely re-infest. The larvae bore parallel to the grain, filling the tunnels with tightly packed meal-like frass which tends to stick together.

Control: The first indications of bostrichids within a structure is usually the emergence holes formed by the adults when they leave the larval galleries and frass which accumulates beneath the infested material. Infested wood can be removed and replaced with treated wood.

Copyright © 2001 [Alan Luke]. All rights reserved.
Revised: 06/25/10. Home