I will start with the flatheaded borer. Flatheaded borers tend to be non-reinfesting, at least at lumber in the house, so they are not considered to be a serious worry. That does not mean they do not leave distinctive exit holes in wood, it is just that once they have left the premises, they don't come back. Damage is not chronic or ongoing. That is not true of most of the roundheaded boring beetles, which will be described in separate blogs.
The exit hole below, while enlarged (usually they are about 1/4" across) has the distinctive shape of a hole made by a flatheaded borer. All wood boring beetles lay eggs on wood, the larvae hatch and move down into the wood through a crack in the wood. There they feed for a certain length of time -- which can be many years -- then they pupate and exit, leaving their distinctive exit hole. That hole, because of the size and shape tells a pest inspector a lot about what had been living in the lumber. Take a careful look at this exit hole in a live tree. It is from a flatheaded borer.
Why is the hole oval? Well, if you are wondering about that, then we are into the crux of the proper means used to identify the insect. The oval hole is the result of the flat head. Take a look at this enlarged photo of the larvae. Note the wide, flat, head.
In the Pacific Northwest, the most common flatheaded borer is the buprestid beetle, the most common of the species being the golden buprestid. An adult golden buprestid beetle is shown below.
One thing that separates this flatheaded beetle from the roundheaded boring beetles, which are more prone to causing serious structural damage, is that the flatheaded borers tend to lay eggs in live trees. They do not target houses as good places to raise a family. Fact is, these insects never wanted to be in lumber in the first place. Now, they might end up in lumber because it was not kiln dried during the milling process, so the larvae that were inside the tree survived the transition from live tree to lumber. Flatheaded borer larvae can live in wood for many years -- some entomologists speculate that could be up to 20 years. They do not reinfest at a house because, once they pop their heads out, they want to get out of there and find a live tree to lay their eggs in. Hence, we say that the insect does not reinfest the house and we inspectors appreciate that.
I hope this is not too technical, more to come on the roundheaded borers -- anobiid, lyctid and cerambycid beetles.
Steven L. Smith
Bellingham WA Home Inspections
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