Size: |
Powderpost beetle (bostrichid) adult is 1/16-1 in (2-24
mm); one western species is 2 in (52mm) long. Most found indoors are
1/8-1/4 in (3-6 mm) long. Mature larvae are 1/4-3/8 in (5-8mm) long. |
Characteristics: |
Most species are long and cylinder shaped, with rasp-like teeth,
heads going downward, so not easy to see from above. A few species
have flat bodies, no rasp-like teeth, and heads easy to see from above;
antennal club has 3-4 segments, often enlarged to one side. Larvae
are C-shaped with enlarged thorax; legs are hairy with 4 segments. |
Color: |
Adults are reddish brown to black. Larvae are nearly white. |
Droppings: |
Powdery frass which resembles fine meal; contains fine wood fragments,
no pellets. |
Geographic Range: |
Around the world; about 60 species in the United States. |
Comparison with other species: |
Bostrichids, or false powderpost beetles, differ from lyctids,
which were first to be called powderpost beetles because of their
powdery frass. Deathwatch beetles (anobiids) have expanded club segments
on antennae, no rasp-like teeth. Powderpost beetles (lyctids) have
flat bodies, head easy to see from above, and abrupt 2-segmented clubs
on antennae. Bark and ambrosia beetles have elbowed, clubbed antennae.
Pinhole borers and ambrosia beetles have large, flat, 1-segmented
clubs on antennae, and no rasp-like teeth. |
Habitat: |
Sapwood of both hardwood and softwood lumber, and products, that
are less than 10 years old, with a moisture content of 6-30% or more. |
Food: |
Bostrichid larvae feed on wood cell contents, which is mainly starch,
with some protein and sugar. They cannot digest cellulose. |
Biology: |
Unlike anobiids and lyctids, female bostrichids bore into wood,
making tunnels across the grain of the wood before laying eggs in
wood pores. Larvae tightly pack their mealy frass into the tunnel
behind them as they bore through the wood. After molting several times,
a mature larva bores closer to the surface, makes a chamber, and pupates.
The emerging adult bores to the surface and exits. Development from
egg to adult usually takes 1 year. For some species that breed in
partially seasoned wood, it may take up to 5+ years in fast drying
wood. |
Invasion: |
Beetle adults dults are usually seen outside of wood during spring-autumn. |
Damage: |
Structural damage to lumber and manufactured products. Black polycaon
(w. U.S.) attacks hardwoods, including plywood. Leadcable borer (Pacific
Coast) bores through lead cable covering and plastic conduits. Redshouldered
shothole borer (e. U.S.) attacks hickory and persimmon. Bamboo powderpost
beetle (bamboo borer) larva feeds on stored food, spices, and drugs.
Oriental wood borer infests some hardwood imports from tropical Asia. |
Detection: |
- Look for round exit holes with diameter of about 1/8-1/4 in
(2.5-7 mm), accompanied by piles of powdery frass without pellets.
- Identify correct beetle family (and sometimes species).
- Identify on the basis of the type and age of wood, type of product
damaged, exit hole size and shape, frass, and wood moisture, since
these insects are rarely seen.
- Have professional inspection to determine activity.
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