Lyctid or Powderpost beetle:
Introduction
Lyctids are commonly known as (true) powderpost beetles because their
larvae produce a very fine, powderlike frass in their galleries (vs. bostrichids/false
powderpost beetles and anobiids, whose larvae produce coarser frass which
also contains fine wood fragments or pellets respectively). They are worldwide
in distribution, with about 11 species occurring in the United States.
Biology
Female Iyctids lay their eggs (15-50) in exposed wood pores, cracks,
or crevices. Eggs are never deposited in/on waxed, polished, painted, or
varnished surfaces. The larvae tunnel only in the sapwood and usually tunnel
with the wood grain. As they bore, the larvae loosely pack their tunnels
with very fine powderlike dust (like talcum powder or flour). After several
molts requiring 2-9 months, the mature larva bores to near the surface
and constructs a pupal chamber and pupates.
When the adult emerges, it bores straight to the wood's surface and
exits/emerges. Indoors, adults usually emerge in late winter or early spring
and with little feeding, mate. Under very favorable conditions, developmental
time (egg to adult) usually requires 9-12 months, but may be as short as
3-4 months or as long as 2.5-4 or more years.
Although some Iyctids are strong fliers, most tend to lay eggs in
the wood from which they emerged. Since Iyctid larvae cannot digest cellulose,
they feed only on the cell contents which is primarily starch, but also
sugar and protein.
Habits
Lyctids attack the sapwood and only that of hardwoods, usually less
than 10 years old. They attack both lumber and manufactured products; they
also attack structural timbers but hardwoods are rarely used for this purpose
today because of their cost. The wood moisture content required for beetle
development is 8-32%, with greatest activity at 10-20%. Adults are
active at night, readily fly, and are attracted to light.
Lyctids are usually brought into structures in wood which contains
their eggs and/or larvae. This wood is typically infested during drying
time or storage. Finish on wood prevents egg laying.
They usually attack oak, hickory, and ash, but will attack other
native and tropical hardwoods. Lyctids often attack bamboo.
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Mark Pierce
Oregon Certified Home Inspector
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Cell:503-757-7784
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