G'day Housewright!

Not sure of you've already got the info you're after, but I thought I would add the following:

i) Powder post beetles are after the starch that lies within the cells of the sapwood...so they don't pose much risk to heartwood, and generally bugger-off after the sapwood has been chomped.

ii) There's some argument about required moisture content and humidity, but the required range is 6-32% MC and 7-40% H...doesn't really narrow it down much does it!

iii) There are two types of powder post beetle: Bostrychidae and Lyctidae (more common I think)...the adults are about twice the size of a pinhole borer or furniture beetle and half the size of a Longhorn.

iv)I was taught to identify the grubs by looking at the mess they make: they don't make frass pellets like many other wood borers, but instead leave the dust choking their caverns. This often expands and deforms the thin layer of wood that they leave at the surface of timbers; giving it a bulged look (very brittle to touch).

v) Surface treatments don't work very well for killing off an active population unless applied early days, but can prevent re-infestation.

...have a look at Brian Ridoubt's 'Timber Decay in Buildings' (Amazon carries it...I just checked)