Small piles of white powder on floorboards

[brightbluesky]

Came back from holiday to find several small piles of whitish powder on the wooden floorboards in corner of kitchen.
(I can't post photo as don't know how to).
I wiped them away and within a week they are back.
These are distinct piles of dust, NOT fine layer of dust and definitely not rust red.
I have had a preservation company guy round who prodded the floorboards and skirting with a damp meter and said there's no evidence of dampness.
The distinct piles of dust are only in this corner on about four floorboards and there is no musty or bad smell.
Any thoughts please.....

 

[DaveHerns]

Photos please. Woodworm? Any bore holes?

 

[brightbluesky]

Yes Dave, I've just been and looked and there are many tiny bore holes and equally many piles of powder.
I only cleaned the powder away last week and there's loads more!!!!!
Is this the time of year they come through the wood??
What shall I do next?

 

[jeds]

You had a preservation company round and they didn't recognise worm hole dust? Yes it's time of year for the worms to emerge.

 

[tomfe]

Wood worm like damp wood so this may indicate a problem.