On Tue, 19 Jun 2012 19:38:53 +0100, Janet wrote:

The heart tunnels could be insects and the larger holes made by
woodpeckers trying to get to the insects. I've seen huge splintered
holes made through wooden birdboxes, by woodpeckers determined to get
to the inhabitants.

That would be my guess as well insect exit holes are not normally
great messy things like that. A google image search on longhorn
beetle exit shows round holes about 1cm across.

There doesn't seem much about for the Goat Moth apart from a fully
grown larva being 10cm long so I should imagine well worth a
woodpecker putting in a fair bit of effort to get at one. Any wood
chips/splinters on the ground below the holes? An emerging insect or
grub wouldn't make wood chips/splinters. With Goat Moth there would
be the poo from the larve falling out of holes as well, just as you
describe.

Isn't google wonderful. B-)

--
Cheers
Dave.