r46
‘
THE SEAS
;
do this by hollowing out little burrows from the side of
;
-
the parent burroW, and never by leaving the burrow and
beginning a new one in fresh timber.
As we shall see later,
the fact that fresh timber is always infected by adult and
_
,
not young Gribbles is unf0rtunate from the point of view
of the “protection of wood.
_
'
The ravages of the Gribble are always clearly apparent on,
the surface of the wood which is gradually rotted away until
'
the outer layer falls off ; the Gribble is then able to penetrate
still deeper and so, layer on layer, the wood is destroyed
_
(Plate 52).
The
Gribble is always especially abundant
in such structures as pier piles about low—water mark_and
here iteats deepest into the wood, which tapers away and
‘
nally breaks through at this point.
So numerous are
'
they in badly infected wood, that between 300 and 400
have been collected from a square inch of timber.
There is no evidence that the Gribble can actually
digest the wood though it certainly swallows large quantities
_
'
'
of the fragments which are bitten off. by its powerful
mandibles.
It has been found boring in the insulating
covering of submarine cables so that clearly it does not
depend on woodto the same extent as does the ShipWOrm_ —
which has neVer been found anywhere but in wood.
Some
.
'of the other crustacean borers'and the mollusc Xylophaga
have also been found in the insulation of cables and all
_thesecreatures: appear to bore f0‘rthe protection it aff0rds
,
'
them and 'not for the purpose of obtaining food.
‘
.
'
There are
Several Other crustacean wood borers. The
most common of these is a creature known as Chelwa
(it has no comfnon_namé, unf0rtunately) Which
is slightly larger than the Gribble, and flattened from side '
to side, being a' relative of the common sand—hoppers of
the” shore.
It
usually works along with the Gribble,
but nearer the surface of the wood, and is almost as wo'rld-
‘
THE SEAS
;
do this by hollowing out little burrows from the side of
;
-
the parent burroW, and never by leaving the burrow and
beginning a new one in fresh timber.
As we shall see later,
the fact that fresh timber is always infected by adult and
_
,
not young Gribbles is unf0rtunate from the point of view
of the “protection of wood.
_
'
The ravages of the Gribble are always clearly apparent on,
the surface of the wood which is gradually rotted away until
'
the outer layer falls off ; the Gribble is then able to penetrate
still deeper and so, layer on layer, the wood is destroyed
_
(Plate 52).
The
Gribble is always especially abundant
in such structures as pier piles about low—water mark_and
here iteats deepest into the wood, which tapers away and
‘
nally breaks through at this point.
So numerous are
'
they in badly infected wood, that between 300 and 400
have been collected from a square inch of timber.
There is no evidence that the Gribble can actually
digest the wood though it certainly swallows large quantities
_
'
'
of the fragments which are bitten off. by its powerful
mandibles.
It has been found boring in the insulating
covering of submarine cables so that clearly it does not
depend on woodto the same extent as does the ShipWOrm_ —
which has neVer been found anywhere but in wood.
Some
.
'of the other crustacean borers'and the mollusc Xylophaga
have also been found in the insulation of cables and all
_thesecreatures: appear to bore f0‘rthe protection it aff0rds
,
'
them and 'not for the purpose of obtaining food.
‘
.
'
There are
Several Other crustacean wood borers. The
most common of these is a creature known as Chelwa
(it has no comfnon_namé, unf0rtunately) Which
is slightly larger than the Gribble, and flattened from side '
to side, being a' relative of the common sand—hoppers of
the” shore.
It
usually works along with the Gribble,
but nearer the surface of the wood, and is almost as wo'rld-