BORING LIFE
143
deep, and are not lined with shell; Although the burrows
are
appareny made in the same manner as Teredo, by
means of the shell, there are no pallèts and-the animals
cannot digest the wood.
The same is true of the third
type of Molluscan borer,
This is a native of
the tropics and is very likea small mus$el in appearance ; »
_
its burrows are not generally more than two' and a half
inches long and one inch wide, ie, the size of the animal
which lives within
Neither of these animals has
attained the efciency of Tereddas a borer and both seem
to seek the Woodmainly as a means of protection, and
not also as a source of food as does the Shipworm.
‘
There are a number of Crustaceans which habituallÿ
bore into wood.
One of these stands ont pre—eminent, like
the Shipworm amorigst the Molluscan borers,_on account
of its ubiquity and the great damage that it does.
It is
the Gribble, Limnoria lignb7um, a little creature resembling
a miniature Woodlouse, usually between one eighth and one
Sixth of an inch. long and with a semi—cylindrical body'
divided into segments (Plate 52).
It has seven pairs of
short legs each ending witha sharp, curved claw by means
of which the animal holds on to the sidesbf the burrow.
_
_
Beneath the hinder end of the body_there are ve pairs
_
of legs each carrying two broad plates which act as gills, .
these keep up a continuous movement during the life of
the animal and so constantly renew the Water needed for
respiration.
The animal bores into the wood by means of
a pair of stout “ mandibles,” one on either
side 'Ofthe mouth.
These are not identical, for the one On the right has a sharp
point and a roughened edge_Which ts into a grbove with
'
& rasp-like surface in the left mandible, the whole pr0viding
a “ rasp—and-le
”
combination, as shown in Figure 31.
Unlike the burrows of the Shipworm, those
of the Gribble
_
are always the same width throughout, so that it appears
143
deep, and are not lined with shell; Although the burrows
are
appareny made in the same manner as Teredo, by
means of the shell, there are no pallèts and-the animals
cannot digest the wood.
The same is true of the third
type of Molluscan borer,
This is a native of
the tropics and is very likea small mus$el in appearance ; »
_
its burrows are not generally more than two' and a half
inches long and one inch wide, ie, the size of the animal
which lives within
Neither of these animals has
attained the efciency of Tereddas a borer and both seem
to seek the Woodmainly as a means of protection, and
not also as a source of food as does the Shipworm.
‘
There are a number of Crustaceans which habituallÿ
bore into wood.
One of these stands ont pre—eminent, like
the Shipworm amorigst the Molluscan borers,_on account
of its ubiquity and the great damage that it does.
It is
the Gribble, Limnoria lignb7um, a little creature resembling
a miniature Woodlouse, usually between one eighth and one
Sixth of an inch. long and with a semi—cylindrical body'
divided into segments (Plate 52).
It has seven pairs of
short legs each ending witha sharp, curved claw by means
of which the animal holds on to the sidesbf the burrow.
_
_
Beneath the hinder end of the body_there are ve pairs
_
of legs each carrying two broad plates which act as gills, .
these keep up a continuous movement during the life of
the animal and so constantly renew the Water needed for
respiration.
The animal bores into the wood by means of
a pair of stout “ mandibles,” one on either
side 'Ofthe mouth.
These are not identical, for the one On the right has a sharp
point and a roughened edge_Which ts into a grbove with
'
& rasp-like surface in the left mandible, the whole pr0viding
a “ rasp—and-le
”
combination, as shown in Figure 31.
Unlike the burrows of the Shipworm, those
of the Gribble
_
are always the same width throughout, so that it appears