478
N . BALAKRISHNAN NAIR AND M. SARASWATHY
Perhaps the most economical and effective method for checking
ravages of shipworms may be the least tried, namely biological control.
Several predators, parasites and associates of unknown relationship are
known from shipworms (vide supra) such as protozoans, planarians and
polychaetes. Some of these are known to attack and devour them piecemeal.
Despite man’s ceaseless fight against shipworms, with all available
resources and techniques, their relentless destruction continues and a
thorough re-orientation in our techniques of warfare has become
imperative. The discovery of an effective panacea depends on a better
understanding of the ecology of these specialized bivalves.
XX. TIMBERS OF UNUSUAL DITRABILITY AGAINST SHIPWORMS
No woods have been shown to be indefinitely immune to the
destructive activity of shipworms. However, certain timbers are known
t o possess a greater degree of resistance than others, a few tropical
species being accredited with exceptional durability. The exact nature
of the repellent properties which protect them against borer attack is
not clearly known although the presence of various natural substances
in timbers has been shown to inhibit the activity of borers serving either
as deterrent agents or as mechanical obstruction.
In the search for a wood that may resist the attack of shipworms,
man has tried every type of timber. The details of these elaborate tests
are recorded in the annals of harbour engineers from all over the world.
These show that some species of timbers exhibit unusual resistance to
boring animals, this factor being linked to certain specific properties of
the timber. This may purely be on account of the structure or hardness
of timbers (Kooy, 1922; Rivera, 1922; Johnson, 1932; Moll, 1948a) or
owing to the presence in them of certain deterrent substances (Theophrastus, 1495-98 ; Montanus, 1671) and more specifically resinous
materials (Sellius, 1733; Cram, 1873; De Coque, 1895; Hoech, 1896;
Valder, 1904 ;Rivera, 1922 ; FitzsimonsandBrooks, 1920; Baldwin, 1938;
Moll, 1948), alkaloids (Iterson, 1934; Fitzsimons andBrooks, $920; Barger,
1922,1924 ; Kooy, 1922 ; Record and Mell, 1924 ; Bianchi, 1933 ; Iterson,
1934; Baldwin, 1938; Spoon and Loosjes, 1946; Bavendamm, 1948;
Bavendamm and Schmidt, 1948 ; Moll, 1948a, Edmondson, 1955),
poisonous inclusions (Bavendamm, 1948), tannins (Moll, 1948 ; Edmondson, 1955), gummy deposits (Anon, 1862 ; Edmondson, 1947),
waxy materials or oily substances (Fitzsimons and Brooks, 1920 ;
Money, 1811; Jarvis, 1904) ineither thebark orthe body of timber have
been cited as responsible for the general durability of certain timbers
N . BALAKRISHNAN NAIR AND M. SARASWATHY
Perhaps the most economical and effective method for checking
ravages of shipworms may be the least tried, namely biological control.
Several predators, parasites and associates of unknown relationship are
known from shipworms (vide supra) such as protozoans, planarians and
polychaetes. Some of these are known to attack and devour them piecemeal.
Despite man’s ceaseless fight against shipworms, with all available
resources and techniques, their relentless destruction continues and a
thorough re-orientation in our techniques of warfare has become
imperative. The discovery of an effective panacea depends on a better
understanding of the ecology of these specialized bivalves.
XX. TIMBERS OF UNUSUAL DITRABILITY AGAINST SHIPWORMS
No woods have been shown to be indefinitely immune to the
destructive activity of shipworms. However, certain timbers are known
t o possess a greater degree of resistance than others, a few tropical
species being accredited with exceptional durability. The exact nature
of the repellent properties which protect them against borer attack is
not clearly known although the presence of various natural substances
in timbers has been shown to inhibit the activity of borers serving either
as deterrent agents or as mechanical obstruction.
In the search for a wood that may resist the attack of shipworms,
man has tried every type of timber. The details of these elaborate tests
are recorded in the annals of harbour engineers from all over the world.
These show that some species of timbers exhibit unusual resistance to
boring animals, this factor being linked to certain specific properties of
the timber. This may purely be on account of the structure or hardness
of timbers (Kooy, 1922; Rivera, 1922; Johnson, 1932; Moll, 1948a) or
owing to the presence in them of certain deterrent substances (Theophrastus, 1495-98 ; Montanus, 1671) and more specifically resinous
materials (Sellius, 1733; Cram, 1873; De Coque, 1895; Hoech, 1896;
Valder, 1904 ;Rivera, 1922 ; FitzsimonsandBrooks, 1920; Baldwin, 1938;
Moll, 1948), alkaloids (Iterson, 1934; Fitzsimons andBrooks, $920; Barger,
1922,1924 ; Kooy, 1922 ; Record and Mell, 1924 ; Bianchi, 1933 ; Iterson,
1934; Baldwin, 1938; Spoon and Loosjes, 1946; Bavendamm, 1948;
Bavendamm and Schmidt, 1948 ; Moll, 1948a, Edmondson, 1955),
poisonous inclusions (Bavendamm, 1948), tannins (Moll, 1948 ; Edmondson, 1955), gummy deposits (Anon, 1862 ; Edmondson, 1947),
waxy materials or oily substances (Fitzsimons and Brooks, 1920 ;
Money, 1811; Jarvis, 1904) ineither thebark orthe body of timber have
been cited as responsible for the general durability of certain timbers