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A Menace in the Harbour

Mike Wilson, Local Author and Historian

From Bridlington Quay and Neighbourhood by Thomas Cape

Printed and published at Furby's 'Observer' Offices, King Street. 1877

Timber-Eating Insects in the Harbour

A peculiar cause of injury to the jettying and other wood-work in the harbour arises from a small but destructive insect.

In a chapter headed "Indirect injuries caused by insects," in Kirby and Spence's "Introduction to Entomology," the following account is given by Mr Spence. "The Linnaean order Aptora furnishes another timber-eating insect, a kind of wood-louse (Limnoria terebrans of Dr Leach), which though scarcely an eighth of the size of the common one, in point of rapidity of execution seems to surpass all its European brethren, and in many cases may be productive of more serious injury than any of them, since it attacks the wood-work of piers and jetties constructed in salt water, and so effectually, as to threaten the rapid destruction of those in which it has established itself. In December, 1815, I was favoured by Charles Lutwidge, Esq, of Hull, with specimens of wood from the piers at Bridlington-Quay which woefully confirm the fears entertained of their total ruin by the hosts of these pigmy assailants that have made good a lodgment in them, and which, though not so big as a grain of rice, ply their masticatory organs with such assiduity as to have reduced a great part of the wood-work which constitutes their food into a state resembling honeycomb.

Our specimen was a portion of a three-inch plank nailed to the North Pier about three years before, which is crumbled away to less than an inch in thickness – in fact, deducting the space occupied by the cells, which cover both surfaces as closely as possible, barely half an inch of solid wood is left; and though its progress is slower in oak, that wood is equally liable to be attacked by it.*

If this insect were easily introduced to new stations, it might soon prove as destructive to our jetties as the Toredo navalis to those of Holland, and induce the necessity of substituting stone for wood universally, whatever the expense, but happily it seems endowed with very limited powers of migration; for, though it has spread along both the South and East Piers of Bridlington harbour, it has not yet, as Mr Lutwidge informs me, reached the dolphin nor an insulated jetty within the harbour. No other remedy against its attacks is known than that of keeping the wood free from salt water for three or four days, in which case it dies; but this method, it is obvious, can be rarely practicable.†"

From the manner in which the foregoing is written, one might suppose that the insect was, at that time, peculiar to Bridlington. Be that as it may, the fact is well known that now [1876] it is found at Yarmouth, Scarborough, and other places on the coast. Lloyd's agent here and also the harbour-master, state that a method is now in use which, properly done, completely checks the ravages of these little insects; it is by driving nails, thickly placed, into the wood; these nails are specially prepared for the purpose, the heads of which measure more than an inch in diameter; the surface of the wood thus covered is, of course, protected, and the small spaces between, becoming impregnated with the rust from the iron, are safe from their attacks, as they are never known to bore wood in this state; it being apparently distasteful to them. Since Mr Lutwidge wrote to Mr Spence, the insulated jetty has been severely used, some of the piles are actually eaten through, and had it not been protected by some new stays of oak, would not at this time have been standing. The dolphins have not escaped. The prevailing opinion as to the introduction of this insect to Bridlington is, that it was brought by a vessel somewhat infested, which came from a foreign port.

*Dr Moore, in Magazine of Natural History, N.S. ii 206, states that its injurious effects have been known at least forty years in the harbour at Plymouth, where it is called 'gribble.'

†"In order to ascertain how far pure sea water is essential to this insect, and consequently what danger exists of its being introduced into the wood-work of our docks and piers communicating with our salt water rivers, as at Hull, Liverpool, Bristol, Ipswich, &c., where it might be far more injurious than even on the coast, I have since December 15th, 1815, when Mr Lutwidge was so kind as to furnish me with a piece of oak full of the insects in a living state, poured a weak solution of common salt over the wood every other day, so as to keep the insects constantly wet. On examining it this day (February 5th, 1816) I found them alive; and, what seemed to prove them in as good health as in their natural habitat numbers have established themselves in a piece of fir wood which I nailed to the oak, and have in this short interval, and in winter too, bored many cells in it."

The gribble – according to Bridlington Harbour, its plants and animals, published in 1981 by a group of students of the Department of Adult Education in the University of Hull – is 5mm long, having seven pairs of legs with sharp claws to hold the beast whilst it bites into the wood. The female leads, doing the burrowing with her jaws. The gribble bores into pier piles, boats, etc., causing thousands of pounds worth of damage.