622 



Destructive Insects in Timber. 



[JAN., 



place for egg-laying crevices or cracks in dry wood. It does 

 not confine its attention to one species of timber, but lays in- 

 differently in many kinds of wood. Infestation is most likely 

 where the timber has not been "impregnated," or treated with 

 material to combat the attacks of insects and fungi, and is also 

 most frequent in timber that has a marked alburnum or sap 

 wood. From the eggs of the beetle hatch out grubs that have 

 a curled wrinkled body and hard biting jaws. These grubs, 

 when full fed, become pupae in the burrows in the wood, and 

 after a, resting stage, differing in length according to the con- 

 ditions, the beetles of the next generation are produced and 

 proceed to a new egg-laying 



Preventive and Remedial Treatment. — Apart from the 

 general principles of not allowing the timber, when cut, to be 

 long exposed, measures should be adopted to render the wood 

 unlikely to be attacked by the beetles or other insects (or fungi). 

 The protective measures to be adopted will vary with the pur- 

 pose for which the timber has to be applied : e.g., if for outside 

 purposes, such as railway sleepers, creosoting is practised with 

 success. Timber used for inside purposes can be rendered insect 

 proof by its being either steeped in or painted over with such 

 poisonous materials as sulphate of copper (wood so treated 

 becomes somewhat brittle), or chloride of zinc (a 2 to 3 per 

 cent, solution), or corrosive sublimate (this is a dangerous poison, 

 which must be borne in mind if the timber so treated is required 

 for use in houses). Whichever of these substances be used, a 

 solution in methylated spirits (90 per cent, alcohol) is recom- 

 mended in preference to an aqueous solution, as the former 

 soaks in more readily. 



To kill the insects (grubs and beetles) in timber found to be 

 infested, the wood should be painted over with, or steeped in, the 

 following : — 780 grains naphthalene, 80 grains corrosive subli- 

 mate (very poisonous), 1 \ pints methylated spirits. 



In painting the wood with this material care should be taken 

 to give special attention to the crevices. 



This is the most thorough way to prevent the spreading of the 

 pest, as it should kill out the colonies, which are the centres from 

 which the infestation is carried to freshly introduced timber. 

 Unless this be done, the danger of new wood being attacked 

 must continue. 



