STONE AND WOOD BORERS 347 



very large series of smaller grubs and adult insects which 

 injure trees or bore or devour wood already cut and dried. 

 Among these are the saw-flies and a number of beetles, 

 and in Sicily and the tropics there are the wonderful white 

 ants which are not ants at all, but more like May-flies. 

 The destruction caused by these borers and eaters of 

 wood is increased by the fact that when they have riddled 

 a piece of wood, moisture penetrates it, and vegetable 

 " moulds " flourish within it and complete the break-up. 

 Among the most destructive borers of wood are those 

 which attack the ships and piers of wood placed by man 

 in the sea. These are certain shell-fish, called ship-worms 

 (Teredo), which are really peculiarly modified mussels. 

 There is also a tiny shrimp-like creature, the Limnoria 

 terebrans, which does enormous damage by its borings to 

 piers of wood erected in the sea. True insects do not 

 flourish in the sea. There are marine bivalve shell-fish 

 which bore into clay, sandstone, chalk, and even into hard 

 granite-like rock. They do not use jaws or teeth for this 

 purpose, but the surface of their shells, which are sharp 

 and spiny, and also the sand which adheres to their soft 

 muscular bodies like emery powder to the pewter-plate of 

 a lapidary's wheel. You may see the large and small 

 holes made by Pholas (called also " the piddock ") and 

 other bivalve shell-fish in the clay and chalk rocks of the 

 seashore on most parts of the English coast. 



Most boring animals swallow the material which they 

 excavate in the act of boring, just as the earth-worm 

 swallows the soil into which it bores, and as many sand- 

 worms do, throwing out from the hind end of the body, 

 in the form of a little coiled-up heap, a vast quantity of 

 undigested matter which has passed through them. But 

 many insects which swallow some of the material dis- 

 engaged by their jaws remove, in addition, a large 

 quantity which is ejected from the boring as powder, like 



