. SCOLYTUS— PTILINUS. 189 



and if once the bark be separated all round the trunk, the tree 

 will instantly die. 



The reader may probably be aware that some of our most skill- 

 ful naturalists have thought that the Scolytus is not so culpable 

 an insect as is generally supposed, and that it does not attack 

 trees until their race is run, and they have begun to show symp- 

 toms of decay. There is great truth in this conjecture, for it is 

 beyond a doubt that if a tree be seriously injured, and begin to 

 droop, the Scolytus is sure to make a lodgment before very long. 

 Grirdled trees, for example, are almost always attacked by this 

 beetle as soon as the effects of the injury are apparent. But, 

 though the female may not lay her eggs in healthy trees, there is 

 little doubt but that she and her mate have aided, in no small 

 degree, in bringing the tree to so diseased a condition. For, as 

 has already been mentioned, the food of the adult, as well as of 

 the imperfect insect, consists of the bark and wood, and in boring 

 the tree for the purpose of feeding, the numerous Scolyti can but 

 enfeeble its constitution, and so bring it to that state of ill health 

 which renders it a fit cradle for the immature beetles. 



There is hardly a grove or a park in the neighborhood of 

 London where the ravages of the Scolytus are not painfully ap- 

 parent, and in Greenwich Park especially, some of the finest trees 

 are riddled with the cylindrical tunnels of this destructive insect. 

 There are several species of Scolytus, each affecting certain trees, 

 so that there is scarcely any tree that can hope to escape from the 

 jaws of some member of this family. 



The well-known worm-eaten appearance of furniture is caused 

 by certain beetles belonging to another family. As may be seen 

 from, the dimensions' of the tunnels, the insects are very small, 

 and their bodies are nearly cylindrical. The ravages which these 

 beetles cause 'are fatal to all who happen to possess old furniture, 

 but Mr. Westwood mentions that one common species, Ptilinus 

 pectinicornis, completely destroyed a new bedpost in the short 

 space of three years. There is but one known method of killing 

 the insects which have already taken possession, and of preventing 

 others from following their example, namely, by injecting a solu- 

 tion of corrosive sublimate into the holes, and then treating the 

 whole of the surface with the same poisonous liquid. I need per- 

 haps scarcely mention, that insects which are popularly called 

 Death-watches, belong to this family. Not only do furniture 



