BOOKWORMS — BACK 373 



subterranean termites are indicated in plates 9 and 10. No two 

 books will show the same pattern of destruction, but subterranean 

 termite injury can be identified by the thin deposit of mud with 

 which the termites line the cavities eaten out in books. This mud 

 is formed from earth particles carried from the soil beneath the 

 building in which the damage has occurred and is used as a plaster 

 to air-condition the termite home. 



Dry-wood termites require no contact with the soil and may be 

 destructive wherever they occur. Fortunately, instead of being 

 found in most parts of the United States as are the subterranean 

 termites, they are more tropical forms and are found mainly in 

 tropical areas, being troublesome in the United States from Charles- 

 ton, S. C, southward. In southern Florida, Cuba, and parts of 

 California, and in Hawaii and the Philippine Islands, they are de- 

 structive. They do not line with mud the cavities they eat in books, 

 but can be identified at once by the peculiar appressed whitish or tan 

 pellets of excrement which will flow in a stream from a book as it is 

 opened (pi. 3, b). The cavities that they eat into books are of endless 

 variation as to size and contour (pi. 11). 



Although more instances of injury by insects to books have been 

 recorded during the past few years in private homes, the ravages 

 of book insects have been greatly lessened in large public and private 

 institutions, where much attention is being given to perfecting 

 methods designed to eliminate insects. Subterranean termites have 

 been eliminated from modern termite-proofed buildings using steel 

 shelving. Modern construction and care in selecting shelving with- 

 out open hollow spaces that can be used as hiding places for cock- 

 roaches and silverfish make possible the complete subjection of these 

 defacers of books in most parts of the country. The National 

 Archives has installed modern vacuum fumigation vaults in which 

 every lot of newly acquired material is fumigated for the destruction 

 of insects before it is allowed to be unpacked. These steel vaults, 

 two in number, are shown in plate 18. Each vault is 4i^ by 5i^ by 11 

 feet. As told by Arthur E. Kimberly, Chief of the Archives' Divi- 

 sion of Repair and Preservation : 



The records are placed in a vault in their original containers and the vault 

 Is evacuated until a vacuum of approximately 29.9 in. of mercury is obtained. 

 A mixture of ethylene oxide and carbon dioxide is then released into the cham- 

 ber until the vacuum falls to 21 in. of mercury. The gas is then agitated for 

 15 minutes by pumping it out at the top and in at the sides of the chamber. 

 After the records have been exposed for a total of 3 hours the chamber is reevac- 

 uated to 29.8 in. of mercury, the vacuum is broken with air, and the fumigated 

 materials are removed. 



This method was developed for destroying insects in agricultural 

 products by the experts of the Bureau of Entomology and Plant 



