The largest number of book-destroying insects are found among the beetles, of the order _Coleoptera_. To this group belong the "book borers." The species thus far considered have been more or less dilettantes in literature. The beetles, however, seem possessed with a true spirit of investigation, and when they undertake a piece of work in a serious fashion they go to the bottom of it, sticking close to the line laid down. This characteristic distinguishes these insects from all others, and makes it comparatively easy to determine when they have been at work in a worm-eaten volume. No less than sixteen different species of this order have been either detected in this work, or such strong circumstantial evidence has been found against them, that there is little doubt as to their guilt. Some insects seem to destroy books for the sheer want of something better to do; some do so in seeking the paste and sizing used in and about the books; others because the leather bindings are desirable material in which to undergo transformation; and, again, others haunt book shelves and books in search of prey in the form of living creatures. But among the beetles are found tiny little grubs that seem to have a genuine intent to destroy; that set out deliberately to wreak vengeance on man's record of his thoughts, deeds, and discoveries, and, as if knowing the means which man uses to destroy, have sought to imitate him in the effects produced. As a result we find books filled with small, round, shotlike holes strongly suggesting the results which might follow from the use of the family Bible by the restless boy as a target for his first shotgun. The book-destroying beetles are all grouped under three families: _Dermestidæ_, _Scolytidæ_, and _Ptinidæ_. The _Dermestidæ_ include the "flower beetles" and the well-known "carpet bug." The species of which there can be no doubt as to its disposition to pierce book bindings is _Anthrenus varius_, which Glover says "is a very pretty insect when examined under a magnifying glass, being beautifully marbled or variegated with black and gray." Another member of this family, against which there is less evidence, is _Dermestes chinensis_, so named by Dr. L'Herminier, of Guadeloupe, who reported a loss of nearly four hundred volumes from its ravages. Erichson believes this to have been the well-known _Anobium paniceum_. _Dermestes lardarius_ and _Attagenus pellio_ are others of this family mentioned in the same category.