The _Ptinus_ group embraces _Ptinus fur_, _Ptinus mollis_, _Ptinus brunneus_, and _Ptilinus pectinicornis_, called by Leunis "_Bücherbohrer_." According to Butler, a peculiarity of this genius--that of dissimilarity of shape between the sexes--is well illustrated by the _P. fur_, the male being almost cylindrical, the female inflated or rounded at the sides; so much variation that they might be taken for two different insects. _Ptinus brunneus_, although similar to _P. fur_, is distinguished from it by being wholly of a light-brown color and destitute of whitish bands on the wing covers. Some writers speak of this species as the "book beetle," while _Sitodrepa_ is spoken of as the "spice beetle." Dr. Henry Shimer makes the following statement regarding their method of boring: "They usually operate in leather-bound or half-bound volumes by boring galleries along in the leather.... They usually bore along quite under the surface of the leather, cutting it almost through; occasionally a small round hole penetrates through the leather to the outer surface." One of the most famous cases on record of insects boring through books is that reported by M. Peignot, in which he states that twenty-seven folio volumes were pierced through in so straight a line that a cord might be passed through them and all the volumes raised by means of it. Different writers give the credit of this feat to different members of this group, so that the most that can be said is that it was the work of some member of the _Ptinidæ_. In the family _Scolytidæ_ only one species belongs to the book ravagers. It is known as _Hypothemus eruditus_, and was described by Westwood in 1836 as "pitchy black, the head of the same color, entirely concealed from above by the front thorax." It is very minute in size, being about one twentieth of an inch in length. So far as its depredations have been observed it confines its work to the bindings of books, making furrows in all directions much as it does in the sap wood of dead trees. The strong resemblance of its burrowing to the gouging done by an engraver's chisel has given to this family the name of "engraver beetles."