A review of the different families of insects whose habits under favorable conditions lead them to infest books and bindings will show them to be more or less well defined according to their feeding habits. The book scorpions and mite, _Cheyletus eruditus_, which, as we have seen, do not come under the head of insects, are primarily carnivorous, and their presence in books may be due to the fact that they find there animal as well as vegetable food. This is certainly true of the book scorpion, which feeds on mites, book lice, and other small insects. The "fish moths" or "silver fish," the "book lice," and the "cockroaches" can have no other reason for infesting books than their liking for farinaceous substances such as are used in and about the bindings and labels of books. For this reason the damage done by them is largely confined to the exterior or interior of the bindings, and only so much of the book itself is injured as comes in their way in their search for food. The "white ants" feed principally on wood, and in and about books there is more or less wood fiber which would be to the liking of these voracious feeders. The moths and beetles are the burrowers and borers. They seek retired places in which to lay their eggs where the larvæ will be surrounded with food for their growth. The moths and some of the beetles are more given to burrowing in the bindings, keeping close to the outer surface for the purpose, it is thought, of making it easy for the imago to emerge after the change is completed; while others bore straight tunnels often from cover to cover. A natural conclusion for one who has gone over the literature of book-injuring pests to reach is that the many persons that have been industriously looking for the bookworm, as well as those that have reported the finding of isolated specimens, some dead, some alive, have had in mind the one creature which bored holes in books. The frequent use of the terms "genuine bookworm," "the real bookworm," etc., reveals the fact that the users of these phrases approached the subject with a preconceived idea of the kind of creature they should find to account for the ravages only too apparent on scores of volumes which pass through the hands of booksellers and book keepers. To many the boring beetles are the only creatures which are rightfully called bookworms, and in their search other book pests have not been taken into account. HYDROPHOBIA IN BAJA CALIFORNIA. BY DANE COOLIDGE.