Whether Economic Entomology can be an exact science is, I think, a question in which we should all be interested. I propose therefore to examine it with the care that it deserves though I will try to make the discussion as brief as possible.

Broadlly speaking, the sciences can be divided into two classes: the speculative sciences, whose object is simply the discovery of truth: new facts or new laws; and the practical sciences, whose objest is the production of facts: causing something new to happen.