Works on entomology gave the general statement that this insect emitted the frothy mass from its body. Curious to ascertain what peculiar gas-secreting apparatus was contained within its anatomy, I dissected a number of specimens, without finding a trace of any structure that could produce from within the body a single bubble of air. On the contrary, I found that the little insect emitted a clear, somewhat viscid fluid, and by means of appendages at the extreme tip of its tail secured a moiety of air by grasping it, so to speak, and then instantly releasing it as a bubble in the fluid it had secreted. At the time of this observation--twenty-five years ago--I supposed that entomologists were familiar with this fact, but, on the appearance of my little book, I received a letter from the late Dr. Hermann Hagen, the distinguished entomologist, stating that he had ransacked his library and failed to find any reference of the nature of my statement. Doubtless the whole history of this insect has since been published, but a somewhat superficial survey of the literature has failed to reveal any reference to the matter. In this connection it is interesting to observe how often the more easily accessible facts of Nature escape the special student. The history of science is replete with such instances. One can hardly take up any subject connected with the life history of animals without finding lacunæ which ought to have been filled long ago. The facts in regard to the ossification of the hyoid bones in man is a case in point. The persistence of these erroneous concepts or half-truths comes about by the acceptance at the outset of some fairly trustworthy account by an authority on the subject, and ever after the statements are copied without a doubt being expressed as to their accuracy.