to mistake a species of the long-bodied caterpillars, for one of the short-bodied; the difference being extremely apparent at the first glance. "These reasons appear to me so convincing, I should have thought myself inexcuseable to have passed them over in silence, when I was giving the history of these animals. I shall therefore think myself happy to have this circumstance corroborated by future experience, or rectified and cleared up, if found to be an error. I shall only say, I have dwelt the longer on it, as it is an observation I never heard of before. I have likewise singled out the largest Libella, and the flat-bodied ones for its illustration, as being more conspicuous by their size, and easier to be observed than those of the smaller sorts. "The two principles of hunger and lust, so apparent through the animal kingdom, are in no class or tribe more manifest and visible than in these insects. The former I have described and explained through their different states; it remains for me to shew the manner in which they obey the calls of the latter. And herein I must observe, that the different manner in which the act of copulation is performed, depends on the difference of the respective kinds; the organs of generation being placed in different parts of the body, according to the distinct species. All the flat-bodied ones have those parts placed in common with most other insects, at the extremity of the tail. In all the slender-bodied ones, the organ of the male is placed next the breast, close to the part where the thorax and abdomen unite; while the same organ in the female lies in the very extremity of the tail, and the singular manner of these creatures coupling is a circumstance worthy of observation.