I hope that the reader will not be sorry to meet with an extract from the pamphlet which was the starting-point of my own researches, the more so that it is necessary for the understanding of what follows. So I will let my Master speak, only abridging slightly:— In all insect history I know of no fact more curious and extraordinary than that which I am about to relate. It concerns a species of Cerceris which feeds its progeny on the most splendid kinds of Buprestis. Let me share with you, my friend, the vivid impressions gained by studying the habits of this Hymenopteron. In July 1839 a friend, who lives in the country, sent me two Buprestis bifasciata, an insect new to my collection, telling me that a kind of wasp which was carrying one of these pretty beetles had dropped it on his coat, and that a few minutes later a similar wasp had let fall another on the ground. In July 1840, having been called in as physician by my friend, I reminded him of his capture of the preceding year, and asked about the circumstances. Season and place corresponding with it, I hoped to do as much myself, but that particular day was dark and chilly, unfavourable therefore to the flight of Hymenoptera. Nevertheless, we made a tour of inspection in the garden walks, and seeing no insects I bethought myself of seeking in the ground for the homes of burrowing Hymenoptera. A tiny heap of sand recently thrown up, like a miniature mole-hill, attracted my attention. Scratching it away, I saw that it masked the orifice of a gallery descending far down. We carefully dug up the ground with a spade, and soon caught sight of the shining elytra of the coveted Buprestis. Soon I not only found wing-cases but a whole Buprestis, nay, three and four displayed their gold and emerald. I could not believe my eyes. But that was only the prelude to my feast. In the chaos caused by my own exhumations a Hymenopteron appeared and was taken by me; it was the captor of the Buprestis, trying to escape from amid her victims. I recognised an old acquaintance, a Cerceris which I have found some two hundred times in Spain and around Saint Sever.