From the observations made by Réaumur, he concluded that the mother-fly, above described, deposits her eggs in the flesh of the larger animals, for which purpose she is furnished with an ovipositor of singular mechanism. We have seen that the ovipositors in the gall-flies (_Cynips_) are rolled up within the body of the insect somewhat like the spring of a watch, so that they can be thrust out to more than double their apparent length. To effect the same purpose, the ovipositor of the ox-fly lengthens, by a series of sliding tubes, precisely like an opera-glass. There are four of these tubes, as may be seen by pressing the belly of the fly till they come into view. Like other ovipositors of this sort, they are composed of a horny substance; but the terminal piece is very different indeed from the same part in the gall-flies, the tree-hoppers (_Cicadæ_), and the ichneumons, being composed of five points, three of which are longer than the other two, and at first sight not unlike a _fleur-de-lis_, though, upon narrower inspection, they may be discovered to terminate in curved points, somewhat like the claw of a cat. The two shorter pieces are also pointed, but not curved; and by the union of the five, a tube is composed for the passage of the eggs. It would be necessary, Réaumur confesses, to see the fly employ this instrument to understand in what manner it acts, though he is disposed to consider it fit for boring through the hides of cattle. "Whenever I have succeeded," he adds, "in seeing these insects at work, they have usually shown that they proceeded quite differently from what I had imagined; but unfortunately I have never been able to see one of them pierce the hide of a cow under my eyes."[GJ] [Illustration: Ovipositor of the Breeze-fly, greatly magnified, with a claw and part of the tube, distinct.]