Page:Jardine Naturalist's library Entomology.djvu/148

142 stages of development. The striking changes in outward appearance implied by the terms complete metamorphosis, prepare us to expect some corresponding alteration in internal organs, and this, accordingly is found to be the case. The proportions of the different parts are not only different, but some of the parts found in the perfect insect are wanting in the larva, while others exist which disappear in the final stage. Such changes are indispensable when the larva lives on one kind of food, and the imago on another, (as in the Lepidoptera, for example,) but they likewise occur in cases when the food is the same in both conditions. In the larva of the carnivorous Coleoptera, for instance, which are equally predaceous with the mature insect, the only distinguishable parts of the alimentary canal are the esophagus, a minute crop, a chylific ventricle, and a small gut—the ventricle being perfectly smooth externally. To what an extent this differs from the canal of the imago, will appear from a comparison with that of the common Tiger-beetle (C. campestris), formerly described, and figured on Plate 1st, fig. 2. Many instances of it being comparatively short in the early stages, are to be found in the same order, but in none is this more notable than among the phytophagous Lamellicorn beetles. That of the larva scarcely exceeds the length of the body, all the subordinate parts being absorbed (so to speak) by a capacious stomach filling nearly the whole of the splachnic cavity. This expansive ventricle, after the last metamorphosis, becomes narrow, its component