That too much stress has been laid upon the significance of the enlarged jaws and other hypertrophied developments in the Beetles seems to be shown by the case of certain carnivorous Beetles, of which one species (_Taphroderes distortus_) may serve as an example. Herein the left jaw takes the form of a long, crooked strap-shaped outgrowth, whose purpose cannot even be conjectured. And in this connection one may cite the case of certain species of Homoptera—Bugs—which occur in tropical South America. Here, in both sexes, as may be seen in Plate 40, Fig. 4, the neck-shield is produced backwards far beyond the body, to form a most elaborate superstructure which appears to confound the most ingenious attempts at interpretation. It is to be noted that wherever special structures are necessary for the performance of specific acts such as are of vital importance to the well-being of the race, they are developed to perfection: there is little or no variation in their size, and no doubt as to their purpose. Thus in many species means are necessary to enable the male to seize and hold the female during the sexual embrace. In the Water Beetle of our ponds and ditches (_Dytiscus marginalis_) the male bears a very remarkable sucker on each fore-leg, the adhesive surface of which, under the microscope, reveals an extraordinary complexity and wondrous beauty. This sucker forms a very conspicuous “secondary sexual character,” and is used in embracing his mate, whose back is deeply grooved to enhance the hold of the suckers. In some species punctures take the place of grooves. Suckers, like those of _Dytiscus_ are met with again in a Wasp (_Crabro cribrarius_). In another genus of Beetles (_Penthe_) cited by Darwin, the antennæ of the male have a few of the middle joints dilated and their under surfaces furnished with a cushion of hairs to aid in the sexual embrace. Beetles are creatures of solitary habits; how, then, do they find their mates when, by the insistence of the reproductive desires, they are driven forth to begin the search? Though we have no direct evidence, it seems more than probable that, as with the Butterflies and Moths, scent furnishes their most reliable guide. At any rate, in a large number of species, as among the Lamellicornia, the antennæ bear leaf-like plates, which are much more developed in the males, in which they probably serve as scent-detecting organs. In some species stridulating organs occur such as are met with in even greater perfection among the Crickets and Grasshoppers, and among the Spiders and Scorpions. That these “musical-boxes” provide a means of communication between the sexes there can be no doubt, even if, as some contend, they are commonly used only to frighten enemies. This purpose may well be the explanation of their presence in the larval Stag Beetle, for it cannot be claimed that they have any relation to the acts of courtship at this stage of development.