Page:Jardine Naturalist's library Entomology.djvu/187

Rh Touch is the sense most generally diffused over the bodies of the higher animals, and it seems equally dispersed among insects; but the hard covering of the latter must often render it very obtuse, except in particular places. In the soft bodies of many larvæ, it is true, the skin is so delicate that it may well be susceptible of the finest impressions, and capable of transmitting the most vivid sensations; this power, besides, is often greatly aided, in such cases, by the hairs usually scattered over the surface. But though the rigid covering may often produce comparative insensibility, or merely give indication of the presence of bodies, this sense is always so concentrated in certain organs as to intimate the properties of material objects, such as form, size, density, &c. The organs in which it is most perfect are undoubtedly the palpi. Their articulated structure adapts them for being closely applied to bodies; the delicate membrane which often covers their extremity is particularly fitted for receiving impressions; they are supplied with a considerable nervous branch; and they are observed to be continually applied by the insect to the objects with which it comes in contact. At the same time there can be little doubt that the same function is performed more or less perfectly by other parts, such as the tarsi, the spiral proboscis of Lepidoptera, the haustellum of Diptera, and in most tribes more especially by the antennæ. Whoever has watched the antennæ of a hive-bee, an ant, or an ichneumon, when engaged in any operation in which it is interested, will be surprised that ever it could be doubted