But one does not perceive the galleries excavated by these annoying insects, positive tunnels or covered ways, through which they proceed to pour forth elsewhere the superfluity of their numerous progeny. Less prolific than the _Acari_, which create upon the skin immense patches of irritation, the harvest bugs confine themselves to a few circumscribed localities: their favourite choice being the legs, the arms, and the corners of the eyes, especially among young children. They are not above domestic animals; cats and dogs frequently suffer from them,--not, indeed, over the whole surface of the body, for they are not so wandering as the _Acari_,--but particularly inside the shell of the ear. At the first glance you would scarcely believe that those red points, apparently immovable, could be living beings,--could be animals belonging to an order of some importance. * * * * * Let us attempt to isolate one of the animalcules with the point of a pin: it is not an easy thing to do, because they usually adhere to the epidermis in clusters of three or four individuals. There, now we have succeeded, and here is one before us: it is only the fifth of a millimètre in diameter, which is, for most people, the very last limit of the visual function (see the small white line in Fig. 76, _a_). And, in truth, it _would_ be imperceptible to the eye but for its bright red colour. To study it carefully, of course, you must make use of a very strong lens, or, rather, of a microscope. (See Fig. 76, _b_.) [Illustration: FIG. 76.--_a Leptus Autumnalis_ (nat. size). _b_ Ditto (mag.).] To this tiny animal has been given the name of _Leptus autumnalis_; the first, on account of its extreme delicacy; the second, because it is visible up to the end of autumn. When examined through a microscope, it produces on the spectator the impression of a spider; but, like all other insects, it has only six legs. Our naturalists, however, have found some difficulty in classifying it; and by way of cutting the Gordian knot of their embarrassments, some have placed it in a separate family of _Microphthiræ_ (literally "little lice"), which is made to include all Arachnidæ with six legs. Others, who regard the wheat worm as an insect, rank it among the parasitical Apteræ.