Amongst the parasitic insects a great variety of microscopic subjects will be found. As these are usually small, they may be killed by immersion in spirits of turpentine; and if at all opaque, may be allowed to remain in the liquid until transparent enough, and then mounted in Canada balsam. The acarida, or _mites_ and _ticks_, are well known; none, perhaps, better than those which are so often found upon cheese. Flour, sugar, figs, and other eatables, are much infested by them; whilst the diseases called the _itch_ in man, and the _mange_ in animals, are produced by creatures belonging to this tribe. These animals are sometimes mounted by simply steeping them in turpentine, and proceeding as with other insects. The “Micrographic Dictionary” gives the following directions as to mounting _parts_ of these:--“The parts of the mouth and the legs, upon which the characters are usually founded, may be best made out by crushing the animals upon a slide with a thin glass cover, and washing away the exuding substance with water; sometimes hot solution of potash is requisite, with the subsequent addition of acetic acid, and further washing. When afterwards dried and immersed in Canada balsam, the various parts become beautifully distinct, and may be permanently preserved.” Feathers of different kinds of birds are usually mounted in balsam when required to show much of the structure. This is particularly interesting when the feathers are small, as they then show the inner substance, or _pith_, as it may be termed, with the cells, &c. The “pinnæ,” or soft branches of the feathers, will be found of various constructions; some possessing hooks along one side, whereby they fasten themselves to their neighbours; others branching out, with straight points somewhat resembling the hairs from certain caterpillars. But, of course, when the metallic-looking gorgeous colours are all that is required to be shown, and reflected light used (as with the feathers of the hummingbird, peacock, &c.), it is much better that they should be mounted dry, as in Chapter II. The _seeds_ and _pollen_ of plants are most frequently mounted dry, as mentioned in Chapter II.; but the more transparent of the former, and the darker kinds of the latter, are perhaps better seen in Canada balsam. There is nothing particular to be observed in the manipulation, except that the glass cover must be applied lightly, otherwise the grains may be crushed. There are some objects which cannot be shown in a perfect manner when mounted _dry_, but when immersed in balsam become so very transparent that they are almost useless. To avoid this, it has been recommended to stain the objects any colour that may be convenient, and afterwards mount in balsam in the ordinary manner.