also, is sometimes used in their holes; hot ashes, spirits of turpentine, and other articles of the same kind, are useful to turn them from their course. When a live coal is dropped in their way they immediately attack it, though hundreds may perish in doing so. They are very sensitive to the light of the sun, which is fatal to them. They seldom move during the day, and then only during cloudy days, choosing then the dark woods or thick grass. Their rate of progression is about two yards in a minute, and in their journeys from place to place they go from four to eight abreast. I have seen a stream of Drivers crossing an open path at six o'clock in the morning, and at six at night their number was undiminished. How long they had been passing before I saw them, or how long it continued, I am not able to say. Their path, from constant travel, became quite worn and smooth. The natives are very careful to remove all grass from the vicinity of their houses, as a means of keeping off these pests.

A CHAPTER ON MITES.

BY A. S. PACKARD, JR.

BUT few naturalists have busied themselves with the study of mites. The honored names of Hermann, Von Heyden, Dugés, Dujardin and Pagenstecher, Nicolet, Koch and Robin, lead the small number who have published papers in scientific journals. After these, and except an occasional note by an amateur microscopist who occasionally—not to speak too irreverently-pauses from his "diatomaniacal" studies, and looks upon a mite simply as a "microscopic object," to be classed in his micrographic Vade Mecum with mounted specimens of sheep's wool, and the hairs of other quadrupeds, a distorted proboscis of a fly, and podura scales, we read but little of mites and their habits. But few

readers of our natural history text-books learn from their pages any definite facts regarding the affinities of these humble creatures, their organization, and the singular metamorphosis a few have been known to pass through. We shall only attempt in the present article to indicate a few of the typical forms of mites, and sketch, with too slight a knowledge to speak with much authority, an imperfect picture of their appearance and modes of living.

Fig. 61.

d

Mites are lowly organized Arachnids. This order of insects is divided into the Spiders, the Scorpions, the Harvestmen and the Mites (Acarina). They have a rounded oval body, without the usual division between the head-thorax and abdomen, observable in spiders; the head, thorax, and abdomen being merged in a single mass. There are four pairs of legs, and the mouthparts consist, as seen in the adjoining figure of a young tick (Fig. 61, young Ixodes albipictus Pack.*), of a pair of maxillæ (c), which in the adult, terminates in a two or threejointed palpus, or feeler; a pair of mandibles (b), often covered with several rows of fine teeth, and ending in three or four larger hooks, and a serrated

comm

labium (a). These parts form a beak which the mite, or tick, insinuates into the flesh of its host, upon the blood of which it subsists. While many of the mites are parasitic on animals, some are known to devour the eggs of insects and other mites, thrusting their beaks into the egg and sucking the contents. We have seen the mite (Nothrus) figured on the following page (Fig. 62) busily engaged in destroying the eggs of the Canker worm, and Dr. Shimer has observed the Acarus? malus sucking the eggs of the Chinch bug. While

* The figure at the bottom on the left represents the adult, fully-gorged tick.

a few mites are injurious to man, the larger part are beneficial, being either parasitic and baneful to other noxious animals, or more directly useful as scavengers, removing decaying animal and vegetable substances.

Fig. 62.

The transformations of the mites are interesting to the philosophic zoologist, since the young of certain forms are remarkably different from the adults, and in reaching the perfect state the mite passes through a metamorphosis more striking than that of many insects. The young on leaving the egg are usually hexapodous, i. e., have six legs, as we have seen in the case of the Ixodes albipictus previously noticed in the NATURALIST (Vol. ii, p. 559). Sometimes, however, as in the case of the larva, as we may call it, of a European species, Typhlodromus pyri (Pl. 6, fig. 4), the adult of which, according to A. Scheuten, is allied to Acarus, and lives under the epidermis of the leaves of the pear, there are but two pairs of legs present, and the body is long, cylindrical and worm-like. Plate 6, fig. 5 represents the four-legged larva of another species of Typhlodromus.

We have had the good fortune to observe the different stages of a bird mite, intermediate in its form between the Acari and Sarcoptes, or Itch-mite. On March 6th, Mr. C. Cooke called my attention to certain little mites (Pl. 6, fig. 1) which were situated on the narrow groove between the main stem of the barb and the outer edge of the barbules of the feathers of the Downy Woodpecker, and subsequently we found the other forms indicated in Plate 6, figs. 2 and 3, in the down under the feathers. These long wormlike mites were evidently the young of the singular Sarcoptes-like mite, represented by figs. 2 and 3 of the plate, as they were found on the same specimen of Woodpecker at about the same date, and it is known that the growth of mites is rapid, the metamorphoses occupying but a few days.