We will now give a hasty glance at the different groups of mites, pausing to note those most interesting from their habits or relation to man.
The most highly organized mite (and by its structure most closely allied to the spider) is the little red garden mite, belonging to the genus Trombidium, to which the genus Tetranychus is also nearly related. Our own species of the former genus have not been "worked up," or in other words identified and described, so that whether the European T. holosericeum Linn. is our species or not, we cannot tell. The larvæ of this and similar species are known to live parasitically upon Harvestmen (Phalangium), often called Daddy-long-legs; and upon Aphides, grasshoppers and other insects. Mr. Riley has made known to us through the "American Naturalist" (and from his account our information is taken), the habits of certain young of the garden mite (Trombidium) which are excessively annoying in the Southwestern States. The first is the Leptus? Americanus (Fig. 145), or American Harvest mite. It is only known as yet in the larval or Leptus state, when it is of the form indicated in the cut, and brick red in color. "This species is barely visible with the naked eye, moves readily and is found more frequently upon children than upon adults. It lives mostly on the scalp and under the arm pits, but is frequently found on the other parts of the body. It does not bury itself in the flesh, but simply insinuates the anterior part of the body just under the skin, thereby causing intense irritation, followed by a little red pimple. As with our common ticks, the irritation lasts only while the animal is securing itself, and its presence would afterwards scarcely be noticed but for the pimple which results."
145 a. American Harvest Mite; b. Irritating Harvest Mite; the dots underneath indicating the natural size.
The second species (Fig. 145 b, Leptus? irritans) is also only known in the Leptus stage. It is evidently the larva of a distinct genus from the other form, having enormous maxillæ and a broad body; it is also brick red. Mr. Riley says that "this is the most troublesome and, perhaps, best known of the two, causing intense irritation and swelling on all parts of the body, but more especially on the legs and around the ankles. Woe betide the person who, after bathing in the Mississippi anywhere in this latitude, is lured to some green dressing-spot of weeds or grass! He may, for the time, consider himself fortunate in getting rid of mud and dirt, but he will afterwards find to his sorrow that he exchanged them for something far more tenacious in these microscopic Harvest-mites. If he has obtained a good supply of them, he will in a few hours begin to suffer from severe itching, and for the next two or three days will be likely to scratch until his limbs are sore.
"With the strong mandibles and the elbowed maxillæ which act like arms, this mite is able to bury itself completely in the flesh, thereby causing a red swelling with a pale pustulous centre containing watery matter. If, in scratching, he is fortunate enough to remove the mite before it enters, the part soon heals. But otherwise the irritation lasts for two, three or four days, the pustulous centre reappearing as often as it is broken.
"The animal itself, on account of its minute size, is seldom seen, and the uninitiated, when first troubled with it, are often alarmed at the symptoms and at a loss to account for them. Fortunately these little plagues never attach themselves to persons in such immense numbers as do sometimes young or so-called 'seed' ticks; but I have known cases where, from the irritation and consequent scratching, the flesh had the appearance of being covered with ulcers; and in some localities, where these pests most abound, sulphur is often sprinkled during 'jigger' season in the boots or shoes as a protection.
"Sulphur ointment is the best remedy against the effects of either of these mites, though when that cannot be obtained, saleratus water and salt water will partially allay the irritation.
"The normal food of either must, apparently, consist of the juices of plants, and the love of blood proves ruinous to those individuals who get a chance to indulge it. For unlike the true Jigger, the female of which deposits eggs in the wound she makes, these Harvest-mites have no object of the kind, and when not killed by the hands of those they torment, they soon die victims to their sanguinary appetite."
