504 THE POPULAR SCIENCE MONTHLY. 



abound. Prof. Riley names and describes them as follows : T. Ame- 

 ricanus, a mite barely visible to the naked eye, moves readily, and is 

 found more frequently upon children than upon adults. It lives most- 

 ly upon the scalp and. under the armpits, but is frequently found on 

 other parts of the body. It does not bury itself in the flesh, but works 

 its head under the skin, causing irritation, followed by a red pimple. 

 T. irritcms, the best known and most troublesome of the two, causes 

 intense irritation and swelling on all parts of the body, but more es- 

 pecially upon the legs and around the ankles. By the aid of its strong 

 jaws, the lower pair of which are elbowed, it buries itself completely 

 in the flesh, resulting in a red swelling, with a pustule containing 

 watery matter. If the mite be not removed the irritation lasts several 

 days, the pustule refilling as often as it is broken. It is seldom noticed 

 being so small, and the uninitiated are often alarmed at the symptoms. 

 Saleratus water or salt water will allay the irritation, but sulphur 

 ointment effects a speedy cure. 



Another red mite, belonging to a difierent genus, makes itself use- 

 ful by preying on insects. One species, Tromhidium parasiticum 

 (Fig. 2), is found on the house-fly, which in some seasons is so infested 

 that hardly one can be caught that is not loaded with mites clinging 

 to the base of its wings. This or closely related species are found on 

 spiders and mosquitoes, which they help to kill off". One species Dr. 

 Packard found doing good work in eating the plant-lice ofi" his rose- 

 bushes ; another attack the Rocky Mountain locust, the grasshopper 

 scourge of the West ; they attach themselves to the body under the 

 wings, and suck it to a dry shell; while still another species, T. seri- 

 ceum (Fig. 3), creep in great numbers into the holes where the locusts' 

 eggs are and. eat them. 



The Gamasidce are for the most part parasitic on insects, as the 

 beetle, bumblebee, wasp, etc., though the kinds here noticed are 

 found on warm-blooded animals. They are sometimes called ticks, 

 and are closely allied to that family. The mite shown in Fig. 4, 

 Dermanyssus aviicm, infests domestic poultry, canaries, and other 

 cage-birds, living in henneries and aviaries, and ready, like many of 

 its congeners, to migrate to persons the first opportunity. They are 

 small, w^hite, and quite agile. A case is related in which these mites 

 settled upon the skin of a woman otherwise healthy. She was con- 

 stantly infested with little, louse-like animals, w^hich were supposed 

 to be bred on her body, as the greatest cleanliness failed to extir- 

 pate them. It was at last found that she w^ent several times a day 

 into a cellar over which the hen-roost was located. As often as she 

 passed the fowls flew up to their roosts, and by this means sprinkled 

 the woman with mites. The removal of the hen-roosts cured her. 

 Fowls, when allowed to roost in stables, sometimes convey these mites 

 to horses, torturing the poor brutes nearly to death, the OAvner being 

 unable to decide what malady afflicts them. The mite is easiest ob- 



