LEPTUS.—Two species of leptus are met with as attacking man: Leptus Americanus (American harvest mite) and Leptus irritans (irritating harvest mite, harvest bug, mower's mite). The former is a minute, brick-red colored, elongate, pyriform creature with six legs, barely visible to the naked eye. Its favorite sites of attack are the scalp and axillæ, partly burying itself in the skin, giving rise to a small inflammatory papule. The latter species is more common, differing from the former merely in having a roundish oval form. It buries itself in the skin, giving rise to inflammatory papules, vesicles, and pustules. Its sites of predilection are the ankles and legs. The minute red mite met with especially about blackberry-bushes in the low grounds of Pennsylvania, New Jersey, and Delaware is probably the same species. Both varieties are common, during the summer, in our South-western States. For treatment a weak sulphur ointment or ointments of the other mild parasiticides may be employed.
PULEX PENETRANS, OR RHINOCHOPRION PENETRANS.—This creature—the sand-flea, known also as chigoe, chigger, and jigger—is almost microscopic in size, closely similar to the common flea, but has a proboscis as long as its body. It is common in tropical countries, and also met with in our Southern States. It (the impregnated female) burrows into the skin, depositing the ova, resulting in inflammatory swelling, large vesicles or pustules, and even ulceration. The toes, especially beneath and alongside of the nail, and other parts of the feet are the regions attacked. The treatment consists in extraction; it usually comes away in the form of a sac about the size of a small pea, its size due to the distension of the abdomen with ova. As a preventive the essential oils are used about the feet.
FILARIA MEDINENSIS.—This parasite, the guinea-worm, known also as dracunculus, is only encountered in tropical countries. The young bore into the skin and subcutaneous tissue, in which their growth takes place; sooner or later marked inflammation is produced, resulting in painful furuncular tumors, which finally break, showing the presence of the worms. The lower extremities, especially the feet, are the favorite regions of attack. The worm varies from several inches to three feet in length, according to its age, and is one-half or three-fourths of a line in thickness. The treatment consists in extracting the worm inch by inch, from day to day, as soon as discovered, care being exercised not to break it. Poultices may be applied.
CYSTICERCUS CELLULOSÆ.—This affection is characterized by rounded or ovalish, smooth, elastic, firm or hard, movable, pea- to hazelnut-sized tumors, more or less numerous, usually seated just beneath the skin, new tumors showing themselves from time to time. After reaching a certain size they may remain stationary. Although not painful upon pressure, spontaneous pains may be complained of. Microscopical examination reveals the cysticerci.
OESTRUS.—This parasite (known also as breeze, gad-fly, and bot-fly) is met with in Central and South America, and also in other countries. The neck, back, and extremities especially are liable to be attacked. The ova are deposited in the skin, and there result inflammatory, boil-like tumors or swellings with a central opening, from which issues a sanious fluid; or the lesion may assume a linear, tortuous, or serpiginous form. Sooner or later the grub is detected, and may be easily squeezed out or extracted.
DEMODEX FOLLICULORUM.—This microscopic parasite (also known as steatozoon, entozoon, acarus, and Simonea, folliculorum) is to be found in the sebaceous follicles. It is harmless, giving rise to no disturbance. It is worm-like in form, made up of a head, thorax, and a long abdomen. It is more apt to be found in those with thick, greasy skins. Several of them often exist in a single follicle.
CIMEX LECTULARIUS, OR ACANTHIA LECTULARIA.—This insect (the common bed-bug) and its various residing-places are well known. It gives rise to a cutaneous lesion of the nature of an urticarial wheal, with a central hemorrhagic point which remains after the swelling has subsided. As a result of the scratching to which the irritation and itching give rise excoriations are often observed. A larger species (Conorhinus sauguisuga), known as the blood-sucking cone-nose and big bed-bug, has been met with in Southern Illinois and Ohio; its bite is said to produce severe inflammation of the skin. For the relief of bed-bug bites lotions containing alcohol, vinegar, lead-water, ammonia-water, and similar remedies may be sponged upon the parts. Pyrethrum powder and corrosive sublimate are the best preventives against bugs in beds.
PULEX IRRITANS.—This, the common flea, is found universally, especially in hot and warm climates. As a result of its bite erythematous spots with minute central hemorrhagic points are seen. The presence of the areola distinguishes the lesions from those of simple purpura, which at times they may resemble. The cutaneous disturbance is usually slight, but in some individuals, and especially in tropical countries, the discomfort to which these creatures give rise is often considerable.
CULEX.—Gnats, or mosquitoes, are often productive of considerable cutaneous irritation, the typical lesion being a wheal-like elevation. The itching is best relieved with ammonia-water.
IXODES.—There are several species of wood-ticks met with in our woods which are liable to attach themselves to the human skin. Inserting their proboscis and head deeply into the tissues, they suck blood until often they swell up several times their natural size. They should be induced to relinquish their firm hold by dropping olive oil or one of the essential oils upon the skin; they should never be extracted with violence.