Acari

“ The Ligulæ of the Cyprinidæ, found in the intestines of the cormorant or the goosander, are not, in our opinion at least, worms peculiar to these birds. They are strangers which must either emigrate again or die. Acari which originally belonged to mammals and birds, have been found living on man, causing prurigo, or even serious maladies, and yet these parasites are not regarded as peculiar to our species. ”

“ Parasite: Dermanyssus gallinæ, or chicken acari. Malady: Poultry acariasis.—This is a large-sized acarus, though usually miscalled "hen louse," and the disease "poultry lousiness." The mite (Pl. XXXIX, fig. 4) lives in droppings and in crevices of chicken houses, but temporarily passes on to the skin of man and of the horse and other quadrupeds, when occasion serves. It causes much irritation, with the eruption of papules or vesicles and the formation of sores and scabs. ”

“ Like other acari, this is wonderfully prolific, a new generation of fifteen individuals being possible every fifteen days, so that in three months the offspring of a single pair may produce generations aggregating 1,500,000 young. The Sarcoptes have less vitality than the nonburrowing acari, as they die in an hour when kept apart from the skin in dry air at a heat of 145° F. They live 12 to 14 days apart from the skin in the damp air of a stable. ”

“ She keeps watch; she brushes off the parasitic growths; she closes up the cracks; she drives off any ravagers that may appear: Acari,1 tiny Staphylini,2 grubs of small Flies, Aphodii,3 Onthophagi.4 In September she climbs to the surface with her family, which, having no further use for her, emancipates itself and henceforth lives as it pleases. ”

“ The male acari, when placed on the sound skin of a sheep, will likewise burrow their way and [237] disappear for a while, the pustule rising in due time; but the itching and the scab soon disappear without the employment of any remedy. The female brings forth from eight to fifteen young at a time.
In the United States, this disease is comparatively little known, and never originates spontaneously. The fact, that short-woolled sheep—like the Merino—are much less subject to its attacks, is probably one reason for this slight comparative prevalence. ”

“ A hundred years ago, naturalists, and especially other men, might easily have been made to believe that many of the smaller insects had a casual origin. But long since, save in the matter of the acari, the entomological field has been abandoned by the advocates of the law hypothesis, and they have been driven from one tribe after another, till at length some of the obscure hiding-places of the entozoa and infusoria are now the only spots where the light is not too strong for the large-pupiled eyes of this hypothesis. ”

“ THE acari constitute a large order of minute animals, including mites, ticks, itch insects, etc, with which, in some of their forms, every one is more or less familiar, though, owing to their small size and obscure ways of living, but little is known of their structure and habits. ”

“ The families are Oribatidae, Argasidae, Ixodidae, and Gamasidae.
Fam. 1. Oribatidae.—The Oribatidae or “Beetle-mites” are free-living Acari, with tracheae of which the stigmata are concealed by the articulation of the legs. The cephalothorax is distinctly marked off from the abdomen, and bears dorsally two “pseudo-stigmatic” organs. The rostrum is inserted below the cephalothorax. These Mites gain their popular name from the beetle-like hardness of their integuments. They are oviparous or ovoviviparous. Eyes are always absent. ”

“ It is not so much a parasite as an assassin, and we may be excused from describing it. We have found acaridæ on certain polyps, the Campanulariæ and Sertulariæ of our coasts, and some years ago we described one which is very curious, and inhabits the southern whale, in the midst of its Cyami and Tubicinellæ. The anodonts of our ponds, as well as the Uniones usually have the skin of their feet and that of their mantle encrusted with acari of every age, to which the name of Atax ypsilophora has been given. The species which live on the anodonts are not the same as those which inhabit the Uniones ”

“ The crusts steadily grow thicker and lift the individual fibres of wool, tearing them from their follicles, so that patches of skin become bare. The patches thus formed increase in diameter, for the acari leave the centre, where crust-formation is replaced by abundant desquamation of the epidermis. The skin is thickened, assumes the character of parchment, and in old-standing cases becomes wrinkled. ”

“ There is no doubt, from a consideration of the facts of structure, that the aquatic water-breathing Arachnids, represented in the past by the Eurypterines and to-day by the sole survivor Limulus, have preceded the terrestrial air-breathing forms of that group. Hence we see at once that the better-known Arachnida form a series, leading from Limulus-like aquatic creatures through scorpions, spiders and harvest-men, to the degenerate Acari or mites. ”

“ An animal badly nursed will not, under the most skillful treatment, quickly recover. Its causes are in the main, due to poor food, which produces a debilitated condition of the system, and in connection with a want of cleanliness, causes a development of the acari, or minute insects, exciting very great irritation upon the skin and causing the cow to rub herself against every object with which she comes in contact. The hair falls off; a scurfy appearance of the skin is perceptible; and the animal is poor in condition and in milk. ”

“ It may be detected by dissolving two or three spoonfuls of sugar in warm water, and allowing the solution to stand for an hour or so; at the end of the time the acari will be found floating on the surface, adhering to the sides of the glass, and lying mixed with the grit and. dirt that always accumulate at the bottom. In ten grains of sugar as many as 500 mites have been found, which is at the rate of 350,000 to the pound. Those who are engaged in handling raw sugars are subject to an eruption known as "grocers' itch," which is doubtless to be traced to the presence of these mites. ”

“ The disease spreads from individual to individual, and from flock to flock, not only by means of direct contact, but by the acari left on posts, stones, and other substances against which diseased sheep have rubbed themselves. Healthy sheep are, therefore, liable to contract the malady, if turned on pastures previously occupied by scabby sheep, although some considerable time may have elapsed since the departure of the latter. ”

“ ARACHNIDA EMBOLOBRANCHIATA (CONTINUED) —ACARINA—HARVEST-BUGS—PARASITIC MITES—TICKS—SPINNING MITES—STRUCTURE—METAMORPHOSIS—CLASSIFICATION Order IX. Acarina (Acari, Acaridea) . Arachnids with unsegmented, [349] non-pediculated abdomen. Respiration by tracheae, or by the general surface of the body. Month parts suctorial, but frequently capable of biting or piercing. Metamorphosis always observable. ”

“ The sexes are not distinct, the sexual organs being represented by a pair of testes and a single ovary, which open together into the posterior end of the alimentary canal. The Tardigrada have been regarded as degenerate Acari largely on account of their possessing four pairs of ambulatory limbs, which is considered to be an Arachnidan characteristic. ”

“ They do not seem to be present in all persons, occurring in two or three cases out of ten, and seeming to prefer thick, greasy skins. They are entirely harmless, and their presence is no indication of disease. The family roll of the acari closes with the gall-mites, Phytoptidæ, a curious and little-known group that causes the abnormal growths known as galls on the leaves and other parts of various plants. ”

“ Some of the commoner forms of naturally acquired infection may be briefly mentioned, without however touching upon the various fleas, lice and ticks which at times infect the ordinary laboratory animals.
Fig. 165.—Back of inoculation card.
The Rabbit, particularly in captivity, is subject to [Pg 338] attacks of Psoric Acari, and the infection is readily transmitted to rabbits in neighbouring cages and also to guinea pigs, but not to rats and mice. One species (Sarcoptes minor var. cuniculi) gives rise to the ordinary mange. ”

“ Experiments have been brought forward, in which it appeared that, after all organization which could by any possibility have existed, had been destroyed by the action of fire, solutions of flint and metallic salts, have, under the influence of electric currents, exhibited signs of organic formations, and that, indeed, insects—a species of acari—have been developed in them. ”

“ This concentration and obliteration of somites, often accompanied by dislocation of important segmental structures (such as appendages and nerve-ganglia) , may lead to highly developed specialization (individuation, H. Spencer) , as in the Araneae and Opiliones, and, on the other hand, may terminate in simplification and degeneration, as in the Acari.}
The most important general change which has affected the structure of the nomomeristic Arachnida in the course of their historic development is the transition from an aquatic to a terrestrial life. ”

“ A slight immunity from the attacks of acari and pediculi might in a tropical country more than compensate an animal for the loss of its hairy coat, especially in the case of the domesticated dog, which finds shelter with its master, has not to seek for its food at night, and is protected from the attacks of stronger animals. ”

“ A creature is also found in wax long laid by, just as in wood, and it is the smallest of animalcules and is white in colour, and is designated the acari or mite. In books also other animalcules are found, some resembling the grubs found in garments, and some resembling tailless scorpions, but very small. As a general rule we may state that such animalcules are found in practically anything, both in dry things that are becoming moist and in moist things that are drying, provided they contain the conditions of life. ”

“ Crosse's electrical Acari, which were developed de novo, out of inorganic material, in a dirty galvanic battery, and yet possessed all the limbs and organs of degenerate spiders. It is asking us once more to accept a still greater miracle than the first. ”

“ The mange which is received by contagion is more readily given to another than that which is generated. The uniform presence of animalculi within the psoric pustules has revived the idea that it originates in the attack of acari. ”

“ The male does not burrow, but wanders freely on the surface of the skin. Demodex folliculorum is also a common parasite of the sebaceous glands of the skin of the face in man, and is frequent in the skin of the dog. Many Acari are parasitic on marine and freshwater molluscs, and others are found on the feathers of birds and the hair of mammals. Others have a special faculty of consuming dry, powdery vegetable and animal refuse, and are liable to multiply in manufactured products of this nature, such as mouldy cheese. ”

“ The rate at which these Acari breed is very great. Gerlach has found that roughly, in each Sarcopt gallery, a female produces fifteen individuals—ten females and five males—and that the progeny reproduce again in fifteen days. ”

“ We call those diseases "parasitic" that are occasioned by the introduction of a living organism into the bodies of animals. Although a knowledge of such diseases is easy where it concerns parasites such as acari and worms, it becomes very difficult when it is a question of diseases that are caused by the Bacteriaceæ. ”

“ The wild bees’ parasites are of two kinds, personal, and such which, like the young of cuckoos, live at the expense of the offspring. The personal parasites are again of two kinds, for bees are infested with several kinds of Acari, and once I found a Bombus upon the ground in Coombe Wood so swarming with the Acarus that it lay hopelessly helpless until I threw it into a pool of water, when its attachés were washed away. ”

“ Thus we may assume that no animal is free in this respect, and man himself regularly affords hospitality to many of them. We feed some with our blood and our flesh; there are some which lodge on the surface of our skin, others in the interior of our organs; some prefer to establish themselves on children, others on adults. The name alone of some is sufficient to make us shudder, while others live peaceably in some crypt, without our suspecting their presence. Who is there that does not nourish some acari, of the genus Simonea, in the membrane of the nose? ”

“ The concealment of these tiny creatures during daylight renders it difficult to watch their proceedings, or to discriminate the precise species most actively engaged; but there is every reason to believe that the larvæ of the death-watch and numerous acari are amongst the most active. As nature seldom peoples a region supplied with abundance of suitable food, without, at the same time, taking measures of precaution against the disproportionate increase of individuals; so have these vegetable depredators been provided with foes who pursue and feed greedily upon them. ”

“ Ewing also showed that among the living forms of Acarina we can trace out all the stages of advancing parasitism, semiparasitism, facultative parasitism, even to the fixed and permanent type, and finally to endoparasitism.
Of the many parasitic forms, there are several species which are serious parasites of man and we shall consider the more important of these. Infestation by mites is technically known as acariasis. ”

“ It has just been discovered that a most remarkable symbiosis, with structural modification of the bee, exists between the females of Xylocopa, of the Oriental sub-genus Koptorthosoma, and certain Acarids. A special chamber, with a small orifice for entry, exists in the abdomen of the bee, and in this the Acari are lodged.—See Perkins, Ent. ”