LIST OF ILLUSTRATIONS FIG. I. Demodex canis (after Megnin) 2. Demodex equi 3. Sarcoptes suis-Ovum 4. Sarcoptes suis-Ovum 8. Sarcoptes suis-Female 9. Sarcoptes equi-Sucker and pedicle 10. Sarcoptes equi-Male, female, and egg (after Newstead and Morris) II. Notædres cati-Male 12. Notædres cati-Female 13. Cnemidocoptes mutans-Female 14. Cnemidocoptes mutans-Larva 15. Cnemidocoptes gallina-Male and female (after Railliet) 16. Psoroptes equi-Male 18. Psoroptes equi-Male and female in copula 17. Psoroptes equi-Ovigerous female 19. Psoroptes equi-Pubescent female 20. Psoroptes equi-Sucker and pedicle 21. Psoroptes equi-Male, female, and egg (after Newstead and Morris) 22. Chorioptes equi-Male 24. Chorioptes equi-Male 23. Chorioptes equi-Ovigerous female 25. Chorioptes equi—Male, female, and egg (after Newstead 29. Cytoleichus nudus-Female (after Railliet) 30. Cytoleichus nudus-Female 31. Laminosioptes cysticola-Male and female (after Railliet) 32. Aleurobius farina-Male 33. Aleurobius farinæ-Female 34. Aleurobius farinæ—Larva (after Newstead and Duvall) xi FIG. 35. Aleurobius farinæ-Damaged specimen 40. Tyroglyphus longior—Hypopus (after Michael) 42. Hypopial Nymph 43. Tyroglyphus longior-Ovum (after Michael) 44. Tyroglyphus siro-Male and female (after Michael) 45. Glyciphagus domesticus-Female PAGE 70 71 71 72 72 73 73 73 74 75 78 46. Glyciphagus domesticus-Female (after Michael) 47. Glyciphagus domesticus—Male (after Michael) 48. Glyciphagus domesticus-Hypopus (after Michael) 49. Glyciphagus cadaverum-Female and egg (after Newstead and Morris) 50. Glyciphagus cadaverum-Female 80 81 51. Glyciphagus ornatus—Male (after Newstead and Morris) 52. Listrophorus gibbus-Male 53. Listrophorus gibbus-Female 85 54. Tydeus molestus―(after Moniez) 87 55. Pediculoides ventricosus-Male and female (Castellani and Chalmers) 56. Tarsonemus latus—Male and female (after Banks) 57. Cheyletus eruditus 58. Cheyletus eruditus—Female (after Newstead and Morris) 59. Cheyletiella parasitivorax (Neumann) MANGE AND ALLIED MITES CHAPTER I INTRODUCTION THE ECONOMIC IMPORTANCE OF DISEASE- ACARI are responsible for a great amount of disease amongst the lower animals. The conditions produced by them are spoken of as itch, scab, mange, scabies, and a number of local names. Some of them have been recognised from biblical times. The three forms of equine scabies give rise to serious annual loss. Two of them, psoroptic and sarcoptic, are subject to the Parasitic Mange Orders. In the United Kingdom during 1919 there were 5,003 outbreaks with 9,773 horses attacked. If all these animals recovered after a course of treatment lasting twenty-one working days, and the loss per day be estimated at ten shillings, this would represent £102,616 per annum. As a matter of fact a large number of animals are destroyed, and many are more than twenty-one days under treatment. Whenever large numbers of animals are collected together mange is apt to appear, and it becomes aggravated if conditions of housing and management are unsatisfactory. This was the experience in the Crimean, Franco-Prussian, and South African Wars. When the veterinary history of the late war comes to be written, scabies will occupy one of the most important places. It must have cost the nation immense sums for treat ment alone, yet it was well controlled when compared with previous campaigns. In bovines mange is not quite so important, yet the sarcoptic form is one of the commonest skin diseases of housed animals. Sheep scab is subject to a number of official Orders; it occurred in sixty-two counties of the United Kingdom during 1919, and there were 438 outbreaks. In some countries rigid measures have exterminated this disease. Among swine, sarcoptic scabies is far from rare. In canine practice skin lesions and otorrhoea, of parasitic origin, occupy an importance which cannot be exaggerated an account of the proximity of canine pets to their owners. The cat, too, is not exempt from both skin and auditory lesions due to acari. Many of the domestic birds are liable to the attacks of mites. At times outbreaks of scabies amongst the laboratory animals have led to serious inconveniences, especially in the case of rabbits and small mammals. A number of wild animals suffer from mange, and ferret breeding has at times been menaced by it. Menageries, zoological collections, and travelling shows of wild exotic carnivora and ruminants, are sometimes seriously attacked by scabies. The manufacture of parasiticides for the treatment and prevention of diseases caused by acari forms a large part of the work of some chemical companies. A considerable part of the time of veterinarians and others both at home and abroad is devoted to the control of the ravages produced by mites. Additional importance is added to scabies by the fact that in quite a number of cases the disease upon animals is communicable to man. THE DISTRIBUTION OF MITES IN NATURE Coming into close touch, as he usually does, with two or three genera of mites, the veterinarian is inclined to become a little cramped in his views with regard to this group, and to exhibit surprise when something not conforming with his mental picture is encountered upon a slide. A great number of mites are marine or aquatic, and others are found upon grasses, plants, shrubs, and trees, where they may or may not produce disease. Some are found upon dried crops, such as hay, straw, grain, and farinaceous materials, and many of these are brought into the closest contact with the domesticated animals either in transport, or as bedding and feeding materials. Certain genera prefer sugar-containing fruits, such as figs and dates; whilst others choose decaying vegetable substances. The soft fur of some species of mammals is the happy hunting-ground of some mites which do not appear to produce any inconvenience; and these are likely to be encountered when material from the skin of such an animal is subjected to microscopic examination for suspected scabies. A very large group of mites are found in the feathers of birds; a number of these rarely cause inconvenience, yet they may be confused in diagnosis with pathogenic ones, or even get upon animals when birds or their nests are near buildings in which animals are housed. As unusual habitats, the following examples are noteworthy: Certain species of Halarachne are found in the bronchial passages of seals, and Pneumonyssus sp. occur in the lungs of some monkeys. Numerous members of the chief groups of the Insecta are liable to have mites upon them. Histiostoma berghi lives parasitically in the egg-capsules of leeches in Denmark. |