Sub-order e. Astigmata.—Degenerate, mostly parasitic forms approaching the Prostigmata in the development of integumental sclerites and the softness of the skin, but with the respiratory system absent.
Families—Tyroglyphidae (Tyroglyphus, Rhizoglyphus).
Sarcoptidae (Sarcoptes, Analges).
Sub-order f. Vermiformia.—Degenerate atracheate parasitic forms with the body produced posteriorly into an annulated caudal prolongation, and the 3rd, 4th, 5th and 6th pairs of appendages short and only three-jointed.
Family—Demodicidae (Demodex).
Sub-order g. Tetrapoda.—Degenerate atracheate gall-mites in which the body is produced posteriorly and annulated, as in Demodex, but in which the appendages of the 3rd and 4th pairs are long and normally segmented and those of the 5th and 6th pairs entirely absent.
Family—Eriophyidae (Eriophyes, Phyllocoptes).
Remarks on the Rhynchostomi.—The Acari include a number of forms which are of importance and special interest on account of their parasitic habits. The ticks (Ixodes) are not only injurious as blood-suckers, but are now credited with carrying the germs of Texas cattle-fever, just as mosquitoes carry those of malaria. The itch-insect (Sarcoptes scabiei) is a well-known human parasite, so minute that it was not discovered until the end of the 18th century, and “the itch” was treated medicinally as a rash. The female burrows in the epidermis much as the female trap-door spider burrows in turf in order to make a nest in which to rear her young. 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. A species of Acarus is recorded as infesting a store of powdered strychnine and feeding on that drug, so poisonous to larger organisms. Reference to literature (40).
Authorities cited by numbers in the text.—1. Strauss-Dürckheim (as reported by MM. Riester and Sanson in an appendix to the sixth volume of the French translation of Meckel’s Anatomy, 1829); 2. Lankester, “Limulus an Arachnid,” Quart. Journ. Micr. Sci. vol. xxi. N.S., 1881; 3. Idem, “On the Skeletotrophic Tissues of Limulus, Scorpio and Mygale,” Quart. Journ. Micr. Sci. vol. xxiv. N.S., 1884; 4. Idem. Trans. Zool. Soc. vol. xi., 1883; 5. Lankester and A.G. Bourne, “Eyes of Limulus and Scorpio,” Quart. Journ. Micr. Sci. vol. xxiii. N.S., Jan. 1883; 6. Milne-Edwards, A., “Recherches sur l’anatomie des Limules,” Ann. Sci. Nat. 5th Series, Zoologie, vol. xvii., 1873; 7. Owen, Richard, “Anatomy of the King-Crab,” Trans. Linn. Soc. Lond., vol. xxviii., 1872; 8. Kishinouye, “Development of Limulus longispina,” Journal of the Science College of Japan, vol. v., 1892; 9. Brauer, “Development of Scorpion,” Zeitschrift für wiss. Zoologie, vol. lix., 1895; 10. Hansen, H.J., “Organs and Characters in Different Orders of Arachnida,” Entomol. Meddel. vol. iv. pp. 137-149; 11. Watase, “On the Morphology of the Compound Eyes of Arthropods,” Studies from the Biolog. Lab. Johns Hopkins University, vol. iv. pp 287-334; 12. Newport, George, “Nervous and Circulatory Systems in Myriapoda and Macrourous Arachnids,” Phil. Trans. Roy. Soc., 1843; 13. Lankester, “Coxal Glands of Limulus, Scorpio and Mygale,” Quart. Journ. Micr. Sci. vol. xxiv. N.S., 1884; 13A. W. Patten and A.P. Hazen, “Development of the Coxal Glands of Limulus,” Journ. of Morphology, vol. xvi., 1900; 13B. Bernard, “Coxal Glands of Scorpio,” Ann. and Mag. Nat. Hist. vol. xii., 1893, p. 55; 14. Benham, “Testis of Limulus,” Trans. Linn. Soc., 1882; 15. Lankester, “Mobility of the Spermatozoa of Limulus,” Quart. Journ. Micr. Sci. vol. xviii. N.S., 1878; 16. Korschelt and Heider, Entwickelungsgeschichte (Jena, 1892), ibique citata; 17. Laurie, M., “The Embryology of a Scorpion,” Quart. Journ. Micr. Sci. vol. xxxi. N.S., 1890, and “On Development of Scorpio fulvipes,” ibid. vol. xxxii., 1891; 18. Lankester (Homoplasy and Homogeny), “On the Use of the term Homology in Modern Zoology,” Ann. and Mag. Nat. Hist., 1870; 19. Idem, “Degeneration, a Chapter in Darwinism,” 1878, reprinted in the Advancement of Science (Macmillan, 1890); 20. Idem, “Limulus an Arachnid,” Q. J. Micr. Sci. vol. xxi. N.S.; 21. Claus, “Degeneration of the Acari and Classification of Arthropoda,” Anzeiger d. k. k. Akad. Wissen. Wien, 1885; see also Ann. and Mag. Nat. Hist. (5) vol. xvii., 1886, p. 364, and vol. xix. p. 225; 22. Lindstrom, G., “Researches on the Visual Organs of the Trilobites,” K. Svenska Vet. Akad. Handl. xxxiv. No. 8, pp. 1-86, Pls. i.-vi., 1901; 22*. Zittel, American edition of his Palaeontology (the Macmillan Co., New York), where ample references to the literature of Trilobitae and Eurypteridae will be found; also references to literature of fossil Scorpions and Spiders; 23. Hoek, “Report on the Pycnogonida,” Challenger Expedition Reports, 1881; Meinert, “Pycnogonida of the Danish Ingolf Expedition,” vol. iii., 1899; Morgan, “Embryology and Phylogeny of the Pycnogonids,” Biol. Lab. Baltimore, vol. v., 1891; 24. Bourne, A.G., “The Reputed Suicide of the Scorpion,” Proc. Roy. Soc. vol. xlii. pp. 17-22; 25. Lankester, “Notes on some Habits of Scorpions,” Journ. Linn. Soc. Zool. vol. xvi. p. 455, 1882; 26. Huxley, “Pharynx of Scorpion,” Quart. Journ. Micr. Sci. vol. viii. (old series), 1860, p. 250; 27. Pocock, “How and Why Scorpions hiss,” Natural Science, vol. ix., 1896; cf. idem, “Stridulating Organs of Spiders,” Ann. and Mag. Nat. Hist. (6), xvi. pp. 230-233; 28. Kraepelin, Das Thierreich (Scorpiones et Pedipalpi) (Berlin, 1899); Peters, “Eine neue Eintheilung der Skorpione,” Man. Akad. Wiss. Berlin, 1861; Pocock, “Classification of Scorpions,” Ann. and Mag. Nat. Hist. (6) xii., 1893; Thorell and Lindstrom, “On a Silurian Scorpion,” Kongl. Svens. Vet. Akad. Handl. xxi. No. 9, 1885; 29. Cambridge, O.P., “A New Family (Tartarides) and Genus of Thelyphonidea,” Ann. and Mag. Nat. Hist. (4) x., 1872, p. 413; Cook, “Hubbardia, a New Genus of Pedipalpi,” Proc. Entom. Soc. Washington, vol. iv., 1899; Thorell, “Tartarides, &c.” Ann. Mus. Genova, vol. xxvii., 1889; 30. M Cook, American Spiders and their Spinning Work (3 vols.; Philadelphia, 1889-1893); 31. Peckham, “On Sexual Selection in Spiders,” Occasional Papers Nat. Hist. Soc. Wisconsin, vol. i. pp. 1-113, 1889; 32. Moggridge, Harvesting Ants and Trap-Door Spiders (1873); 33. Bertkau, Ph., Arch. f. Naturgesch. vol. xlviii. pp. 316-362; Idem, same journal, 1875, p. 235, and 1878, p. 351; Cambridge, O.P., “Araneidea” in Biologia Centr. Americana, vols. i. and ii. (London, 1899); Keyserling, Spinnen Amerikas (Nuremberg, 1880-1892); Pocock, “Liphistius and the Classification of Spiders,” Ann. and Mag. Nat. Hist. (6) x., 1892; Simon, Hist. nat. des Araignées, vols. i. and ii., 1892, 1897; Wagner, “L’Industrie des Araneína,” Mem. Acad. St-Pétersbourg; Idem, “La Mue des Araignées,” Ann. Sci. Nat. vol. vi.; 34. Grassi, G.B. “Intorno ad un nuovo Aracnide artrogastro (Koenenia mirabilis) &c.” Boll. Soc. Ent. Ital. vol. xviii., 1886; 35. H.J. Hansen and Sörensen, “The Order Palpigradi, Thorell (Koenenia), and its Relationships with other Arachnida,” Ent. Tidskr. vol. xviii. pp. 233-240, 1898; Kraepelin, Das Thierreich (Berlin, 1901); 36. Bernard. “Compar. Morphol. of the Galeodidae,” Trans. Linn. Soc. Zool. vol. vi., 1896, ibique citata; Dufour, “Galeodes,” Mém. prés. Acad. Sci. Paris, vol. xvii., 1862; Kraepelin, Das Thierreich (Berlin, 1901); Pocock, “Taxonomy of Solifugae,” Ann. and Mag. Nat. Hist. vol. xx.; 37. Balzan, “Voyage au Vénézuela (Pseudoscorpiones),” Ann. Soc. Entom. France, 1891, pp. 497-522; 38. Guérin-Méneville, Rev. Zool., 1838, p. II; Karsch, “Ueber Cryptostemma Guer.” Berliner entom. Zeitschrift, xxxviii. pp. 25-32, 1892; Thorell, “On an apparently new Arachnid belonging to the family Cryptostemmidae,” Westv. Bihang Svenska Vet. Akad. Handligar, vol. xvii. No. 9, 1892; 39. Hansen and Sorensen, On Two Orders of Arachnida (Cambridge, 1904); Sörensen, “Opiliones laniatores,” Nat. Tidskr. (3) vol. xiv., 1884; Thorell, “Opilioni,” Ann. Mus. Genova, vol. viii., 1876; 40. Berlese, “Acari, &c., in Italia reperta” (Padova, 1892); Canestrini, Acarofauna Italiana (Padova, 1885); Canestrini and Kramer, “Demodicidae and Sarcoptidae” in Das Thierreich (Berlin, 1899); Michael, “British Oribatidae,” Ray Soc.; Idem, “Oribatidae” in Das Thierreich (Berlin, 1898); Idem, “Progress and Present State of Knowledge of Acari,” Journ. Roy. Micr. Soc., 1894; Nalepa, “Phytoptidae,” Das Thierreich (Berlin, 1898); Trouessart, “Classification des Acariens,” Rev. Sci. Nat. de l’ouest. p. 289, 1892; Wagner, Embryonal Entwick, von Ixodes (St Petersburg, 1803); 41. Bertkau, Ph., “Coxaldrusen der Arachniden,” Sitzb. Niederl. Gesellsch., 1885; 42. Patten, W., “Brain and Sense Organs of Limulus,” Quart. Journ. Mic. Sci. vol. xxxv., 1894; see also his “Origin of Vertebrates from Arachnids,” ibid. vol. xxxi.
Authorities not cited by numbers in the text:—