British Oribatidse. Bjf A. D. Michael 229 



confessed that the descriptions and figures are often scarcely suffi- 

 cient for identification, and that every specimen which presents the 

 smallest difference is given as a distinct species ; often the male, 

 female, and nymph, and even the nymph after each change of skin, 

 are given as distinct species, producing confusion. Koch had 

 scarcely a genius for classification ; his genus Nothrus for instance 

 is a strange collection of heterogeneous creatures. I should think 

 it my fault that several of his genera do not convey any clear idea 

 to my mind, if such men as Nicolet, Mui'ray, and Megnin, had not 

 said the same thing before me. 



Hermann* has described and figured several species in a 

 manner, like all his work, most admirable, considering the date, but 

 not always sufficient for modern requirements. 



Duges, t in his excellent papers on the Acarina, treats of the 

 Oribatidge, but more shortly than of the other families. 



Ed. Claparede t gives some highly interesting observations of 

 the transformations of Hoplo-pliora, &c. 



There are numerous other authors, such as Gervais,§ De 

 Geer, || Latreille, 1[ Lucas,** Thorell,tt &c., whose works contain 

 valuable information. 



General Olservations. 



It appears to be the result of modern research that the 

 Orihatldai are the only family of Acarina no species of which is 

 ever parasitic at any stage of its existence ; the various Sarcoptidfe 

 and some others of the true Acari are always parasitic, the 

 Ixodidw partly so ; the Gamasinse and many of the Hydrachnidai 

 are parasitic during the nymph stage ; the Tromhididm during the 

 curious hypopial nymph stage ; XX and ]\legnin has lately shown 

 that even some of the Cheyleti are in a sense parasitic, §§ but 

 it never occurs amongst the Orihatidw. 



It seems to me that the numerous contrivances for protecting 

 the legs in the Oribatidse have not been sufficiently noticed, nor 

 their purpose understood ; the animals are all vegetable feeders, and 

 are slow and cannot escape from enemies by running ; they are not 

 provided with weapons of defence, but are furnished with a very 

 hard shell, and their safety consists in trusting to it and " shamming 

 dead " : this would be useless if their legs were exposed. Everyone 

 who has seen a predatory mite seize a victim, knows that it usually 



* ' Me'moire Apterologiqiie,' Strasbourg, 1804. 



t ' Annales des Sciences Natiu-elles,' lS3-i. 



X ' Studien iiber die Acariden,' Leipzig, 1868. 



§ 'Histoire Nat. des Apteres,' Paris, 1847. 



II 'Me'moires pour servir a I'Hist. Nat. des Insectes,' Stockholm, 1778. 



^ ' Hist. Nat. des Crustaces et des Insectes,' Paris, An XII. 



** ' Exploration Scientifique de I'Alge'rie.' 



tt ' Oefv. Sv. Ak.,' 28, 695. (1871.) 



XX Megnin, 'Journal de rAuatomie,' 1874. 



§§ Ibid., 1878. 



