DESCEIPTIONS OF GENERA AND SPECIES. 189 



I have endeavoured to give figures of the adult of 

 each species ; and it has usually been necessary to draw 

 both sexes, which was not requisite in the Oribatidse ; 

 but, on the other hand, I have not usually thought it 

 worth while to figure the larva or ordinary nymph, as 

 these would be easily recognised from the adult in 

 most cases ; but I have always drawn the Hypopus, 

 where one is known, as that is quite different. 



A description of each species is given, which I trust 

 may prove sufficient. A statement of the characters 

 of each genus is also added, and at the end of it a 

 table to assist in the identification of such British 

 species as are known to me ; these tables are not 

 intended as classifications but simply as aids to identi- 

 fication. There is not any record of what are 

 British species previous to this book ; it is scarcely 

 likely that I have found them all ; it is possible that 

 the discovery of further British species may render 

 some of these tables less exhaustive ; but at the end of 

 vol. 2 a short summary of the foreign species known 

 at present will be found. 



It must be remembered that in attributing species 

 to the earlier writers, and even to C. L. Koch, a doubt 

 must generally exist whether the species described are 

 really those of the authors referred to, whose descrip- 

 tions and figures, as a rule, do not admit of certainty. 



The figures of whole creatures are mostly to some 

 extent diagrammatic in position ; living Acari do not 

 usually assume the " spread-eagle " posture in which it 

 is convenient to draw them in order to display the 

 legs; in reality the tibiae and tarsi are usually held 

 perpendicularly, by which means the body of the 

 creature is usually kept off the ground; therefore, 

 when looking on the dorsal aspect the genual is often 

 the lowest joint seen ; but if they were drawn thus the 

 form of the leg would be lost, and it is often useful 

 for identification. 



The rostrum is often very mobile and can be raised 

 or depressed, and to some extent exerted or retracted. 



