166 BRITISH TYROGLYPHIDJ;. 



against the rough plate at the upper side of the furrow ; 

 thus the hair is firmly held between the two. 



There are but fe"w species known to have homopial 

 Hypopi; for these it may possibly, some day, be 

 desirable to revive Haller's genus Dermacarus ; but the 

 propriety of this cannot be judged of until it is ascer- 

 tained with certainty whether some closely allied 

 species possess a hypopial stage or not, and if they do 

 whether it is homopial. The Hypopus of the first of 

 these species was described by C. L. Koch in 1841 

 under the name of Dermaleiclius sciurinus,* and in 1842 

 under that of Homopus sciurinus ; t it is figured in this 

 book (PL XVIII, figs. 5, 6 ; PL XIX, figs. 1518). 

 In 1844 Koch J described what was probably the 

 homopial Hypopus of another species under the name 

 of Homopus liypuddBi ; it was found on the field-mouse 

 Hypuddeus arvalis. It is not possible to be quite certain 

 of its hypopial nature from Koch's figure and descrip- 

 tion. In 1849 Dujardin described under the name of 

 Hypopus arwcolae a creature which was probably 

 identical with Koch's Homopus hypudsei. In 1877 

 Kramer found upon the mole, and described || under 

 the name of Labidophorus talpce, a creature which is 

 the homopial hypopus of Glycyphagus Cramer i, and is 

 figured in this book (PL XVI, fig. 5). Dr. Oudemans If 

 considers that he has obtained the homopial Hypopi of 

 several other species on rats and mice, but he does not 

 name, figure, or describe them. 



Of the Trichotarsus type of Hypopi only a very few 

 species (four, I believe) are known. It is not quite 

 certain that they are Hypopi at all ; they are certainly 

 immature. This was proved by Prof. Berlese, and I 

 have subsequently been able to verify his correctness 

 in this respect; although at one time, before he called 



* Koch, D. C., fasc. 33, No, 7. 



t Koch, Uebersi, Heft 3, p. 121. 



J Koch, D. C., fasc. 39, No. 24. 



| In ' Ann. Sci. Nat,,' 3e ser., t. xii, p. 264, pi. ii, figs. 15, 16. 



|| In ' Arch. Naturg.,' vol. xliii, Heft 1, pp. 249259. 



j[ Oudemans' list, pp. 252, 253. 



