GENUS NOTHRUS. 479 



Genus— NOTHRUS,* Koch. 



Equals pavt of Nothrus, Koch. 



Equals Liodes, and some other genus or genera, but it is not 



known which, Heyden. 

 Equals Nothrus, Nicolet, Canesti'ini, &c. 

 Equals Nothrus and Liodes, Berlese. 



ApterogasterincB with ceplialothorax anchylosed to 

 abdomen ; without lamellae. Abdomen square, oblong, 

 rhomboid, or shield-shaped. Notogaster flat or hollow, 

 or with a raised margin ; cuticle of adult usually 

 imperfectly chitinised. Abdomen not segmented. 



This genus was instituted by Koch, but he does not 

 define it clearly, and the creatures which he includes 

 in it are a very ill-assorted group ; it is scarcely pos- 

 sible to have much confidence as to what Koch's idea 

 really was ; the main strength of his genus, however, 

 is formed of what is now considered as the genus 

 Nothrus. Nicolet defined the genus much more clearly, 

 although he included one or two species which it is 

 necessary to exclude (as Hermamiia nanus) ; his reliance 

 on the claws as a basis of classification has broken 

 down, but in most other respects his views may be 

 considered correct ; he took for his type iV^. spiniger, 

 and in my opinion he could not have selected a better. 

 I have retained this species as my type. Berlese has 

 lately taken N. horridiis as a type; it would have 

 been a good type, but not better than N. spmiger, and 

 it is open to the objection that acarologists are not 

 agreed as to what is the true N. Iwrridus ; indeed, in 

 my opinion, Berlese' s horridus is not the original 

 species (of Hermann). 



Such species as N. spiniger and N. hoTridus are 

 forms quite distinct from every other genus, and there 

 are many other species quite of the type of these two ; 

 but these typical forms are joined by several inter- 



* NwOpof, sluggish. 



