(dr. a. c. oudemans). nkw list of dutch acari, I. 171 



Phthiracarus arduus (G. L. Koch). 



have observed many specimens; they have not smooth, but 

 somewhat feathered bristles. The pseudostigmatic organs too are 

 somewhat feathered, especially distally. I think Michael has over- 

 looked this — or the Dutch specimens differ from the British. 

 I believe PJdhiracarus canestrinii Michael to be the same species. 

 I have arduus with pseudostigmatic organs standing between a 

 common rod-like and one « with thin peduncle and flattened 

 expanded head ». The length of this organ is varying too , the 

 shorter ones are nearly straight, the longer ones curved. These 

 varieties are local ones. 



Arnhem, 12 Febr. 1900. 



