105 



A SHORT SURVEY OF THE MORE IMPORTANT FAMILIES OF 



ACARI. 



By Dk. a. C. OUDEMANS. 



MiTES or AcARi belong to the class Arachnoidea, which also contains the 

 Scorpions, the Spiders, the minute False-Scorpions, the long-legged Field 

 Spiders and some other curious eight-legged creatures. They are at present 

 considered as a degenerating branch o£ the Arachnoid trunk. Their larvse 

 are six-legged, their nymphs eight-legged, but deprived o£ genital apertures. 



Apart from the Ticks (Ixodoidea), mites have been generally very much 

 neglected by collectors and systematists alike ; but seeing that they comprise 

 a considerable number of species of undoubted economic importance, it has 

 seemed desirable to call attention to them by this brief account of some of 

 the more strikino- forms. A fuller investioation of their habits and life- 

 histories, especially as regards tropical species, is certain to yield much 

 information that is likely to be of both practical value and scientific interest. 



The AcARi full into the following natural groups : — 



(1) XoTOsTiGMATA. — A group of most interesting creatures of about two 



Fig'. 1. — Opilioacarus sef/mentattis, With; female; dorsal side; S== stigmata. 

 Copied from With, in Yid. Medd. Nat. Fo/en. Kjbhvn., 1904, tab. 1. 



to three millimetres in length, with hard integument, and resembling some- 

 what the well known Field Spiders. It is still doubtful whether they are 

 AcARi or not. They breathe b}' four pairs of dorsal ])reathing-openings or 



BULL. ENT. RES. VOL. I. PART II. JULY I9IO. L 



