300 



been in the » occasion to observe this organ in the large Trom- 

 bidiums of the intertropical regions (Thrombidium tinctorium, etc."). 

 He then describes the crista of Thrombidium tinctorium, and does not 

 make any mention of those of the »etc." species. I cannot believe 

 that the crista of Thr. dugesi and Thr. gigas are perfectly the same 

 in all details as that of Tr. tinctorium. In this description he 

 compares the pseudostigma with a thimble, and indead it is a 

 hyalin thimble-like cup. Also the pseudostigmatic organ is well 

 described by him. Both pseudostigma and pseudostigmatic organ 

 are further compared with the same organs of Oribatidae. 



It was however already in 1885 that Berlese compared these 

 organs of Tarsonemidae with those of Oribatidae which led him 

 even to unite these two families into one group. At present we 

 know that Tarsonemidae are in no relation with Oribatidae, but 

 are Prostigmata, like the Thrombidiidae, so that they even are 

 united by some authors with the last mentioned family into one 

 and the same group. 



Then (p. XLV, sqq. of the same Bulletin) Dr. Trouessart 

 compares the two areolae with their pseudostigmata of Thrombidium 

 tinctorium in particular, and those of the Thrombidiidae in general 

 with the pair of median eyes of Smaris lyncaea, and on the 

 likeness of these two different organs he bases a hypothesis which 

 derives the areolae with their pseudostigmata from median eyes. 

 Now I think this hypothesis crumbles at once as Smaris lyncaea 

 has no median eyes at all! This so called pair of median eyes 

 are nothing else but again areolae with pseudostigmata! (See my 

 paper »Drei neue Acari von der Insel Juist", — Abh. Nat. Ver. 

 Brem. 1901, v, 17, p. 226). 



Therefore we should only have to compare the position of the 

 areolae with the median eyes of Gigantostraca, Xiphosura, Scor- 

 piones, Thelyphones, Phrynes, Araneae, Galeodeae, Phalangida and 

 among the Acari'. of the genera Limnochares and Eulais, which 

 latter, like the areolae of Thrombidium, are enclosed within a 

 chitinous apparatus. 



But, if we are comparing, we are obliged to admit another 



