307 



hypothesis, viz. that the single median eye of the genera Michae- 

 lia, Ammonia (both Thrombidiidaé), Uydryphantes, Thyas, Eupatra, 

 etc. (all Hydrachnidae), has its origin in a confluence of the two 

 inedian eyes of their ancestors. And if this is adopted, we must 

 go farther and reason, that it is very probable that the single 

 inedian pigment-spot of Halacaridae is originated from a single 

 median eye of their aucestors. But alas, what rests of the 

 hypothesis, since I have found in the same larva of Thrombidium 

 areolae (pseridostigmata) together with a median pigment spot? (This 

 curious larva will be described and figured in a subsequent con- 

 tribution to the knowledge of Acari). 



On p. 87 of the Annales de la Société Ent. de Fr., 1894, Dr. 

 Tbouessart writes, that he possesses a large quantity of larves of 

 Thrombidiums of warmer regions, and also some larvae called 

 Tlazahuatl in Mexico. Further he says: »Elles ne différent ni par 

 la taille, ni par aucun caractère de valeur spécifique, de notre 

 type indigène pas plus qu'elles ne différent entre elles". It is 

 impossible to me to agree with him, since I have examined 

 six different larvae. They widely differ one from another! But 

 I agree with him where he asserts : »il est impossible de déter- 

 miner 1'espèce a laquelle elles se rapportent". Yet it is a pity 

 that he has not described and figured the different larvae in his 

 possession, for the knowledge of these larvae, their segmentation, 

 their pseudostigmata, their pseudostigmatic organs, their » Ur- 

 tracheeen", and their dermic shields is of great value. 



On p. 88 he asserts that Thrombidium tinctorium »se décolore 

 complètement". In how much time, I may ask, for my specimens 

 of 1889 and 1896 are yet coloured light vermillon. In dissecting 

 my Thrombidium tinctorium a kind of coloured oil flowed out of 

 the abdomen of one of my 9- Dr. Trouessart states that only 

 Thrombidium gigas possesses »de gouttelettes de graisse fortement 

 colorée en rouge orangé". 



On p. 90 he cites amongst the characters of Thr. tinctorium: 

 »Ongle du palpe dépassant 1'extrémité de la massue du dernier 

 article". We have only to contemplate my fig. 48, which is drawn 



