Mesostigmata 105 



3. Proz^rco^ Willmann, 1943 



Type. Zercon fimhriatus Koch, 1839 



4. Seiodes Berlese, 1887 



Type. Seioides ursinus Berlese, 1887 



5. Triangulazercon Jacot, 1938 

 Type. Zercon peltatus Koch, 1836 



(= Zercon triangularis Koch, 1836) 



6. Trizerconoides Jacot, 1938 



Type. Zercon radiatus Berlese, 1910 



Discussion: Zerconids belong to the large fauna that inhabits the 

 upper layers of the soil, litter, and beds of moss. They are of no known 

 economic or medical importance. 



Rejerences: 



Jacot, A. P. 1938. The Geenton mites of Florida. Florida Ent. 21:49-57. 

 Tragardh, I. 1946. Outlines of a new classification of the Mesostigmata 



(Acarina) based on comparative morphological data. Lands Univ. 



K. Fysiogr. Sallsk. Handl. N. F. Bd. 57 Nr. 4:1-37. 



TRACHYTINA TRAGARDH, 1937 



Tragardh 1941 gives a good account of this group (cohort of Tra- 

 gardh) and he divides it into three families that are obviously closely 

 related. Therefore, a diagnosis of the group will be given along with 

 Tragardh's key to the families, and a separate diagnosis for each fam- 

 ily will be omitted. The same plan will be followed for the discussion 

 and reference in order to avoid repetition. 



Diagnosis: They are intermediate between the Gamasides and Uro- 

 podina. The articulations of coxae i are similar to the Gamasides in 

 that the coxae do not cover the broad-based tritosternum. The genital 

 openings are similar to but not identical with those of the Uropodina. 

 The metasternal plate in the female is not fused with the sternal and 

 ventral plates and is situated lateral to the epigynial plate. In adults 

 the dorsal surface is covered by nymphal skins. The habit of the reten- 

 tion of the cast nymphal skins is unusual in the Mesostigmata and is 

 restricted to the Trachytina. However, several of the Oribatei exhibit 

 this peculiar phenomenon. 



