ACARINA FROM THE JUAN FERNANDEZ ISLANDS 6p7 



Upper jaw with numerous teeth, the largest one being inserted opposite 

 the median tooth of lower jaw; in front of this the edge is excavated, with 4 

 small teeth, pilus dentarius being inserted on a level with the last of these; 

 further backwards a small tooth, then a thin blade, then a rounded incision 

 and then a small, blunt tooth. 



Loc: Juan Fernandez, Masatierra, among dry leaves. 



20. Sejus insulanus n. sp. — Figs. 118— 120. ' 



Amongst the dry leaves mentioned above (p. 587) there was also a specimen 

 of Sejus, a female, much shrunken and deformed but nevertheless well enough 

 preserved to be described. Hitherto only two species of Sejtis (taken in modern 

 sense) seem to be recorded from America, S. americanus Banks and S. pari- 

 comis Berlese from Buenos Aires, previously wrongly interpreted as S. acan- 

 thurus Berl. (comp. Berlese: Centuria seconda di Acari nuovi. Redia. Vol. 

 XII. 1916, p. 150). 



The present species is easily recogni;^ed by the short projections at the 

 posterior margin. In neither of the american species is the exceedingly re- 

 markable shape of the sternal and genital shields described. It is, therefore, 

 impossible to compare the present species with these. I must confine myself 

 to the european species S. togatiis K. of which I have material collected in 

 Sweden. 



Length 660 {i, width 420 [i. 



The shape and structure of the dorsal shields I have not been able to 

 see distinctly. There is a marginal shield which is very narrow as far as 

 to the middle of the ventri-anal shield but widens further backwards towards 

 the posterolateral angle. It bears 2 — 3 rows of short, cylindrical projections 

 each bearing a stout, short pointed bristle, curved sharply backwards and 

 slightly serrated. At the posterolateral angle there is a longer, conical pro- 

 jection carrying a larger bristle and at the posterior margin there are two pairs 

 of projections slightly larger than the lateral ones and carrying larger bristles 

 curved towards the middle. 



Ventral side (fig. 119). The sternal and genital shields are of a very 

 peculiar shape, quite unique amongst the Mesostigmata. It is, therefore, very 

 deplorable that neither Berlese nor Banks have paid any attention to these 

 structures. Already in 1912 I described them briefly in Sejus togatus K. (1. c. 

 fig. 29, 30, p. 19). 



As a matter of fact these shields and the number of hairs on them are 

 so different from anything hitherto known amongst the Mesostigmata that one is 

 at a loss how to interpret them. As a rule there are on the sternal and genital 

 shields in the female in all 5 pairs of hairs, of which 4 pairs belong to the coxal 

 plates of legs I — IV and one pair to the epigynial shield (compare TragArdh 

 1 91 2, figs. 21 — 24). In Sejus insulanus and S. togatus^ on the other hand, we 

 find in the space between the coxae in all 7 pairs of hairs, of which 4 pairs 

 are placed far forward between coxae II, and 3 pairs along the sides of the 

 epigynial shield. 



