ACARINA FROM THE JUAN FERNANDEZ ISLANDS 603 



3rd joint short, triangular in outline, with two slender hairs, one external, 

 one internal, curved forwards and upwards. 4th joint short, with two long 

 dorsal hairs in the middle and one marginal ventrally which curved forwards 

 and upwards like an S on the exterior side, 



5th joint long, cylindrical, about 3 times as long as its diameter, cut off 

 obliquely from the dorsal side at the top, where there are three very slightly 

 curved, hyalin, pointed bristles of subequal size, arranged like the teeth of a 

 comb; a little in front of the middle there is a larger, slightly curved, hyalin 

 bristle, inserted on a low projection, which as pointed out by the author (1910, 

 p. 496—^97) in reality consists of two bristles pressed closely together; behind 

 this there is a curved hair of medium size. 



Hysterosoma. The hairs of the dorsal side are either very inconspicuous 

 or absent. The areae porosae on the other hand, are very conspicuous, after 

 proper treatment with lactic acid. The areae porosae adalares are large, eongated, 

 with rounded ends, tapering outwards and about 4 times as long as they are 

 wide; they are transversal, with the longitudinal axis forming an almost right 

 angle with the lateral margin of the body and finely punctured. 



Only one pair of areae porosae mesonoticae, which seem to be shaped like 

 a horse-shoe with the concavity turning inwards. As a matter of fact at greater 

 magnification the areae appear to be oval, on the lateral side surrounded by a 

 narrow band of slightly thickened cuticle; on the inner side there are two 

 rounded lobes of subcutaneous glands (fig. 108). With oil immersion the areae 

 seem to be densely covered with exceedingly minute cuticular spines, but the 

 structure is very difficult to see plainly and it may be that what appears to 

 be spines are in reality fine canals penetrating the cuticle of the areae porosae. 



Near the hind margin there is a pair of large, rounded areae porosae pos- 

 teriores, the longest diameter of which is ^U of that of the areae porosae ada- 

 lares; between them there are about 5 pairs of smaller, rounded pores and on 

 lateral view we notice a row of small rounded pores along the sides, not visible 

 from above. 



The pteromorphae project forwards almost as far as the top of the 

 rostrum, the fissure is very distinct and directed forwards parallel to the an- 

 terior edge of the pteromorphae. When the pteromorpha is dissected and 

 viewed from above the fissure is seen to be a groove, rounded inwards, where 

 it is broader and gradually disappearing towards the middle of the pteromorpha. 

 The anterior edge of the pteromorpha is concave, forming an even and sym- 

 metrical curve, the lateral edge has a wide, rounded incision. 



Loc: Juan Fernandez, Masatierra, among dry leaves Aug. 1917. 



18. Pergamasus crassipes (L.) var. longicornis Berlese. — Figs. 109— no. 



This very widely spread species seems either to be subjected to a great 

 variation, or else it is composed by several closely related species, the males 

 of which have almost the same armature of legs II. 



