Hydrachnellae 269 



Palpal segment iv long, awl-like and longer than segments ii plus 

 III; genital organ almost completely within deep genital indenta- 

 tion which reaches to posterior end of united epimera i; numerous 

 genital suckers on plates; body armored and highly arched; dorsal 

 suture separates dorsal and ventral shields Mideidae 



29. Body entirely armored; dorsal shield separated from ventral shield 

 by suture; inner margin of palpal segment iv does not surpass 

 proximal end of palpal segment v; segment iv not dorso-ventrally 

 broadened or thickened; genital organ with six to ten suckers; 

 epimera as a rule separated by suture in median line Mideopsidae 



Body unarmored dorsally and without dorsal suture; palpal seg- 

 ment IV dorso-ventrally thickened distally; inner side of palpal 

 segment iv surpasses proximal end of segment v and forms shear- 

 like organ; genital organ with many suckers; epimera without 

 median suture; posterior group medianly joined at angle 



Acalyptonotidae 



30. Four, six, eight or more usually disklike genital suckers are, as a 

 rule, in "lipfields" which lie in opening in ventral shield near inner 

 edge of the more or less valvelike, arched, but immovable genital 

 "rolls" 31 



Only genital lips, not many porelike genital suckers, lie in opening 

 of ventral shield; genital suckers do not lie in opening of ventral 

 armor but next to opening on more or less distinct, generally 

 winglike plates in ventral armor; genital suckers usually numer- 

 ous, small, and porelike; male often with appendage or petiole on 

 rear of body Arrenuridae 



31. Many small genital suckers A-Thienemanniidae 



Three to eight pairs of large genital suckers arranged in longitudi- 

 nal row Krendowskiidae 



The paper on the family Stygomonidae Szalay, 1943, type Stygo- 

 monia latipes Szalay, 1943, has not been seen at this date. 



Halacaridae Murray, 1876 ^ 



Figures 185, 186 



Diagnosis: The halacarids are trombidoidea with a body typically 

 flattened or, more rarely, circular in cross section and elliptical in out- 

 line. The mouthparts form a distinct capitulum which nearly always 



1 From Newell 1947. 



