Monhystera filiformis
Bastian, 1865

Female, length 1/44"; breadth 1/111".
External Characters.- Body long and narrow, scarcely tapering at all anteriorly, but narrowing behind vulva, and thence onwards, so as to terminate in a long filfiform extremity.  Head truncate; no setae.
Oesophagus 1/5th of total length.  Intestine sparingly covered with fat-particles.  Anus 1/160" from posterior extremity.  Vulva considerably behind middle of body.
Male not seen.
Hab. About liverwort, from pier of bridge, just above water-level, river Blackwater.
(Description- Bastian, 1865)

L = 0.61 mm; a = 24.1; b = 5.8; c = 4.5; V = 63
Male unknown.
Body of female almost straight when relaxed.  Head approximately 8 um wide and cephalic setae short, 2 um long.  Stoma simple, weakly sclerotized and V-shaped.  Amphid with a diameter of 3.2 um and situated 12.6 um or approximately 1.8 head width from anterior end.  Base of esophagus slightly expanded and esophago-intestinal glands rather large.  Tip of ovary approximately one body diameter from glands.  Vulva and vagina simple without special features, but just posterior ot the vulva a 'cell' occurs which was mentioned and illustrated by Andrassy (1977).  Rectal muscles rather strong and rectum clearly visible.  Tail not 'filiform' as name indicates, but elongate-conoid with cylindroid distal part.  With long, slender setae scattered over the body surface.

Distribution and habitat.  The species is rather widely distributed in South Africa.  It has been found in the Witwaterstand, Pretoria, the Vaal River and also the Western Cape.  On the Reef it was found in Westdene Dam, Florida Lake and Natalspruit, in the Pretoria area in the Hennop and Jukskei Rivers, at the Barrage in the Vaal River and in the Western Cape in the Cedar Mountains neat Clanwilliam, in the Elgin area and in the Bot River near Caledon.

According to Thorne, 1929, only five specimens of this minute, agile species appeared in this collection.  It frequently appears in high mountain soils, especially those along streams and lakes.
(Description- Joubert & Heyns, 1980)