384 Annals of the South African 



spines or bristles on the inner surface of mentuni and lateral lobes 

 forming a kind of basket. When closed the labium covers the inferior 

 and anterior side of the head like a mask. Plate XII, fig. 5 and 

 fig. 6 represent two principal types of Libelluline nymphs. 



(a) The Orthetrum-tyipe : Head with nearly parallel sides, small 

 eyes, antennae inserted well in front of the eyes ; legs robust and 

 hairy ; integument opaque ; mostly living half-buried in mud at the 

 bottom of water. 



(fe) The iSympetrum-type : Head with sides very convergent pos- 

 teriorly, eyes large, antennae inserted scarcely in front of anterior 

 margin of eyes ; legs slender, less hairy ; living often free between 

 plants in this case semitransparent, greenish or yellowish, often with 

 a rich pattern of dark tints. 



In the following descriptions structural details of male and female 

 genital organs are generally omitted, though their diagnostic value is 

 evident in many cases of doubtful specimens. For the limited fauna 

 here concerned, amply sufficient distinctive characters were available 

 in details of colour, pattern and venation. The genital structures are 

 fully described, arid a great many of them also figured in the writer's 

 monograph of the LibeUulliiae it was therefore not desirable to repeat 

 descriptions and figures here without diagnostic necessities. The only 

 exception was made for the genus Orthetrum, where the male genital 

 structures are indispensable for identification of many specimens with 

 the original pattern covered by the blue pruinosity of adults, and where 

 these characters are the only sure guide in a very intricate group of 

 closely allied species. 



1. Arc ulus distal to second Anq. (Plate X, fig. 4) . . . 2. 



Arculus proximal to second Anq. (Plate XI, figs.) . . . .4. 



2. Last Anq in front wing complete . ...... 3. 



Last Anq in front wing incomplete, existing only in costal field, ending 

 at the subcosta. 2 Cuq in hind wing. Proximal side of t in hind 

 wing a little distal to arculus. t free in both wings. Dbcoidal 

 field in front wing beginning with two rows of cells ; 3/ 4 and GUI diver- 

 gent from a level proximal to nodus, the field considerably widened to 

 wing's edge. No distinct Mspl. One row of cells Rs-Rspi. 10j Anq. 

 Posterior lobe of prothorax large, erect, ciliate. Abdomen short, slender 

 and slightly fusiform in <J , robust and cylindrical in <j? . Third femora 

 with 4-5 ( $ ) or 8 ( $ ) long and robust spines. ? with margins of eighth 

 segment folded ; vulvar scale small Porpax. 



3. Discoidal field in front wing beginning with one row of cells. l/ 4 and CM, 



divergent from a level proximal to nodus, discoidal field much widened 

 to wing's edge, t in front wing almost equilateral ; proximal side of t 

 in hind wing a little distal from arculus. t free in both wings. 2 Cuq 



