420 Anuals of the South African Museum. 



specimens very narrowly whitish at proximal end. Immature males 

 similar to female, but black bands of abdomen broader, very gradually 

 passing to mature colour ; vestiges of thoracic pattern often visible in 

 partly pruiuose specimens. 



9 . Labium yellowish, median lobe, and sometimes a narrow median 

 line on side lobes black. Labium, face and frous yellow ; broad basal 

 black band on frons, extending anteriorly into furrow. Thorax and 

 abdomen light greenish-yellow with black markings ; cuneiform band 

 narrower dorsally, on median suture ; lines very close to humeral 

 suture, on humeral suture, half way to metastigma, on metastigma, 

 on second lateral suture, on metepimerou ; these lines, except the 

 sutural ones, mostly dorsally incomplete. Abdomen with broad, slightly 

 sinuate mid-dorsal band, narrow lines on lateral and transverse 

 carinae, broader 011 segments 7-9 and confluent with dorsal black. 

 Wings slightly stained with greyish yellow throughout; deeper yellow 

 but very diffuse spots at nodus and variable yellow basal spot on 

 second pair to Anq^, Cnq and end of membraiiule in specimen from 

 Johannesburg. Legs black, with light yellow lines on external side 

 of femora. 



cJ , Abd. -27, hd ic. '29, pt. 3 mm. 9 , 25, 29, 3'5. 



This is one of the characteristic Libellulinae of the South African 

 fauna, though extending northward to British East Africa. It 

 resembles strangely Trithemis Distanii, not only in colour but even in 

 genital structure of male, though H. dorsalis has the wings com- 

 paratively more elongate than T. Distant i and their venation more 

 close. Males may further be distinguished by their hamule being 

 higher (especially the basal part) than in Distatiti ; females and 

 immature males of Distanti show the black lines of thoracic sides 

 with a distinct tendency to longitudinal fusion, common to almost 

 all species of Trithemis; in H. dorsal is these lines are very sharply 

 denned and there is no indication of longitudinal fusion. Kirby had 

 described (1905) the genus as new under the name Misthotus, and 

 the male from slightly different individuals as M. ainbiyuws and 

 M. Marshall i. The descriptions of Helothetnis (Karsch) and of the 

 species dorsalis (Rambur) were made from the female. The highly 

 dimorphic sexes were united under the older name by the writer. 



TRITHEMIS (Brauer, 1868). 



A genus of wide distribution in tropical Asia, tropical and sub- 

 tropical Africa, the greater number of species African. Together with 

 Orthetruiu it is the dominant African genus of Libellulinae in number 

 of species and of individuals. 



