258 Annals of the South African Museum. 



tergites, to which they are joined by a thin, transparent, completely 

 infolded membrane. There are rudiments of an eleventh abdominal 

 segment : supra-anal tubercle in female, superior appendage in male of 

 Anisoptera as rudiments of the tergite ; subanal plates in Auisoptera, 

 inferior appendages in male of Zygoptera as rudiments of the sternite. 

 The superior appendages of both sexes in the entire Order are con- 

 sidered by most authors as being appendages cerci of the tenth 

 segment. 



The disposition of copulatory organs in the male is another dis- 

 tinctive and unique feature in the Order Odonata. The opening of the 

 seminal vessel is constant, on the eighth sternite, covered by a pair of 

 small, roughly triangular, slightly projecting plates. But the copu- 

 latory organ is to be found on the second and third segment, where a 

 complicated pocket is formed of elements of the second sternite, 

 and a penis-like organ projects from the framework of the second 

 sternite in Zygoptera, and from the anterior margin of the third sternite 

 in Anisoptera. No detailed account can be here given of these very 

 complicated structures (cf. Erich Schmidt, " Vergleichende Morpho- 

 logic des ii und iii : Abdominal segments bei miinnlichen Libellen," 

 Zool. Jahrb. Anat., 1 xxxix, pp. 87-120, tab. 9-11, 1915). No use, for 

 diagnostic purposes, is here made of them in the groups Zygoptera 

 and Aeschninae ; but they are of great importance and comparatively 

 easy application in Gromphinae and Libellulidae. The G-omphinae 

 show in the appendages of the second steruite (1) a small anterior 

 lamina, (2 and 3) two pairs of hamuli, in the third sternite (4) a 

 cap-like organ which covers the penis, and (5) the penis itself. In 

 the Libellulidae the anterior lamina is somewhat more important 

 and only one pair of hamuli is present (the first pair is, as it appears, 

 fused to the anterior lamina) ; the ventral margin of the second 

 tergite is mostly produced in a flat organ, the genital lobe ; between 

 the genital lobes the penis is included, and no cap-like organ of the 

 third steruite exists. 



In the female no modification exists on the second segment. The 

 organs of copulation and oviposition have their regular position on 

 the eighth and ninth sternites ; eventually a modification of the tenth 

 partakes of the function. There are two rather widely different types 

 of organisation. The more simple type shows the genital opening at 

 the posterior end of the eighth sternite, either practically free, or 

 covered by a very simple chitinised plate, which is very often bifid to 

 various degrees ; the vulvar scale ; on the ninth sternite only two 

 minute styles or tubercles can be observed. This type is common to 

 the large family Libellulidae and to the Gromphiuae in the Auisoptera. 



