XORTH AMKRICAN ODONATA. 185 



The spermatozoa of the Agrionidee and the Aeschiiidpe are very 

 slender, very agile and of hair-like form, while those of the Libel- 

 lulidse are thicker and immobile (Siebold 17). Several stages in the 

 development of those of Agrion puella and Calopteryx virgo are de- 

 scribed and figured by Butschli (Zeit. Wiss. Zool. XXI, pp. 528, 

 529, pi. xl, 1871). 



The external genital organs of the male are separated from the 

 orifice of the duct of the testes and lie in a pocket on the ventral 

 side of the second abdominal segment, entirely outside the body 

 cavity and having no communication with it. They consist of a 

 jjenis and its vesicle, lying in the median line, and on either side of 

 these one (LibellulidiB) or two (Aeschnidte, Agrionidse) pairs of 

 processes — genital hamules (see PI. II, figs. 3-6). The vesicle of 

 the penis is a sack with chitinous walls, lying at the hind end of the 

 pocket and firmly attached at its basal end to the anterior portion 

 of the sternum of 3. Its distal extremity may (Anisoptera) or 

 may not (Zygoptera) be attached to the penis. In the former case 

 the penis is a three-jointed, chitinous tube, bent ventrally on itself 

 and then directed backwards, with its cavity (lumen) continuous 

 with that of the vesicle ; a longitudinal opening to the exterior is 

 present on the convex side of the second joint, and the apical, or 

 third joint terminates variously in difierent species. In the latter 

 case the penis is ucjointed, and is attached to the floor of the pocket 

 (('. e. to the sternum of 2). In either case the penis is situated imme- 

 diately in front of the vesicle. The hamules are variously shaped ; 

 the anterior pair is the larger in the Agrionidse and the Aeschninse, 

 the smaller in the Gomphinse ; the single pair present in the Libellu- 

 lidse corresponds to the posterior pair (Hagen, 39, pp. 273-74). In 

 front of the anterior pair, the anterior sternal border of 2 forms a 

 variously-shaped, downwardly-projecting piece — the anterior lamina 

 — which forms the front boundary of this genital pocket. Between 

 the hamules, and immediately in front of the penis, there is in the 

 Aeschnidse, and to a less extent in the Agrionidse, a median, hood- 

 like, chitinous piece, under whose arch the penis is folded when not 

 in use. This is the sheath of the penis.^ In the Libellulidte this is 



* It is here to be remarked that de Selys and Hagen (40, 43, and in their Revue 

 des Odonates d'Europe) have applied the term "sheath of the penis" (gaine du 

 penis), not as by Eaiubur (33) and as above, but to the vesicle of the penis. Mobile 

 the real sheath of the penis is called the cuillere. Ranibur's description is very 

 clear, and his terms are followed iu the text. Hagen uses the term " vesicle of 

 the penis" iu (36). 



TRANS. AM. ENT. SOC. XX. (24) AUGUST. 1893. 



