ARTHUR DEWITT WHEDON 393 



straight region of quite even diameter throughout most of seg- 

 ment seven (the ileum, the three divisions of which cannot be 

 made out); a decided bulbous enlargement throughout most of 

 the eighth segment (probably the pouched region of Carroll); 

 a short, constricted section entering segment nine; and a verj' 

 much thickened cylindrical region running through the ninth 

 segment and most of the tenth. This enlargement has three 

 broad folds along its whole length and between them thin, darkly 

 pigmented areas; one of these folds is mid-dorsal, the other two 

 latcro- ventral (anterior part of the rectum, of Carroll). The 

 hind part of segment ten is occupied by a small vestibule leading 

 to the anus, the walls of which are well supplied with tracheae. 

 Both Calopteryx niacidata and Hetaerina americana have the 

 same structure (plate XXI, figures 1 and 2 ; plate XXV, figure 22). 

 Calvert (1911, 1915) has shown this same nature for the "anterior 

 part of the rectum " in Thaumatoneura and Med slog aster. 



Keproductivc Organs 

 (Plate XXI, figures 2 and 3) 



The reproductive organs are relatively simple in the Odonata, 

 consisting of gonads, ducts, receptacles and accessory sacs. Each 

 of these is unbranched and the discharge of the products is by a 

 single genital pore. In 1896 Fenard reviewed and criticised the 

 work of Reaumur and of Rathke, and added the results of his own 

 dissection of Libelhda depressa adult. This accords with the 

 descriptions of Tillyard (1917). 



In the larvae these organs are of course only in partially de- 

 veloped states, and the writer knows of no descriptive work on 

 their stages of growth and maturation. Calvert (1915, plate 

 XV, ts and vd) indicates the male organs of a full grown larva of 

 Thaumatoneura, and also of Cora (1911, plate III, ts) but no 

 descriptions are given. Quite full grown larvae have been used 

 in the present study, and it is a very noticeable fact that the 

 Zygopterous larvae have, gonads as well developed as those of 

 even advanced teneral imagoes of the Anisoptera. A comparison 

 of the Lestes larva (plate XXI, figures 2 and 3) and the teneral 

 imago of Tramea (plate XXVIII, figure 38) indicates this. As 

 would be expected also the sex glands are relatively better de- 

 veloped and more conspicuous in the larvae than are the accessory 

 parts. 



TRAXS. AM. EXT. SOC, XLIV. 



