XI] THE REPRODUCTIVE SYSTEM 225 



its eggs, and the latter are of the rounded form found in all 

 Libellulidae. 



(iv) By reduction of the median processes to mere vestiges, 

 and a decrease of the anterior processes to small flaps, we reach 

 the stage seen in many Libellulinae and Gomphinae. Finally, 

 the former quite disappear, while the latter become either the 

 small valvula vulvae or the bifid or complete vulvar scale (fig. 103, vs) 

 situated on the anterior side of the genital pore. 



A few Libellulinae (e.g. Uracis, fig. 104) have recently reacquired 

 a distinct ovipositor, by elongation of the vulvar scale into a 

 sheath-like process projecting from segment 8. A similar process 

 is developed from segment 9, from near the basal rudiments of the 

 original median processes ; it is softer, and fringed with stiff hairs. 

 The valves are absent. 



We may sum up the position, as regards the gonapophyses, in 

 the following table: 



Fate in ? 



Order of Zygoptera 



Develop- Aeschninae & Cordule- Gomphinae & 



Name Segment Position ment Petalurinae gastrinae Synthemini Libellulinae Fate in c? 



nterior 8 median 3 ^ \ basally fused vulvar absent 



Processes ventral terebra , or much scale 



or [ hy t P r 6 o r Dhied reduced 



edian 9 ^ I aculeus I reduced or vestigial absent 



Processes absent or absent 



ateral 9 latero- 1 valves vestigial vestigial vestigial valvules 



Processes ventral or absent or absent 



The Process of Oviposition (figs. 105-108). 



As the form of the ovipositor is closely correlated, not only 

 with the method of oviposition, but with the shape of the egg, 

 it will be advisable to deal with both of these here. 



We may classify the method of oviposition broadly into two 

 divisions : 



(1) Endophytic Oviposition, or the placing of the eggs in the 

 stems or leaves of aquatic plants, or other objects close to or 

 under the water. Correlated with this habit are (a) the complete 

 form of ovipositor, and (b) the elongate form of egg. 



(2) Exophytic Oviposition, or the dropping of the eggs freely 

 into the water, or in other ways placing them outside the tissues 

 of plants. Correlated with this are (a) reduction of the ovipositor, 

 (b) the rounded form of egg. 



T. D.-F. 16 



