XI] THE REPRODUCTIVE SYSTEM 227 



In the Aeschninae, some forms lay their eggs in soft tissues,, 

 as do the Zygoptera. The eggs are, 

 however, generally more neatly and regu- 

 larly arranged (fig. 106). This may be due 

 to the increased efficiency of the styles, 

 which perhaps measure off the distance 

 between successive incisions. The terminal 

 bristle or hairs would assist in this process. 

 In the Brachytronini, the eggs are placed 

 either in hard wood or in the matted 



roots of mosses or filmy fern growing on 



J Fig. 106. Section of reed- 



damp rocks. The hard wood is sawn stem to shew eggs of 



across transversely by the dentigerous 

 plate, before the egg is inserted. The 

 process is slow, and attended with much danger to the Dragonfly, 

 which shews great trepidation, and often leaves its sawing uncom- 

 pleted. The oviposition of Gynacantha has not been observed. 



Turning now to the exophytic forms, we have already noticed 

 Cordulegaster (p. 223). In some Synthemini, the large fused anterior 

 processes help to regulate the flow of eggs, and to prevent them 

 from exuding too far. In the great majority of cases, the Dragonfly 

 lays her eggs while flying over the surface of the water, merely 

 by striking the tip of the abdomen from time to time against the 

 water, and so washing off the steady flow of exuding egg-masses. 

 The gelatinous substance surrounding these masses seems to 

 dissolve on contact with water, so that the eggs spread out on 

 the river bed. Gomphinae usually oviposit in the ripples of fast 

 streams, Libellulinae over still water. This method of oviposition 

 culminates in the genus Cordulephya, where the female performs 

 extraordinary evolutions, with sudden dashes down to the water 

 to lay its eggs. The movements are so swift and unexpected that 

 the insect is almost invisible, and very difficult to capture. 



In the genera Tetragoneuria (fig. 107) and Sympetrum, the eggs 

 are laid in gelatinous ropes, attached to submerged twigs. A 

 number of females help in adding to the length of rope, which 

 may contain many thousands of eggs. It seems clear here that 

 the gelatinous envelope does not dissolve, but rather tends to 

 harden in the water fioo]. 



152 



