110 DRAGONFLIES [CH. IV 



transparent. It discharges several drops of clear fluid 

 from the anus. The fluid contains in solution nitrogenous 

 compounds akin to urea. The colours of the body sub- 

 sequently appear somewhat suddenly. 



The wings however are as yet but little larger than 

 those of the larva ; they stand out from the back with the 

 dorsal faces of right and left sides close together and the 

 apices hanging downward. At this stage they are very 

 soft and delicate and bleed freely if pricked or torn. The 

 ensuing conduct of the freshly emerged imago appears to be 

 designed for allowing the wings ample room for development, 

 without risk of injury, and for exposure to a free current 

 of air to aid in the drying and hardening. Often a few 

 steps upward are taken so that a direct hold is obtained 

 upon the support and the empty larval skin left behind. 

 The abdomen is now bent ventrally, i.e. the imago "hollows 

 its back," and the wings begin to expand. The process 

 sets in at the base of the wing, and in about half-an-hour 

 has extended up to the tip and the wings have reached 

 their full size, but are still opaque and of a dingy yellow 

 colour. Movements of the abdomen take place during 

 this process and suggest the possibility of the expansion 

 being caused by air being forced, in consequence of the 

 contractions of other parts of the body, in between the two 

 layers of which each wing is composed. The " hollowing 

 of the back" affords space (in the Libellulidce) for the 

 development of the bellying and more fragile hinder part 

 of the wing which would certainly be obstructed were not 

 the abdomen moved out of the way by this bending. 

 Some time, one or two hours, must yet elapse before the 

 wings are dry and firm enough to support flight. 



