The Nymph. 



35 



imperfect rectal respiratory system.^ Between the pro- 

 notum and the meso-notum in the full-grown n}-mph will 

 be found a pair of large spiracles (Fig. ii, m.s.) (some- 

 times plainly visible), while another smaller pair occur 

 just above the hind-legs. Immediately before emergence 

 the former pair are probably open, 

 and used for breathing atmospheric 

 air. The eight pairs of abdominal 

 spiracles appear to be functionless 

 during the nymph-stage. 



In connection with the structure 

 of the Dragonfl3'-nymph the most 

 striking point is the mask f'Fig. 

 13, ;//.), a peculiar modification of 

 the labium, or lower lip, by means 

 of which the creature catches its 

 pre}'. The term mask is applied 

 to this structure because it hides 

 the lower part of the face. At 

 rest, with the exception of the tip, 

 the mask is out of sight (Figs. 11 

 and 12). The base is attached 

 below the mouth ; the hinder half 

 lies under the head and fore part 

 of the thorax ; there is a joint in 



the middle, and the fore part lies under the hinder, 

 bringing the base and tip together close to the mouth 



Fjg. 13. — Side-view of 

 FoRE Part of a 

 Nymph with Mask 

 in situ. 



II!., Mask: It., Hinge; t.. 

 Tip of Mask; Jii.h., Movable 

 Hook attached to Palpus. 



* The five anal appendages of the Libellulidcr vary much in size and 

 shape, as also do the lamella; of the Ai^rio?iid(r. One or two of the 

 latter are to be seen in Figs. 41, 45, 47, and 53, from which it will lie 

 noticed that the differences are considerable, and it may be that wlien 

 more is known of the Agrionine nymphs the lamella; may be found to 

 be of use in helping to distinguish the sjiecies. 



D 2 



