6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 23 



At the time when the aeschnid imago is ready for ecdysis, the larval 

 cuticle splits along the middle of the back on the thorax and the first 

 abdominal segment. On the head (fig. 2 C) the cleavage line continues 

 over the vertex to the frontal region, where it forks laterally around 

 the frons and then curves outward through the corneae of the com- 

 pound eyes. The ecdysial split on the head follows this course in most 



Tnt 



Fig. 2. — Anax Junius (Drury). 



A, head of larva, anterior. B, same, ventral view, with mouth parts and mem- 

 branous ventral wall of head removed, exposing hypopharyngeal apodeme and 

 tentorium. C, cuticle of larval head after ecdysis, showing open cleavage line. 

 D, head of adult male, anterior. 



a, ventral articulation of mandible ; a', articulation of maxilla ; at, anterior 

 tentorial pit ; Clp, clypeus ; IiAp, hypopharyngeal apodeme ; Hphy, hypopharynx ; 

 Lm, labrum ; Md, mandible ; Mx, maxilla ; pos, postoccipital sulcus ; pt, posterior 

 tentorial pit; Tnt, tentorium. 



Odonata, both at the larval moults and at the final transformation, but 

 it shows variations in different forms and in some it does not invade 

 the eyes. 



The head of the adult dragonfly is fully formed within the cuticle 

 of the larval head, but when the emerging insect extracts itself from 

 the larval skin, the head at once takes on a very different shape (fig. 

 6 G, H) . It is now hypognathous, the mouth parts hanging downward. 



