16 



THE IMAGO 



[CH. 



basal portion is shiny, slightly convex, and often brightly coloured, 

 forming a kind otfree or mandibular cheek, in front of the true gena. 



P 



Fig. 3. Mandible of Aeschna brevistyla Ramb. A. External view. B. Internal 

 view, i incisors; m molar. ( x 13.) Original. 



The teeth of the mandible are exceedingly strong. They lie from 



the distal end to near the base. 



They may be divided into two 



groups : (a) a distal group of three 



incisors (i), and (b) a large basal 



molar (m). The incisors are sharply 



pointed and slightly curved. The 



largest incisor forms the apex of 



the mandible. The molar has four 



cusps (originally, no doubt, separate 



teeth), set on a broad raised base in 



the shape of a Z. The cusps are 



placed one at each end and one at 



each angle of the Z. The structure 



of the mandibles is very constant 



throughout the Order. Biramous 



mandibles occur in a few archaic 



larvae. 



The First Maxillae (fig. 4). 

 These are jointed appendages, 

 slenderer, longer, and much less 

 powerful than the mandibles. 

 They lie between the latter and the lateral lobes of the labium, 



st 



Fig. 4. First maxilla of Avschna 

 brevistyla Ramb. ( x 15). c cardo; 

 il inner lobe; p palp; st stipes. 

 Original. 



