88 



THE LARVA OE NYMPH 



[CH. 



less convexly arched, though they may become rather flattened in 

 very broad forms, especially at the sides. A definite trilobalion 

 of the abdomen is produced in the Petaliini (fig. 37) by the develop- 

 ment of rounded or sub-triangular upwardly-projecting lobes from 

 the sides of the terga. Extreme elongation of the last few segments 

 is a characteristic of some Gomphine larvae (fig. 186). The sternites 

 (B, 1-10) are rectangular plates, either flat or slightly convex. The 

 pleura (B, pi) differ from those of the imago in being strongly 

 chitinized. In the Anisoptera they form flat side-pieces to the 



C. 



Fig. 36. Types of Anisopterid larvae. A Ictinus australis Selys. B. Gomphus 

 vulgatissimus Linn. c. Macromia sp. (Indiana, U.S.A.). D. Austrocordulia 

 refracta Tillyard. E. The same, feigning death. F. Orthetrum caledonicum Br. 

 o. Diplacodes bipunctata Br. H. Tramea loewii Br. (Natural size.) Original. 



sterna; in the Zygoptera they are infolded. Eight pairs of 

 abdominal spiracles (B, asp) are present, the eighth being the 

 largest. Their positions, near the anterior margins of the pleura, 

 close to the terga, correspond with those of the imago. They are, 

 however, small and non-functional, the tracheal cords connected 

 with them remaining solid until metamorphosis. 



Dorsal spines may occur on the terga of some or all of the 

 segments, especially in running-water forms. Lateral spines 



