BY R. J. TILLYARD. 



877 



earliest examinable stage, R is strongly and definitely Ijranched 

 (Text-fig. 2, a). At a later stage (the exact instar is not noted, 



Text-fig.2. — Ontogenetic stages in the development of the laival wing- 

 tracheation in Odonata. a, Gomphn'<, very eaily stage, 1 mm. wing; 

 h, G'omphu-s, later stage, 3 mm. wing, Rs between Mj and M^ ; c, 

 Gomphus, last larval stage, Rs across Mj and M„ , and bridge [Br] 

 indicated; d, Lihel/iila, very early stage, 0"8mm. wing, Rs already 

 across ^Ij and Mo. a-c, after Needham ; d, drawn from a photo- 

 micrograph taken by Dr. F. Ris. 

 but it would appear to be the last but three), Needham shows Rs 

 thrown over Mi_2 just before it divides into Mj and M..^, and then 



