BY R. J. TILLYARD. 



205 



the region of the closed posterior stif^mata). Beyond this, they 

 diverge slightly, and pass close under, and a little to the inside 

 of, the pair of larger and open anterior stigmata (Stj) which lie 

 hidden in the fold between thorax and prothorax. 



Plr 



Fig. 20. 



Fig.20. — Austrolestes leda Selys, 9 . Diagram of tracheal system of 

 thorax in full-grown nymph, viewed from right side. The left visceral 

 trunk (VT) crosses over to become hitched on to the right second pedal 

 trachea (P2), and a remnant (Vr) forms a small loop attached to the dorsal 

 trunk (DT). The alar trunks (AT^, AT.^) arise from DT (anally), and end 

 (costally ) on the second and third pedal tracheae (pg, Pa) respectively. The 

 posterior stigma (Stg) is aborted, but its position is marked by tracheal 

 branchlets. The two dorsal trunks (DT) are connected by a short trans- 

 verse anastomosis (TA). For other letterings, see p.214. 



At a point not far removed from the thoracic anastomosis 

 (slightly behind it in jEschnid^, in front of it in Agrionidce), 

 each dorsal trachea gives off a strong branch to the second leg, 

 the second pedal trachea (pg). This important trachea receives, 



17 



