174 DEVELOPMENT OF THE WING-VENATION OP ODONATA, 



Stage 1. — .EschnincB [Austrophlebia, Austroreschna, Dendro- 

 cvschiia, uJ'Jschna, A'iiax^. 



Stage 2. — Synthemini [Synthemis, Metathews]. 



Stage 3. — Idocorduliiiii [^Aiist7'oco7'dulia\ 



StayeA. — Eiicordnliini + LibeHulina'[I/emico7'didia, Orthetrum, 

 Diplacodes; with Cordulephya a specialised offshoot from near 

 the base of the Eucorduliini]. 



Let us now study these four stages in turn : — 



Stage 1. — .EscJuiinoi (Figs. 1-3, and Plate xi., figs. 1-3). All 

 the genera studied under this stage, agree exactly, in the forma, 

 tion of their anal loops, with the description already given in the 

 case of ^Eschna hrevistyla{Yigs.\-o). In all cases, the basal side 

 of the loop is A2, and the proximal side is Aj, the latter fusing 

 with Cu2 for some distance, and finally turning inwards to com- 

 plete the loop below. 



Stage 2. — Synthemini (Figs. 5-8, and Plate xi., figs. 4-5). At 

 first sight, there seems to be very little difference between the 

 anal loop of the Synthemini and that of the ^EschnincB. But a 

 little consideration will show us that those forces which culminate 

 in the formation of the complex Italian loop are already at work. 

 Two important changes are beginning to take place : — 



(1). Ac bends off from Cu + A much closer to the base of the 

 wing than to the triangle. [In Stage 1, it bends off somewhat 

 nearer to the triangle than to the base, while in the Gomphinoi 

 it is still nearer to the triangle]. 



(2). Consequently Aj is stretched longitudinally, tends to de- 

 crease in diameter, and makes a weaker union with Cug. 



Probably the larva of llacromia will be found to exhibit a 

 similar arrangement, though we must not be too hasty in assum- 

 ing a near relationship between this genus and the Synthemini. 

 Metathemis agrees exactly with Synthemis. 



This stage shows the first attempt to enlarge the basal area of 

 the hindtving. It is carried out on very simple lines, viz., by a 

 purely longitudinal stretching of the area between Ac and the 

 triangle. Developed to its logical conclusion, it culminates in 

 such forms as Synthemis regina $ and 9, in which the enor- 

 mously widened anal loop is split into two by the development 



