inn 



seem espet-ially titted for the insertion of tlie abdominal appendages of 

 the male. But from direct observation it is l<:no\Yn tliat tlie male holds 

 tlie female \>\ the prothorax, probably by the encirclini;- juroove at its 

 anterior end. Moreover, because this structure is covered liy the posterior 

 lobe of the prothoi-ax. it would be impossible for the male to reach it. 

 See Plate II. Fis;. 2. 



Nevertheless this structure must in some way be involved in the act 

 of copulation. It is interestinn' to note that in the Anisoptera where the 

 male holds the female by the head instead of by the thorax this peculiar 

 structure is not developed at all. 



I'.ut whatever its function, or wiiether it has a function or not, its 

 f(irm is sutHciently different in the females of the different species of 

 Arnia, and sutflciently constant among those of any given species to 

 warrant its use in classification. How far this structure is good in show- 

 ing relationships, it is ditficult to say. According to it putrida would fall 

 in a very distinct group by itself. AipcaJis would fall by itself. Violacea, 

 f<r(U(la. and tibialis would fall in a group by themselves, in which violacea 

 and scdiiln would be much more closely related than either to tibialis. 



A key to females may be constructed as follows: 



A. The ear-; entirely al)sent. The whole structure wide l.-Uerally and 



narrow from front to back aiiiralis. 



AA. The posterior edge of each wing produced into a ))road rectangular 

 lobe. The median longitudinal fossa of the base broad and 



shallow putrida. 



AAA. The posterior diHile of each wing produced into an ear. The median 

 fossa relatively deep. 



li. The apex of each ear pointing forwards and upwards. 

 The entire structure relatively deep from front to l)ack. 



tibialis. 

 Bli. The apex of each ear i)ointing upwards and backwards. 

 ('. The cavity very narrow. The ears broad and tlat, 



riolaeea. 



CC. The cavity of usual width. Tlie jjosterior edge of 



each ear turned up sediila. 



