seem especially fitted for the insertion of the alKlominnl appendages of 

 the male. Bnt from direct observation it is known that tlib» male holds 

 the frmale liy the prothorax. pvoliahly liy the oncirclin.n' groove at its 

 anterior end. Moreover, because this strnctm'e is covered ))y the posterior 

 lolte of the jirothoi-ax. it would l»e impossi))le for the male to reach it. 

 See Plate II. Fig. 2. 



Nevertheless this structure must in some way l)e involved in the act 

 of copulation. It is interesting to note tliat in the Anisoptera where the 

 male linlds the female liy tlie head instead of by the tliorax this i)eculiar 

 structure is not developed at ali. 



P>ut wh.it(>ver its function, nv whether it has n fundicm or not, its 

 form is sutliciently different in tlie females of the different species of 

 Argia. and sufficiently constant among those of any given species to 

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

 ing relationshii)s. it is ditficult to say. According to it jnitrida would fall 

 in a very distinct group liy itself. Ai peal is would fall by itself. Tiolacea, 

 sfdnld. and tihiaJis would fall in a group l)y themselves, in which rinlacea 

 and scdiild wordd lie much more closely related than either to tibialis. 



A key to females may be constructed as follows: 



.4. The ear-! entirely absent. The whole structure wide laterally and 



nai'row fi-om front to ))ack apicdlis. 



AA. The jxtsti-rior <(li/r of each wing produced into a broad rectangular 

 lobe. The median longitudinal fossa of the base liroad and 



shallow piitrida. 



AAA. The /I'l^trrior (iin/lc of each wing producetl into an ear. The median 

 fossa relatively deep. 



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

 The eiUire structure relatively deep from front to liack. 



tibialis. 

 HB. The apex of each ear pointing upwards and backwards. 

 * ('. Tlie cavity very narrow. The ears broad and fiat. 



ridhicea. 



('('. The cavity of usual width. The posterior edge of 



each ear turned up scdiila. 



