1G5 



As far as I know the "iimiiot/niphic spccidJc'' was ni'ver published. 



Calvert, too. in a paper wliieh has just appeared on the genus Arc/i'i, 

 recognizes this structure.* 



This structure occurs.' as far as 1 have examined, in all the native 

 genera of the Zygoptera. l)ut it is lacking entirely in the Anisoptera or 

 possibly is replaced there by the low transverse carina across the extreme 

 anterior end of the mesepisternum. It is found on the same general plan 

 in the diffei'ent genera, consisting of a heart-shaped enlargement of the 

 mid-dorsal carina, on either side of which is a triangular wing with its 

 apex running down to the mesinfraepisternum. 



ArtXer.or bordei cf \ J 

 rr.;i3;jist<?.num. 



J- -^.ad.-rsj/cd 



In the genus Argia a more or less oblong depression (cavity— see figure 

 al)Ovei, bounded on either end l>y the high basal carina of either wing 

 (see tigure aljove) occurs in front of the heart-shaped end of the mid- 

 dorsal carina. The basal carina of each wing ends in front in a horn, 

 and behind, in the case of the females of four of the five species, in an 

 ear-like lobe (the ear— see tigure above). In the male no elaborate ex- 

 pansion into an ear occurs. The most striking differences in this structure 

 are those of the size and shape of the ears. As these ears are absent in 

 the males, for them the structure loses most of its diagnostic value. How- 

 ever, for interest in comparison, figures of this structure as it occurs in 

 the males of the five species are shown in the plate (see Plate II, Figs. 

 1. o, ."), 7 and !>i. By reference to them it will be seen at once that, in the 

 male, this structure is of a more generalized type than in the female. The 

 structure as found in the male is nearer the general type found in related 

 genera. 



The above would seem to indicate that this structure is a sexual organ 

 functioning in the female and merely iiassively present in the male. One 

 would ;it once juniii at the conclusion tliat it is the organ iiy which tlie 

 male holds the feinal,' during Tlie act of copulation. Tlu' cavitv would 



^Calvert, Bull, Mus. Cump. Zool Nov. 1902. 



