328 ENTOMOLOGICAL NEWS. [ July, 'l6 



would have unhesitatingly believed that they represented at 

 least four genera. 5 



The only single character which runs through the entire 

 series is the absence of the internal soft fold. Probably the 

 spines along the shaft are also a character of the entire group 

 but they are so delicate that they have to be looked for spe- 

 cially, and in late rale and ad u stum I did not notice their ab- 

 sence until the drawings were assembled in the plate. An- 

 other character' which runs through the entire group, but 

 which is not so obvious, because it appears in a different form 

 in each species, is one or more outgrowths (septa, lobes, 

 spines, hooks, etc.) which appear along the median line of 

 the dorsal or internal surface of the distal lobe. Outgrowths 

 along this line, though they do occur in a few other genera, 

 are rare. The singular paired outgrowths of the lateral edges of 

 the distal segment, as they are developed in tcmporale, apicale, 

 graclle, ablutwn, ascendens, kennedil, cuyabae, and truncatuui, 

 are unusual, though they also appear in other genera. The 

 strangest and least comprehensible development in the entire 

 series is that of the pair of heavily chitinized hooks on the 

 apex of the distal segment in apicalc (Plate XVIII, fig. 3). 

 A strong chitinization at this point is all but unique among the 

 more than five hundred species of Zygoptera examined. The 

 terminal soft fold varies in development in this series but I 

 should hesitate to say that it was entirely absent in those 

 species in which it is not figured, as it is at times gossamer- 

 like and if the specimen is the least dry clings so closely to the 

 terminal segment that the most careful dissection may fail to 

 loosen it. However I can state that it is as a rule poorly de- 

 veloped except in chclijcrum, (PI. XVIII, fig. 26). 



The following brief notes are to amplify the characters 

 shown in the figures on Plate XVIII. 



Acanthagrion ablutum Calvert, figs. 10-11. The edges of segment 3, 

 twisted at its base and turned in, form a pair of "shelves" between 

 which is an ill-defined median septum. 



"Prof. O. A. Johannsen has just called my attention to a condition 

 similar to this in certain genera of Mycetophilidae. In some genera 

 in this family the hypopygium in the male varies between species so 

 much that the parts cannot be homologized. 



