146 THE CANADIAN ENTOMOLOGIST. 



in America. As genera go the European Libelluhi depressa of Linnaeus 

 is certainly worthy to stand alone, and by all the recognized codes it has 

 the right to the original generic name. So that our N. American species 

 belong to Leptetrum, Newman ; Plathemis, Hagen ; Be/o/iia, Kirby, or 

 Holotania^ Kirby; and Kirby (1890 a Synonymic Catalogue of Neur. 

 Odon., London) has distributed our species rather freely among all these 

 genera. I now have nymphs of species referred by him to all the genera, 

 and, unfortunately, they do not confirm his arrangement of the imagoes. 

 The unknown nymphs still in the majority would doubtless lend the best 

 aid to drawing the lines where they belong. 



As implied at the outset, the nymphs described above differ by good 

 generic characters from all others known to me. They differ from all 

 Libellulid nymphs which I have seen by the entire absence of raptorial 

 setae from the mentum of the labium. They are distinct from the nymphs 

 representing the four genera named above by several additional characters : 

 by hooked teeth on opposing edges of the lateral labial lobes ; by the 

 extreme elongation of the abdominal appendages and especially by the 

 shape and relations of the 9th abdominal segment which is not longer on 

 the ventral than on the dorsal side, and consequently does not at all 

 appear to enclose the loth segment. The following characters of vena- 

 tion taken together appear to clearly segregate the imago : (i) The sectors 

 of the arculus are not stalked in either wing. (2) The sub-triangular 

 space consists of three areoles. (3) A short sector, which may be called 

 the apical sector, arising beneath the stigma from the principal sector and 

 extending to the apex in both wings, in this species arises under the proxi- 

 mal fourth of the stigma. This apical sector develops from a tracheal 

 branch, is very constant in position, and may readily be recognized even 

 when somewhat irregular if taken in connection with another which 



may be called the sub-apical sector which (in Libellulidfe) lies just pos- 

 terior to it, parallel with it, and separated from it, except at the proximal 

 end, by a single row of areolets. Hagen, describing Libellula deplanata, 

 Rambur, in 1861 (Syn. Neur. N. Amer., p. 154), questioned whether it 

 belonged to the genus. The nymph supplies an emphatic negative, which 

 the venation and doubtless other adult characters corroborate, and which 

 is equally applicable to the more recent subdivision of the genus. I 

 therefore propose a new genus Ladona with L.exusta, Say ( = L deplanata, 

 Ramb.), for its type. And for this interesting and locally common species, 

 which ranges from Florida and Maine to the Columbian River basin, 

 because of its very distinctive white humeral stripes, I would suggest the 

 common name, " the Corporal," 



