mi 
No. 4.— Illustrations of Odonata: Argia. By HERMANN A. 
Hacen. With a list and bibliography of the species. By 
Puitip P. CaLveErt.! 
Tue illustrations herewith presented require some words of explana- 
tion. De Selys and Hagen intended publishing a Monograph of the 
Agrionine, following a Synopsis of this subfamily, as they had for the 
Calopteryginze and the Gomphinze. The Synopsis appeared in instal- 
ments from 1860 to 1877. Hagen made drawings for the Monograph 
which was never published, if indeed it ever was written. These, before 
his death, were given to his friend and successor in the Museum of 
Comparative Zodlogy, Mr. Samuel Henshaw. Some of these drawings 
— those referring to the “grande genre Argia”” — have recently been 
lent to the present writer to be used in the study of material for the 
Odonate part of the Biologia Centrali-Americana. So useful have they 
thus proved, so desirable does it seem that others should have the 
opportunity of using them, that they are here published. 
If justification were needed for this proceeding, it may be found in 
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these words of De Selys from the Synopsis of Argia, page 381 : 
“De grandes difficultés se présentent pour donner les diagnoses des quarante- 
six espéces américaines, dont plusieurs sont tres-voisines les unes aux autres. 
Les appendices anals des males et les lames du devant du thorax des femelles 
fournissent, il est vrai, pour la plupart, des caractéres positifs ; mais ils eussent 
rendu les diagnoses trés-longues, et ces organes ne pouvent étre bien vus 
qu’avec un certain grossissement, j'ai cherché dans les diagnoses de ce Synop- 
sis, & me passer de ces caractéres, qui seront réservés pour une monographie 
spéciale.” 
As to the figures themselves, the original sheets on which they were 
made bear the signature “ H. Hagen del. 1864.” As far as known, they 
were executed without the aid of a camera lucida. It may be admitted 
that they are not in all cases perfectly satisfactory, due partly to the 
fact that the structures they depict were not sufficiently spread apart 
to be clearly seen, as in Plate 2, Figs. 6a, 14a. It must also be borne 
1 The second-named author is responsible for the entire text of this article. 
