480 NEW YORK STATE MUSEUM 



h Sectors of the arculus (veins M1-3 and M4 ) distinctly separate at tbeir 

 departure from the arculus; anal loop elongate, but not distinctly foot- 

 shaped, the toe part being little or not at all developed; the last antenodal 

 cross vein extending from the costal to the radial veins (except in D. 

 lintneri, in which it generally extends only from the costal to the 

 subcostal) ; colors often metallic blue or green on thorax and abdomen 



Cordulinae p. 484 



1)1) The sectors of the arculus in close apposition or completely fused for a little 



way beyond the arculus; anal loop generally distinctly foot-shaped, with 



well developed *'toe"; the last antenodal cross vein often discontinuous 



at the subcostal vein Libellulinae p. 506 



a Head with a prominent pyramidal frontal horn ; abdomen flat, and almost 

 circular in outline as seen from above ; legs long, giving a spiderlike 

 aspect to these big nymphs; 10th abdominal segment well exposed, not 

 telescoped in the apex of the ninth segment; teeth on the lateral lobes of 



the labium with deep incisions between them Macromlinae 



aa Head without pyramidal frontal horn ; abdomen less flattened, more elongate ; 

 teeth on the lateral lobes of the labium much wider than high. 



1) Lateral appendage^ of the abdomen more than half as long as the inferiors ; 

 hind femora longer than the head is wide; when the lateral spines are 

 long (fig. 19s), then there is a full series of big, cultriform dorsal hooks on 



the abdomen Cordulinae 



1)1) Lateral abdominal appendages generally less than half the length of the 

 inferiors ; hind femora generally as long as the head is wide ; often when 

 the lateral spines of the abdomen are long the dorsal hooks are wanting or 

 reduced Libellulinae 



Subfamily ivEACRONiiiNAE^ 



A small group of large species, more distinct than any other group 

 v^ithin the family. The imagos are bulky and not very graceful, hairy 

 and not strikingly beautiful in their coloration, but their flight is strong 

 and well sustained : they glide through the air with the fearless abandon 

 of masters of a situation. 



The nymphs are quite unique in the family in the possession of a flat 

 abdomen, almost circular in outline, recalling that of Hagenius, 

 though less flat and circular than that, and an erect pyramidal horn on 

 the front of the head ; in this last character, they are unique among all 

 Odonata. They lie flat on the bottom where there is little mud, or 

 oftener, on some nearly bare ledge in the border of a stream, with their 

 thin legs radiately arranged, and the body almost completely covered 

 with silt. Thus they await their prey and seize it when it approaches. 

 They are all an undetermined number of years reaching maturity. 



Our two genera may be separated as follows : 



