ee 
AGRION. 
101 
Key to Genera known (or likely) to occur in Mexico and Central America. 
§ 1. Arculus at the second antecubital or but slightly beyond (i. e. by less than 
the length of the upper limb of the arculus itself). 
1. Nodal sector on the hind wings arising at or near to the fourth postcubital 
or more remote (except in Enallagma basidens, which is like 2). 
A. Costal side of the pterostigma on the hind wings (and often also on the 
front wings) usually shorter than the proximal or distal sides*. 
Superior and inferior sectors of the triangle on the front wings 
reaching to the levels of the origin of the ultra-nodal and nodal sectors 
respectively or beyond. 
B. Venation of the front and hind wings in the male similar; female 
with a ventral apical spme on segment8 . .. . 
BB. Venation of the tips of the front and hind wings of the male 
dissimilar ; female with no ventral apical spine on segment 8 
AA. Costal side of the pterostigma on all the wings usually longer than the 
proximal or distal sides. Venation and pterostigmata of front and 
hind wings similar in both sexes. 
C. Inferior sector of the triangle arising at least as far in front of the 
submedian cross-vein as the latter is long +. Pale postocular spots 
on a dark ground present. Abdomen chiefly black, or blue and 
black. Females with an apical ventral spine on segment 8. Males 
with the hind margin of segment 10 more or less emarginate, but 
not usually elevated into a distinct tubercle or process . 
CC. Inferior sector of the triangle arising at or slightly beyond the 
submedian cross-vein. Pale postocular spots as above. Colours 
black with blue or green. Females spined as above. Males with 
the hind margin of segment 10 more or less elevated into a process 
or plate which is excised or bifid at tip . . . . wee 
CCC. Inferior sector of the triangle arising at the submedian cross-vein 
or at a less distance in front than the latter is long. No pale post- 
ocular spots on a dark ground. Abdomen of the males chiefly red, 
of the females red or dark metallic-green, -brown, or -black. 
Females not spined as above, their genital valves not reaching 
beyond the terminal abdominal appendages. Superior appendages 
of the males not as stated below for the next genus . Le 
CCCC. Inferior sector of the triangle as above stated for Telebasis. No 
pale postocular spots on a dark ground, or, if present, confluent with 
HESPERAGRION. 
ANISAGRION. 
ENALLAGMA. 
ACANTHAGRION. 
TELEBASIS. 
* Except in Ansagrion truncatipenne, the proximal and distal sides of whose pterostigma on the hind 
wings are almost at right angles to the costa, instead of forming oblique angles therewith, as in most 
Agrionine. 
+ Exceptions occur in possibly the majority of individuals of Enallagma antennatum, Say (fischeri, Kclicott), 
and E. «divagans, Selys, of the United States, in which this sector is as above stated for Telebasis. 
