162 
DRAGONFLIES OF NORTH AMERICA 
Anal loop somewhat foot-shaped but with little development of 
the toe; males with auricles on the sides of the second abdominal 
segment, and with the adjacent inner margin of the hind wing 
NOLGHEG! 4. in cece oe ere ee ee Corduliinae, p. 171 
Anal loop (in ours) generally distinctly foot-shaped with a well 
developed toe; males without auricles on 2, and inner margin 
Of hind ‘wing rounded: .6.. ote eee Libellulinae, p. 201 
Nymphs 
Head with a prominent frontal horn; abdomen flat and subcircular; 
legs very long; teeth on lateral lobe of labium with very deep 
incisions between them................. Macromiinae, p. 163 
Head with no prominent frontal horn; abdomen more elongate and 
less depressed; teeth on lateral lobes of labium with only shallow 
incisions betweem theme (262 Py... 29. ee ae 2. 
Hind femora longer than the head is wide; when the lateral spines 
are long there is a full series of big donee hooks on the abdomen 
DEAR, OAS OE rat, ee ee Ean Corduliinae, p. 171 
Hind femora not longer than the head is wide; when lateral spines 
are long there is generally no full series of big dorsal hooks on the 
abdominal segments: ... o. Mg wa. os bon Libellulinae*, p. 203 
* These last alternatives are of uncertain application. When in doubt try 
both routes. 

Fia. 32a. Sexual differences in color pattern in Plathemis lydia. 
