330 DRAGONFLIES OF NORTH AMERICA 
mid-dorsal black thoracic stripe .68-.7 mm., of the pale antehumeral stripe 
.85-.42 mm., of the black humeral stripe .24-.85 mm. Third lateral suture with 
a blackish-brown stripe, or line, for the uppermost fourth to three-fourths of 
its distance. Dorsum of abdominal segments 1-8 and 10 metallic black. Segment 
9 entirely yellow. 
Female. Color sometimes blue and black. Lateral end of the mesostigmal 
plate black, the humeral stripe touching the lower end. Prothoracic pits large. 
Widths of the black thoracic mid-dorsal stripe .63—.7 mm, of the pale antehumeral 
.35-.42 mm., of the dark humeral .28-.42 mm. Black of the dorsum of segment 9 
usually narrowed posteriorly. 
322. Enallagma vesperum Calvert 
Calv. ’19, p. 380: Garm. ’27, p. 64. 
Length 30-34 mm. Expanse 34-42 mm. U. S. east of Miss. R. 
A species that is found abundantly along the shores of the Great Lakes, but 
not at all restricted to them. Color, orange or yellow and black. Face yellow. 
Postclypeus entirely black or with two median spots and margins of yellow. 
Pale transverse frontal band sometimes attaining the pale spot immediately 
anterior to the median ocellus, and indundating the black of the superior surface 
more deeply than in £. pollutum. Postocular spots connected with each other, 
but not confluent with the pale of the rear of the head. First two segments of 
the antennae pale. Vertex black, except for two pale ocellar spots. Anterior and 
posterior lobes of the prothorax mostly yellow; middle lobe usually predomi- 
nantly black on the dorsum, a spot on each side, a pair of median spots or lines, 
and the sides inferiorly yellow. Thorax with the pale antehumeral stripe wider 
than the dark humeral. Width of black mid-dorsal thoracic stripe .28-.67 mm., 
of the pale antehumeral stripe .35-.7 mm., of the dark humeral stripe, from a 
mere line to .28 mm. Third lateral suture with a black stripe on its uppermost 
fourth or fifth only. Abdomen with the dorsum of 1-8 and 10 entirely metallic 
black, reduced somewhat on 10. 9 entirely blue. 
Female: Lateral margins of the mesostigmal plate not margined with the 
black of the humeral stripe, but having a black spot on itself. Postocular spots 
as in the male, not connected with the pale color of the rear of the head. Width 
of black thoracic mid-dorsal stripe .33-.63 mm., of the pale antehumeral stripe 
.42-.63 mm., of the black humeral, from a mere line to .14 mm. Dorsum of 9 
black, not reaching the apical margin. 
The £#. pollutum of most writers on northern species of Enallagma is 
synonymous with EF. vesperum. The true pollutum is entirely southern. 
323. Enallagma dubium Root 
Root ’24, p. 317: Byers ’27, p. 388. 
Length 26 mm. Expanse 28 mm. Ga. and Fla. 
A small very dark Enallagma collected in cypress swamps. Color, metallic 
black and yellow-red. Male: Head pale beneath. Postclypeus black. Frons with 
the pale transverse anterior band reaching the basis of the antennae. Antennae 
entirely black. Remainder of frons and the vertex black (no pale markings about 
