18 DRAGONFLIES OF NORTH AMERICA 
there is a quadrangle (q); and it is the equivalent of both triangle (f) 
and supertriangle (s) of the dragonfly wing, as a comparison of the 
accompanying figures will show clearly. There is also a subquadrangle ; 
and these same figures will show that it is the equivalent of both 
subtriangle (¢’) of the dragonflies and the space before that cell extend- 
ing baseward to the anal crossing (Ac). 
Such are the principal features of dragonfly wing venation. The 
lesser details will be taken up in the discussion of the groups to which 
they pertain. 
Genitalia.—The abdomen of a dragonfly is composed of ten distinct 
segments and a rudiment of an eleventh that is combined with the 
terminal appendages. The first and tenth segments are shorter than 
the others. The second and third are swol- 
len to form a more or less spindle-shaped 
enlargement of the base of the abdomen. In 
the male dragonfly they bear on the ventral 
side the unique copulatory organs that are a 
distinguishing characteristic of this order. 
Since the ultimate criteria of species are 
often to be found in the form of the acces- 
sory genital apparatus, it is important to 
know these parts. They differ so much in 
the two groups that the suborders are better 
considered separately; but there are these 
things in common: 
WE MS (1) The males have appendages at the 
Fic. 7. Diagram of copu- end of the abdomen that are forceps-like in 
latory position, Aeschna con- action, and that are used for seizing and 
ara. adher Cay cte. holding the female. He grasps her by the top 
of the head (Anisoptera) or pro- thorax (Zygoptera) and leads her 
about in flight. The two thus speed about together in tandem, or settle 
together, still in tandem on a stem. 
(2) The males have, also, in a cleft on the ventral side of the swollen 
second abdominal segment, paired hamules for grasping, and a penis 
for sperm transference. Previous to copulation the sperm must be 
transferred from the spermaries, whose ducts open on the ventral side 
of the ninth segment to a cavity in the tip of the penis. This is done 
by bending the abdomen downward and forward, bringing the two 
orifices into apposition. 
(3) The female is not so different from females of other orders. 
She has a genital opening at the apex of the eighth abdominal segment 

