It seems that nearly every author who has considered these two species
has compared them. Considering general appearances they are much alike
but can be separated easily by several details and as I have good
material of both sexes of the two species before me, I thought it
might be of consequence to consider in a comparative way some of their
characteristics.
The occiput in both sexes of _villosipes_ bears a prominent tooth at
the middle of its upper edge. This tooth varies some in different
specimens, it ends above in a single point or it may be widened and end
above in three or more points. In _furcifer_ there is no tooth on the
occiput in either sex.
The vulvar scales are very different, in _villosipes_ the part may
be said to be triangular with the free sides curved and the apical
part divided for about half the length of the scale. In _furcifer_
its basal part is similar but the apical part is produced, giving
quite a different form. In the former species the scale is about
one-third as long as the ninth segment, while in the latter it is about
three-eighths as long as that segment.
The abdominal appendages of the male are different. From dorsal view
those of _furcifer_ are rectangular with the inner distal angle very
much produced inward and backward; in _villosipes_ they are wide at
base, oblong, with the outer distal part broadly rounded and the
corresponding inner part produced directly backward. The hamules are
characteristic and may be explained best by reference to the figures.
The two species are colored much alike but _furcifer_ is darker.
The tenth abdominal segment may be said to be yellow in both but in
_furcifer_ the sides of the segment are dark, oftentimes black.
They agree in habits, both preferring to fly over stagnant water where
the males come to rest on floating objects or on the ground at the
water’s edge. I have observed the female of _furcifer_ ovipositing in
stagnant water among lily pads and other aquatic plants. Her flight is
slow while thus engaged, and her actions more like a _Libellula_ than
the usual _Gomphus_.