In most of New Jersey the Common Baskettail (Epitheca cynosura)
is the default species, although it has yet to be reported in the
southernmost counties. Slender Baskettail (Epitheca costalis),
formerly called Stripe-winged Baskettail, has been reported from
several counties and should be looked for throughout the state.
Until recently, little was known about the differences between
these species and even now in-hand ID is difficult at best. Field ID
is even harder and may be impossible with the current state of
knowledge. The exact relationship of these species and others within
the Baskettail complex is still under review and the ID characters
are poorly understood.
The marks mentioned in the following table are drawn mainly from
Abbott's Dragonflies and Damselflies of Texas but also from scans
supplied by Nick Donnelly: (Any errors of interpretation are mine,
not theirs)
Common Baskettail (E. cynosura)
|
Slender Baskettail (E. costalis)
|
|
Abdomen often spindle shaped, widest at S5
|
Abdomen narrow behind S3
|
|
S3 not constricted, rather parallel sided
|
S3 strongly constricted with concave sides |
|
male cerci short, usually divergent in dorsal view
|
male cerci over 3.4mm, usually nearly parallel |
|
cerci with lateral keel well developed, ventral
angle thinner and more angled>
|
cerci with poorly developed lateral keel and more
rounded ventral angle
|
|
female cerci less than 2.25mm>
|
female cerci longer than S9+S10
|
|
hindwing with variable basal spot
|
hindwing basal spot limited or absent
|
Note that almost all of these marks are
tendencies. Field ID is not going to be very reliable,
especially when you must consider Spiny and Beaverpond
Baskettail. To some degree the marks mentioned above may pertain
to Texas specimens. To my eye, our Common Baskettails seem to
have rather parallel-sided abdomens, with Beaverpond exhibiting
a "spindle" shape.
Following are two sets of scans from Nick Donnelly which show
the differences in S3 and the cerci. The second set includes
Dot-winged Baskettail, which doesn't occur in New Jersey.