It has been a banner year for Ophiogomphus susbehcha. Between April 24th and May
12th, 31 cast skins were found and 15 adults were identified (7 kept and 8 netted and
released). The range of the population is now known from 16 km of the Potomac River
in Frederick County, Maryland.
Steve Roble, Oliver Flint and I met at the Smithsonian to compare specimens of the
Chesapeake Snaketail from the Potomac River (Maryland) and James River (Virginia)
along with the Ophiogomphus susbehcha type specimens in the museum. No
distinctive consistent morphological characters could be found between them except for
the larger size of the type specimens. It is our thought that the Chesapeake Snaketails
are Ophiogomphus susbehcha. Whether the Chesapeake Snaketail warrants a new
subspecies level will be decided after the DNA of the Potomac River (Maryland) and
James River (Virginia) specimens are compared with that of the Saint Croix River
Fifteen additional cast skins of the Chesapeake Snaketail were found on the Potomac
River near Point of Rocks in 2012 (April 8, 12 & 15) plus one mature male on April 25.
This brings the total of this unnamed species recorded from the Potomac River to
nineteen (17 cast skins & 2 adult males).
Two cast skins of what is now referred to as the Chesapeake Snaketail were found on
the Potomac River near Point of Rocks on April 31, 2010. These were likely old skins
at least a couple of days old if not more. This brings the total of this unnamed species
recorded from the Potomac River to three (2 cast skins & 1 adult male).
It is no longer appropriate to call this dragonfly the Potomac Snaketail. Over the last
couple of years this species has been found on the James River in Virginia. Cast skins,
males and females have been collected. In addition, a historical record, from the
Susquehanna River in Pennsylvania, that was initially mis-identified, also appears to be
No additional specimens have been found on the Potomac River or in Maryland.
The taxonomic status of this species which is clearly related (if not a subspecies of)
Ophiogomphus susbehcha has yet to be worked out.
Original Posting (2006)
The Potomac Snaketail (Ophiogomphus sp.) is currently known only from a single male
collected on 20-April-2002, at 11:10 AM, near the north edge of the C&O Canal NHP
line and the railroad property near Point of Rocks, Frederick County, Maryland. There
are no additional specimens (or visual sightings) of this dragonfly despite extensive
attempts during the 2003-2004 field seasons. It was photographed in the field to
record actual colors and later taken to the Smithsonian Institute to have it
photographed using a montage imaging camera. The male was still soft (not mature)
when captured thus indicating that it had recently emerged from the Potomac River. It
was allowed to harden for a day before preserving.
The following is a brief description of the Potomac Snaketail. The specimen measured:
Length = 46mm, Abdomen = 32 mm, HW = 26 mm. The left hind wing has an anal loop
of 2 cells with a short appendage (vein) while the right HW does not have a distinct anal
loop. The labrum and anticlypeus are white around the edges and muffled gray
internally. The postclypeus is greenish except for upper lateral-yellow edges, which
bleed over onto the otherwise greenish frons. Occiput is bright yellow with a long black
row of hairs along the dorsal ridge. The thorax has the dorsal carina prominent --
highest near middle with a black tipped ante-ala-crest on an otherwise reddish brown
dorsal carina. The mid-dorsal stripe is reddish-brown and prominent; widest anteriorly.
The humeral and antehumeral strips are barely separated but never touch. The
antehumeral strip is not complete at the dorsal end. The humeral strip is complete. A
prominent interpleural stripe extends dorsally to, and slightly curves around the
spiracle. The metapleural stripe is prominent and complete. The thoracic stripes are
reddish-brown. The tarsus are black. The tibia are black with no yellow ridge on any
tibia. Femora about 50/50 black (apically and dorsal) and yellowish brown (mostly
apically and ventrally). The auricle is yellow. The dorsums of A3-8 have diminishing
basal yellow triangles with a short dorsal yellow line continuing for a short distance.
The yellow spot on the dorsum of A9 is square shape. A10 is all yellow. A3-8 are black
on the dorsal-lateral 2/3 of each segment as seen from a lateral view. The abdominal
appendages are dull, light yellowish/brown, and match the description of
Ophiogomphus susbehcha in Vogt and Smith, (1993). The epiproct is much longer
than the cerci. The epiproct has a conspicuous dorsobasal protuberance which is not
present in other species belonging to the “mainensis” group of eastern North American
ophiogomphids. This dragonfly keys to Ophiogomphus susbehcha (St. Croix Snaketail)
in existing keys.
The Potomac Snaketail was compared to the holotype male and three paratype males
of O. susbehcha in the National Collection at the Smithsonian. The visual differences in
size between the Potomac Snaketail and the holotype male and the three paratype
males of O. susbehcha was significant, much more so than the 50 to 52mm lengths of
the O. susbehcha species and the 46mm length of the Potomac Snaketail would
suggest. Clearly the Potomac specimen is much smaller and less massive than the St.
Croix Snaketail’s holotype and paratypes. In general however, the Potomac Snaketail
was structurally closer to the four specimens of O. susbehcha in the National Collection
than any other species of Ophiogomphus.
The only differences in body markings were very slight and could easily be explained
because the Potomac Snaketail specimen was still young when captured when
compared to the completely mature O. susbehcha specimens. Specifically, the Potomac
Snaketail when compared to the O. susbehcha had slightly lighter colored eyes; upper
2/3 of the femurs were lighter in color; and the dorsum of A10 more yellow towards the
anterior base. But again, the overall color/markings on the abdomen and thorax were
The secondary genitalia were indistinguishable from O. susbehcha. Also the superior
appendages were very close. The large dorsal protuberance just anterior to the lateral
projections on the epiproct, which sets O. susbehcha apart from other Ophiogomphus
species, was similar. The lateral projections of the epiproct were distinctly more
pronounced on the Potomac specimen than on the O. susbehcha types while the
sharply up-turned ends of the epiproct were identical. The Potomac specimen did differ
from the types in that between the upturned end and the lateral projections of the
epiproct an additional bump (small protuberance) was present. This could be seen on
the type specimens but it was not as large or as distinct as on the Potomac Snaketail.
This protuberance was reminiscent of what is seen on some O. mainensis. The cerci
were identical in shape and length to O. susbehcha except that the distribution of the
small black pimples were more irregular (not so much in a line) on the Potomac
All of the species of Ophiogomphus in the National collection were carefully compared
to the Potomac Snaketail to make sure that nothing was missed. Special effort was
spent comparing the various species cerci and epiproct with that of the Potomac
Snaketail. Ophiogomphus susbehcha was the only species that came close to
matching the Potomac Snaketail in this respect. Particular attention to specimens of O.
mainensis and the two subspecies of O. incurvatus were undertaken. The possibility
that the Potomac Snaketail was one of these two species in which the cerci were
deformed (not fully extended) had been brought to my attention. However, the O.
mainensis and O. incurvatus specimens never showed the large epiproct dorsal
protuberance anterior to the lateral projections that was so obvious on the Potomac
specimen and the O. susbehcha types. In addition, there was no indication of deformity
with the abdominal appendages on the Potomac Snaketail specimen.
Because the Potomac specimen is distinctly smaller in size, with a much earlier
emergence date, a long distance from St. Crox river drainage, and has differences in
the abdominal appendages from O. susbehcha my conclusion is that this is most likely
a sister species or at least a distinct new subspecies of O. susbehcha.
|Live -- top of abdomen tip
|Montage image -- Side of
|Montage image -- top of
Montage image -- hamules
Base of Hindwing