|Ophiogomphus susbehcha in Maryland
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Udate 9- April-2018
The population of Ophiogomphus susbehcha has resumed its low-level numbers along the Potomac River after
the high emergence numbers of 2012-2013 In 2014 two casts skins and 2 adults were found (April 27 & April
28). In 2015 two adults were found (April 29 & May 4), In 2016 only 2 cast skins were located (April 17) and in
2017 no cast skins or adults were recorded. The search for this species each year has been significant. Both
myself and several other people have helped locate this hard to find species.
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 (Wisconsin) specimens.
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 this species.
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 similar.
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 Snaketail.
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