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The genus Trachelas comprises a number of remarkably similar-appearing species. While the most widely reported member of the genus in NC is tranquillus, positive species determination requires microscopic examination of the genitalia.
In 2020, a population of Trachelas sp. was found in downtown Smithfield (near the center of Johnston County) and originally thought to be tranquillus. Subsequent microscopic examination of the male palpi indicated, however, that they were clearly of some other species, and, based on those palpi, most likely T. volutus, a species having been reported from TX, LA, FL, and GA.
Because the external appearance of the epigyna of different trachelid spiders can be extremely difficult to differentiate, an assumption was made that because all the male specimens collected appeared to be volutus, the local females were that same species.
In 2023, seeking to provide better photos of “volutus” genitalia, the epigyna of 7 female specimens were dissected, cleared in lactic acid and examined: Without exception, they were clearly not those of tranquillus—but neither did they resemble those of volutus!
Instead, the only reported North American species having both male and genitalia matching those of the Smithfield spiders is T. mexicanus, a species nominally ranging from western Mexico through Texas to northern Utah.
Thus, in consideration of this morphological evidence, the large population of people from the southwestern States and Central American countries now living in and around Smithfield NC, the well known synanthropic behavior of Trachelas spp, and the ease with which humans can inadvertently transport such arthropod species, it seems not only possible, but likely, that T. mexicanus has made its way here: Accordingly, locally collected specimens have been labeled as such.
We have retained the possibility that the closely related volutus could still very easily appear—or already be—in NC, and we shall be very interested in monitoring any further movements.
All the examined specimens have been retained, and further sampling will be continued.
--dbz April 2023 | 
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