Sphenophorus placidus Schoenherr, 1838
| Observations upon a collection of insects made in the vicinity of New Orleans, Louisiana, during the years 1882 and 1883 Shufeldt R W. (1884) Proceedings of the United States National Museum, Washington 7: 331-338 | |
| On the species of Sphenophorus hitherto considered as placidus Say F H Chittenden (1904) Proceedings of the Entomological Society of Washington 6: 130-137 |