I thought that documenting this species would be easy, since it's quite common, however, once I started digging in, it turned into quite a taxonomic rabbit hole that is not quite fully resolved (from a bibliographic citation trail) in my mind.
First issue, GBIF, via the Catalogue of Life, lists the citation for the species as:
Say, T. (1832) In New species of North American insects found by Joseph Barabino, chiefly in Louisiana. New Harmony, Indiana. 1–16 pp. [1831]
I wasn't able to find a copy of this item on BHL, but HathiTrust did have a copy (see here). I went through this sixteen pages way too many times and found no mention of Leptoglossus oppositus (or Anisoscelis oppositus as first named by Say).
Finally, I went to the collected works of Say (on BHL):
Say, Thomas, & LeConte, John Lawrence. (1891). The complete writings of Thomas Say on the entomology of North America (Vol. 1, p. 327). A. E. Foote. https://www.biodiversitylibrary.org/page/24631474
And went page by page through the 1830-1832 publications. As I expected, I didn't find anything in New species of North American insects found by Joseph Barabino, chiefly in Louisiana. But, I did find A. oppositus described in:
Say, Thomas. 1831 December. Descriptions of new species of HETEROPTEROUS HEMIPTERA of North America. New Harmony, Indiana. (BHL page link -- see page image below).
So, it looks like GBIF and the Catalogue of Life need to do a bit of cleanup on their citations!
From Wikipedia: Leptoglossus oppositus a species of leaf-footed bug (family Coreidae) found in North America. It resembles Leptoglossus fulvicornis but can be distinguished by the deeper scallops in the leaf-like feature of the hind tibia and the addition of three white spots across the hemelytra. This species is widely dispersed from New York to Florida and as far west as Iowa and Minnesota, as well as the southwest regions of the United States into Mexico.
HISTORIC DOCUMENTATION
Leptoglossus oppositus was first described by Thomas Say in 1831 (December) (as Anisoscelis oppositus):
3. A. oppositus. — Reddish-brown; hemelytra with a white point in the middle of the corium; antennae rufous; head trilineated; posterior tibiae dilated and sinuated.
Inhabits Indiana.
This is very closely allied to albicinctus nob., but is uniform in its differential characters. It may be known by the small white point of the hemelytra.
Say, Thomas. 1831 December. Descriptions of new species of HETEROPTEROUS HEMIPTERA of North America. New Harmony, Indiana. Reprinted in The complete writings of Thomas Say on the entomology of North America (Vol. 1, p. 327). A. E. Foote. https://www.biodiversitylibrary.org/page/24631474.