[I'm adding this image and the next in response to Ron's comment under the 1st image in this series.]

The key to Allograpta on page 15 of Fluke (1942) separates A. obliqua and A. exotica at couplet 7, which reads:

    7a. Pteropleura black on lowest two-thirds or more.....11 (leading to A. exotica)
    7b. A yellow band extends over the upper part of the sternopleura, lower part of the pteropleura, and onto the hypopleura....8 (leading to A. obliqua)

I've inset a figure from pg. 32 of Williston's 1908 "Manual of North American Diptera" illustrating the (old) terms used above by Fluke. To my eye, the yellow band beginning on the sternopleura (i.e. behind the middle-leg tibia in my image) continues uninterrupted across the middle third of the pteropleura and on to the hypopleura (except for a thin black line at the suture between the sternopleura and pteropleura). So that would take this specimen to A. obliqua. (A. obliqua is also the better fit for the markings on the tergites shown in the last image in this series.)

Newer treatments of Diptera use the more modern terms below for lateral sclerites of the (meso)thorax:
   1) "anepisternum" (= old mesopleuron);
   2) "katepisternum" (= old sternopleuron);
   3) "epimeron" (= upper two-thirds of the old pteropleuron), which consists of...
       a) "anepimeron" (= larger, upper portion of the old pteropleuron);
       b) "katepimeron" (= smaller, middle portion of the old pteropleuron); and
   4) "meron" (= lower third of the old pteropleuron).
The correspondences of new and old terminology given above are based on comparison of Williston's diagram for Syrphus in the inset above with various diagrams in the Manual of Neartic Diptera (namely Figs. 2.64-2.66 on pg 24-26 of Vol. 1(1), and figure 64 on pg. 730 of Vol. 2(2)). See also the diagram at this link (scroll down a screen to "Fig. 6").

For instance, the (1992) treatment by Vockeroth(3) describes A. obliqua as having:

    "Pleura black with most of upper half, including anterior anepisternum and katepimeron, bright yellow."

And Vockeroth(3) adds that:

   "The abdominal markings [of A. exotica] are similar to those of A. obliqua, but the anterior anepisternum and the katepisternum are black rather than yellow."

This is in accord with Martin's reference post that compares these two species. Note that in Martin's images of A. exotica, the yellow band at the base of the pleura has a conspicuous "break" at the posterior end of the katepisternum (and into the katepimeron), whereas that yellow band is more or less continuous in Martins's image of A. obliqua and in the image of my specimen (except for the hair-thin black suture between the "sternopleuron" and the "pteropleuron"). One of Martin's A. exotica images appears in the post below, again, note that the yellow band on the lower pleura has a break at the posterior end of the katepisternum and into the katepimeron:



So, in summary, all the above seems to me to point pretty clearly to A. obliqua here, rather than A. exotica. But maybe I'm wrong...hopefully Martin will view this at some point and correct or confirm my interpretations of all these technical terms and characters.

One last comment...I think using the "black stripe on the face" character alone to decide on A. exotica may be problematic. Vockeroth(3) states that female A. obliqua usually also have a median pale to dark brown stripe...and one person's "dark brown" may sometimes be hard to distinguish from another person's "black". Also, note the the "face" is the region below the antenna and above the clypeus, whereas the "frons" is the area above the antenna up to the vertex (i.e. the "forehead"). For instance, the frons in this image has a median black stripe, while I'd say the the stripe on the face is brown there.