The dark AM band being curved and not touching the inner margin, as well as the orange border along the bottom of that band indicates erechtea.

I'm a bit confused now gentlemen.

Should I just move this one to the Caenurgina level?? I'm not as seasoned a lep person as you two and am uncertain what to do with this particular photo.
Nina

Jason, I would say that the characters that you have pointed out are better expressed in C. erechtea than in C. crassiuscula but they definitely are pretty variable in both species and do not work in all specimens. I have seen specimens of C. crassiuscula with curved to some degree AM line and with yellowish outline on the inner side and I have seen specimens of C. erechtea with almost straight AM line and with no outline. Other characters of wings pattern and size also don't work 100%. The only characters I know that allow separate these two species clearly are genitalia.

I agree with you Jan that dissection is the best method to distinguish the two. In my experience, erechtea is the primary one of the two to exhibit the characteristics listed, so given only a photo to go by I gave my best judgment. But what would you say is the best placement for this one? I don't see any reason for it to be moved to crassiuscula since even if it is one, it isn't the more "typical" crassiuscula and cannot be ultimately confirmed as such. I was thinking it was best to leave it at erechtea, especially now that our comments are here to notate the ID difficulties. Of course, we could always move it to genus level. Your thoughts?

Sorry for a delay to answer. Here are my reasons to defend placement of this specimen in C. crassiuscula.
1. There are two darker areas in forewing's pattern of Caenurgina: one along the AM line on the outer side of the line and another one along the PM line on the inner side of the line. C. erechtea show sexual dimorphism in expression of these characters. In males these dark patches usually are contrasting very well from the forewing's ground color, have well defined edges and are clearly separated one from another. In females of C. erechtea dark patches are purely developed and forewings look more or less unicolorous without contrasting elements. In C. crassiuscula males and females have these dark patches similarly developed, edges of these patches are usually obscured and blurred (except for the AM line), and dark patches usually merge near the inner margin of the forewing. In this specimen these two dark patches have blurred edges and are merging near the inner edge of the forewing.
2. This specimen has the ST line almost completely reduced except for few dark blotches near the costa. Specimens with such condition of the ST line are more common in C. crassiuscula than in C. erechtea.
3. The shape of the AM line. The AM line is clearly waving in this specimen. Such condition is common in C. crassiuscula. In C. erechtea AM line is usually less waving, often straight or evenly arching.
Every of mentioned characters is varying more or less in both species and can’t be used for precise separation of C. erechtea and C. crassiuscula. However, combination of several characters may allow identifying with high possibility of correct ID.

I see what you're saying. The dark areas are in fact merging near the inner margin. I copied the photo and played with darkening the midtones and adjusting contrast and it became quite apparent. My apologies for not seeing that.

Now the AM line got me too. I'm used to seeing crassiuscula with fairly straight AM lines reaching to about one third the distance of the inner margin from the base, whereas the erechtea AM line usually curves and can have some wave to it. And the yellow-orange border through me off too.

I appreciate the help and explanation. I've only pulled tails on a few Caenurgina (very small genitalia for my experience). Perhaps I've relied a bit too much on a few select external wing characteristics. :)

Thanks again Jan.

(And my apologies Nina, for adding any confusion)

so, what's the final call on this one then? Guide placement in erechta or crassiuscula?

no need to apologize, this has been quite educational for me. 8:)
Nina

I defer to Jan's judgment on this one. It is most likely a crassiuscula, and would be fine placed there.

back to erechta then... unless anyone thinks it's better in the genus level; if that's the case, just post a reply and we can discuss again.
Nina