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This Codatractus sp. was photographed at the Mission RV Park Hedge on August 8th 2004:

There was some discussion on whether it could be identified to species; Mike Overton suggested that C. alcaeus and C. carlos are the two that are likely to be
confused, while hyster, bryaxis, melon and sallyae are also somewhat similar to each other. I think that all records of Codatractus from the LRGV have been claimed to be alcaeus, but there is no confirmed specimen (please correct me if I'm wrong.) I have no experience of this genus outside this individual, but there are a series of eight specimens (dorsal and ventral views) each of alcaeus and carlos available at this website that offer a possible means of separating these two taxa.
On the two images below I have circled the areas that I feel may be useful:-
A: the size of the FW apical spots seems consistently different between all eight alcaeus and carlos, in that the former has four large spots that connect with each other while the latter has three small spots with a gap between the inner two and outermost one.
B: each taxon has a row of four large submedian pale blocks on the FW; on alcaeus the lowermost block has its basal edge aligned below the third block, creating overlap; on carlos the lowermost block has its basal edge beyond the outer limit of the third block, thus having no overlap.
C: the difference here is hard to put into words, but fairly easy to see:- basically on alcaeus the twin dark marks coalesce in the central portion then taper out in a fairly straight line well away from the dark block on the extreme right of "C"; on carlos the twin marks never seen to coalesce, instead the outer one either disappears, or continues as a ghost paralleling the inner dark mark, which stays the same thickness throughout and tends to have a more sudden downturn away from the dark block at the extreme right, with a smaller or non-existant pale gap between them.
D: this is less clear, but on alcaeus the two dark blocks at the lower-right of "D" tend to touch or overlap, while on carlos these usually don't touch

- I realise that this is a small sample, but the differences in A, B, and C seem quite clear and consistent - and the Mission bug fits alcaeus on all counts.... I'd appreciate feedback - thanks.