I found 2 different sites with pictures identical to this moth with 2 different ID's. The first one is Adhemarius eurysthenes,
http://www.americaninsects.net/lep/adhemarius-eurysthenes.html
The second one is Adhemarius ypsilon,
http://pick4.pick.uga.edu/mp/20p?see=I_CAM12120&res=640
I think A. ypsilon is the better choice, since the one linked is from Costa Rica and the other one is from Columbia, Brazil and Paraguay.
Must be Adhemarius ypsilon, please, verify. There are several forms (bright and dark) around and this one seems to be very variable. My arguments: The quite large trapezoid shaped patch on the forewing is quite typical and unique for Ypsilon. The whitish spots at the base of the hindwing is also usually seen in Ypsilon (also in others, but then the larger spot is missing). What do you think?
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