The Grey Cracker (Hamadryas februa) is quite a large butterfly.
Its wingspan is 70–86 mm.
The Grey Cracker is often seen basking on tree trunks, adopting a head-downward posture, with the wings flattened against the bark.
Males bask in this position for long periods to await potential mates.
Males can make a cracking sound (the crackling of bacon in a frying pan) when they dart out at passing insects (and people). 
Only males can produce this sound which may possibly deter competing males from occupying the same territory, or could act as a trigger to initiate the response from a female during courtship.
Hamadryas februa is easily confused with Hamadryas feronia, but unlike Hamadryas feronia, Hamadryas februa has red crescents within the ocelli on the hindwings.
There are two subspecies.
This is Hamadryas februa ferentina which is found in Mexico and south to Brazil (and sometimes in southern Texas).

Minca area, Sierra Nevada de Santa Marta, Colombia, 24 October 2014