Your very handsome bug caught my attention. I agree with Daniel that it is in the family Coreidae, and very possibly in the genus Thasus. You could also check out the very closely related (sometimes synonymous) genus Pachylis. There are numerous photos of juvenile T. acutangulus and P. hector on the internet, all of which look very similar to your bug, but it is unclear to me that either species occurs as far south as Ecuador. One reference I found did suggest Brazil for P. hector, but most indicate that they are Central American species. Perhaps it is another species in one of those genera. The link below is for Spanish paper that may be helpful, assuming your Spanish is better than mine. Good luck. Karl.

http://www.ejournal.unam.mx/zoo/066-01/ZOO66106.pdf