Insect

I think that's not Diabrotica, the head shape and sculpture is quite different. It seems to be one of the species of Lema (subfamily Criocerinae) that mimics the colour pattern of Diabrotica (Galerucinae) occurring in the same area. Mimicry between these groups seems to be quite common in the Neotropics. However, I don't know if it's Batesian or Mullerian. If Batesian, I assume that Diabrotica is the model, because they tend to be more common than Lema and many Galerucinae are known to sequester poisonous substances from their host plants for their own protection.

Chrysomelidae, Galerucinae, Luperini, Diabroticina. And most probably a not yet described Diabrotica sp. http://idtools.org/id/beetles/diabrotica/factsheet.php?name=Diabrotica+a1n+sp.+nov.