I recognize it as a species of "wheel-bug" or, as others have noted, a species of assassin-bug. (I don't know the specific species, though; sorry.)
These predators have a vicious "bite" using hypodermic mouth-parts, and some routinely inject a type of enzyme in the "venom/saliva" that causes great burning or pain; the compound is intended to help the creature suck the internal organs out of "prey" creatures. Depending on the species' size, these may even kill and consume young frogs and toads.
As noted by others, the younger ones stick soil, plant-matter and other material to their exoskeleton as camouflage. This is because, in part, they are cannibalistic; parents and elders have no compunctions about eating their smaller offspring. Of course; if the youngsters get a chance, they will dine on their parents or elders, too.
Aside from some wasps that lay eggs on the paralyzed bodies of spiders, these insects are one of a very limited number of species that will often actively hunt down and prey on spiders.