To provide you with the best answer I can, we have to use a few different definitions of "Largest".

The heaviest insect in the world, which probably also has the largest mass of any arthropod is the Goliath Beetle it can grow to around 11.5 cm in length and to a weight of 4.1oz (115 grams). This insect however is found in South Eastern Africa and not South America, I mention it because it probably has to be one of the most fascinating insect in the world.

The heaviest insect in South America is also a beetle, it is called the Acteon Beetle (pictured) the male of this species can grow to 3.5 inches long, 2 inches wide and 1.5 inches thick. It is a kind of rhinoceros beetle ( see horns). It lives in the jungle in the amazon regions of South America.

The longest insect in the world is the Giant Stick Insect which lives in Borneo and can reach a staggering 20 inches long (40 cm).

Hope that answers you question, don't forget to rate my answer : )

  The largest insect found in South America is noctuid. The length of its body is 9cm and width is 27cm when its wings expanded.