Which order, known as Tetrigrade or pygmy grasshoppers, features a pronotum highly elongated to cover the abdomen and a tarsal formula of 2-2-3?

• A. Acrididae
• B. Gryllacrididae
• C. Tetrigrade
• D. Plecoptera

Answer: (C)

The feature being tested is the distinctive body plan that defines pygmy grasshoppers (Tetrigidae), often called Tetrigrade. These insects have a highly elongated pronotum that covers the abdomen like a shield, giving them a compact, wedge-shaped appearance. They also show a specific tarsal formula: two segments on the front and middle legs (2 on each of those pairs) and three segments on the hind legs (2-2-3). That combination of an abdomen-covering pronotum and the 2-2-3 tarsal arrangement is characteristic of this group. The other groups don’t share these defining traits: their pronotal shape and leg segmentation differ from this shield-like abdomen-covering form, so they don’t match the described features.