Which of the following belongs to the order Isoptera?

The correct answer is termites, as they are the only insects listed that belong to the order Isoptera. This order is specifically characterized by social insects that live in colonies and are primarily known for their wood-eating habits. Termites play a significant ecological role by breaking down cellulose, which aids in nutrient cycling in the environment.

Understanding the characteristics of termites reveals they are closely related to cockroaches, sharing similarities in their life cycles and social behaviors. The term "Isoptera" translates to "equal wings," which refers to the structural similarity of the wings in some species of termites.

In contrast, the other insects mentioned—grasshoppers, silverfish, and bed bugs—belong to different orders entirely. Grasshoppers are known for their jumping ability and belong to the order Orthoptera. Silverfish are part of the order Thysanura, recognized for their distinctive appearance and behaviors. Bed bugs, notorious for their biting habits, fall under the order Hemiptera. Each of these insects has unique behaviors and ecological roles, highlighting the diversity of insects within various orders in the class Insecta.