Which of the following structures is not a part of excretory system of cockroach?

Options

A. Malpighian tubules
B. Fat body
C. Nephrocytes
D. Nephridia

Answer

To determine which structure is not a part of the excretory system of a cockroach, we need to understand the components of the excretory system in cockroaches and compare them with the options provided.

### Step-by-Step Solution:

1. **Understand the Excretory System of Cockroach**:
- The excretory system of cockroaches primarily consists of structures like Malpighian tubules, fat bodies, and nephrocytes.
- These structures are responsible for the removal of nitrogenous waste from the body.

2. **Identify the Structures**:
- **Malpighian Tubules**: These are the main excretory organs in cockroaches. They help in the removal of waste products from the hemolymph (blood) and are involved in osmoregulation.
- **Fat Bodies**: These are involved in the storage of nutrients and play a role in metabolism, but they also assist in excretion by processing waste.
- **Nephrocytes**: These are specialized cells that help in the excretion of waste materials.

3. **Evaluate the Options**:
- If the options include structures like Malpighian tubules, fat bodies, nephrocytes, and nephridia, we need to identify which one does not belong to the cockroach's excretory system.
- **Nephridia**: This structure is characteristic of the phylum Annelida (e.g., earthworms) and is not found in cockroaches.

4. **Conclusion**:
- The structure that is not a part of the excretory system of a cockroach is **nephridia**.

### Final Answer:
**Nephridia** is not a part of the excretory system of cockroach.

---