What are excretory structures of cockroach ?

Explanation

### Step-by-Step Solution:

1. **Identify the Excretory Structures**: The primary excretory structures in cockroaches are the Malpighian tubules.

2. **Description of Malpighian Tubules**: Malpighian tubules are blind, sack-like structures. This means that one end of each tubule is closed, while the other end opens into the hindgut.

3. **Location of Malpighian Tubules**: These tubules are located between the midgut and hindgut of the cockroach's digestive system.

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