What external changes are visible after the last moult of a cockroach nymph

Options

A. Both fore wings & hind wings develop
B. Labium develops
C. Mandibles become harder
D. Anal cerci develops

Answer

### Step-by-Step Solution:

1. **Understanding Cockroach Development**:
- Cockroaches belong to the phylum Arthropoda and undergo a type of development known as hemimetabolous development, which includes three stages: egg, nymph, and adult.

2. **Identifying the Nymph Stage**:
- The nymph is the immature form of the cockroach. During its development, the nymph undergoes several molts (approximately 13) to grow and eventually transform into an adult.

3. **Recognizing the Last Molt**:
- The last molt of a cockroach nymph is significant because it marks the transition from the nymph stage to the adult stage.

4. **External Changes After the Last Molt**:
- **Wings Development**: One of the most noticeable changes is the development of wings. Nymphs do not have wings, but after the last molt, the adult cockroach will have fully developed forewings and hindwings.
- **Body Size and Shape**: The body of the cockroach will also become larger and more elongated compared to the nymph.
- **Color Change**: The color of the cockroach may change, often becoming darker and shinier as it matures.
- **Reproductive Structures**: In males, the reproductive structures will become visible, indicating sexual maturity.

5. **Conclusion**:
- After the last molt, the cockroach nymph transforms into an adult with fully developed wings, a larger body, potential color changes, and visible reproductive structures.