Mandibles are reduced and functionless in

Options

A. Cockroach
B. Mosquito
C. Bed Bug
D. Butterfly.

Answer

### Step-by-Step Solution:

1. **Understanding Mandibles**: Mandibles are the jaw-like structures found in many arthropods, primarily used for grasping, cutting, and chewing food. They are an important part of the feeding mechanism in many species.

2. **Examining Different Arthropods**:
- **Cockroach**: In cockroaches, mandibles are well-developed and functional. They are used to cut and grind food.
- **Mosquito**: Adult mosquitoes generally possess mandibles, although some may lack them. However, in most cases, they are functional.
- **Bed Bug**: Bed bugs have mandibles that are functional and used for feeding, as they pierce the skin of their hosts to suck blood.
- **Butterfly**: In butterflies, most species lack mandibles entirely or have them reduced to a very small size, making them functionless. Butterflies primarily feed using a proboscis, which is adapted for sipping nectar.

3. **Identifying the Correct Answer**: Based on the examination of the mandibles in various arthropods, it is clear that butterflies are the ones in which mandibles are reduced and functionless.

4. **Conclusion**: Therefore, the correct answer to the question "Mandibles are reduced and functionless in" is **butterflies**.