Question

In which of the following insects, the adult and grub feed on the grain by making a small hole?

• A. Khapra beetle
• B. Pulse beetle
• C. Rice weevil
• D. Lesser grain borer

Hint:

The rice weevil (Sitophilus oryzae) is characterized by snout-bearing adults and legless grubs, both of which feed internally on grains by boring small holes.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Stored grain pests can be classified as internal or external feeders based on their feeding habits.
Internal feeders complete their larval development inside the grain kernel, and understanding their feeding patterns is essential for pest management.

Step 2: Detailed Explanation:
Let us examine the feeding habits of the listed stored grain pests:
- Khapra beetle (Trogoderma granarium): Only the larvae (grubs) are destructive; they feed externally on grains, while the adults are short-lived and do not feed.
- Pulse beetle (Callosobruchus chinensis): The larvae feed internally inside pulses, but the adults do not feed on stored grains and are primarily involved in reproduction.
- Lesser grain borer (Rhyzopertha dominica): Both larvae and adults feed on grains, but they typically chew grains into fine powder and flour rather than boring clean, small holes.
- Rice weevil (Sitophilus oryzae): This is a classic internal feeder.
The adult weevil uses its strong mandibles at the end of its snout to chew a small hole into a grain kernel to feed.
The female then deposits an egg inside this cavity and seals it with a gelatinous fluid.
The hatched legless grub feeds internally on the endosperm, pupates inside, and the emerging adult chews its way out, leaving a distinct exit hole.
Therefore, both the adult and grub of the rice weevil feed on the grain in this manner.

Step 3: Final Answer
The correct option is (C).