The transmission of diseases through contamination of food is an economic importance of

Step 1: Analyze the question The question asks which organism is economically important because it spreads disease by contaminating food. The key phrase is "contamination of food."

Step 2: Explain the concept Insects can be harmful or useful to humans:

• Harmful: they spread diseases, destroy crops, and contaminate food.
• Useful: they pollinate crops, produce honey and silk, and serve as food.

Insects that spread disease by contaminating food are usually mechanical vectors. They pick up germs on their legs, bodies, and mouthparts from dirt, sewage, or refuse, then deposit them on food.

Step 3: Evaluate the options

• A. Mosquitoes: They transmit diseases such as malaria, yellow fever, and dengue by biting and injecting parasites or viruses into the blood. They do not do so by contaminating food.
• B. Cockroaches: They live in drains, toilets, and dirty places. They walk over food and utensils, leaving behind bacteria such as Salmonella and E. coli, which cause typhoid, cholera, and dysentery. This matches the question.
• C. Butterflies: They are mainly pollinators. Their caterpillars (larvae) can damage crops, but butterflies do not contaminate food.
• D. Bees: They are beneficial because they pollinate plants and produce honey and wax.

Step 4: Answer The correct answer is B. cockroaches.

Tip: Match the way the disease spreads to the organism:

• Bite → mosquito (malaria)
• Contaminate food → housefly or cockroach (typhoid, cholera)
• Pollinate or make honey → bees and butterflies (useful)