Which insects are phytophagous in nature?

The correct answer is Option (4) - Insects which feed on plant sap and other parts of plants.

Phytophagous insects are those that feed on living plant material, such as leaves, stems, flowers, fruits, or plant sap. These insects obtain their nutrition directly from various parts of living plants. Common examples include aphids, caterpillars, and beetles that consume leaves, stems, or extract plant sap.

• Insects that live on animals are usually parasitic, such as lice or fleas, and are not phytophagous.
• Insects that feed on dead plant tissues are known as detritivores, not phytophagous, as they consume decaying organic matter.
• Insects that live on epiphytes may or may not feed on plants, but epiphytes themselves are plants that grow on other plants.

Phytophagous insects specifically feed on living plant parts, making them plant eaters