some insects get their nutrients by sticking a needlelike mouth part into a plant. which vessel do you believe they are tapping?

The vessel that insects are likely tapping into when sticking a needle-like mouthpart into a plant is called the phloem. The phloem is responsible for transporting sugars, nutrients, and other organic compounds produced by the plant during photosynthesis to different parts of the plant.

To clarify, insects that feed by piercing the plant's tissue and accessing the phloem are referred to as phloem feeders or phloem-sucking insects. These insects have specialized mouthparts, usually in the form of a stylus or stylet, which can penetrate the plant tissues and reach the phloem vessels.

Typically, these mouthparts are specifically adapted to puncture plant cell walls and locate the phloem vessels. Once the insects reach the phloem vessels, they extract nutrient-rich sap, which contains sugars, amino acids, and other essential nutrients vital for their survival and reproduction.

Researchers have identified various insects that belong to this category, including aphids, leafhoppers, psyllids, and whiteflies. Their feeding activity can have considerable impacts on the plants, as they can transmit diseases, cause physical damage, or disrupt the normal plant growth and development.

So, to summarize, insects that feed on a plant's sap by piercing it with a needle-like mouthpart are tapping into the phloem vessels to obtain nutrients.