Which of the following pests is known to have sucking mouthparts?

Leafhoppers are indeed known for possessing sucking mouthparts, which they use to extract sap from plants. This feeding behavior not only harms the plant by depriving it of essential nutrients but can also lead to the transmission of plant pathogens, such as viruses. Their mouthparts are specifically adapted for piercing plant tissue, allowing them to efficiently access the sap contained within.

In contrast, billbugs, grasshoppers, and flea beetles utilize different feeding mechanisms. Billbugs have chewing mouthparts, grasshoppers primarily feed on vegetation using their robust mandibles to bite and chew plant material, and flea beetles also possess chewing mouthparts, allowing them to consume parts of leaves. Therefore, leafhoppers are the only pests among the options listed that utilize sucking mouthparts, highlighting their unique feeding strategy in comparison to the others.