Which of the following insects has a sucking mouthpart and a gradual life cycle?

True bugs are classified under the order Hemiptera, which is characterized by having piercing-sucking mouthparts. This feature allows them to feed on plant sap or the bodily fluids of other organisms, which is key to their role in the ecosystem as both herbivores and predators of pests.

In addition to their mouthparts, true bugs also exhibit a gradual life cycle, also known as a hemimetabolic or incomplete metamorphosis. This means that they develop through a series of nymph stages, which resemble smaller versions of the adult rather than going through a complete transformation as seen in insects like butterflies. Nymphs gradually develop into adults by molting, without a distinct pupal stage. This life cycle is efficient for many true bugs, enabling them to adapt quickly to environmental changes.

In contrast, butterflies have a complete metamorphosis with distinct larval and pupal stages, flies typically have a similar life cycle with a pupal stage, and grasshoppers, while having a gradual life cycle like true bugs, have chewing mouthparts rather than sucking mouthparts. This distinction makes true bugs the correct answer for the question regarding sucking mouthparts and a gradual life cycle.