What characteristic defines chewing insects?

Chewing insects are characterized by their sharp, powerful mandibles, which are adapted for biting and grinding plant material. This adaptation allows these insects to effectively consume larger pieces of plant tissues, such as leaves, stems, and roots. The strength and structure of their mandibles enable them to tear the plant cells apart, facilitating a more direct method of feeding compared to other types of feeding structures.

In contrast, long proboscises are typically found in sucking insects, which feed on fluids rather than solid plant tissues. While many chewing insects can exhibit flight capabilities, the ability to fly is not a defining characteristic of chewing; some may be flightless. Insects that feed on fluids are distinct from chewing insects as they utilize their specialized mouthparts specifically designed for siphoning liquid nutrients rather than mechanically breaking down plant material. Therefore, having sharp, powerful mandibles specifically denotes the chewing behavior of these insects.