Definition: Insect mouthparts that are concealed inside the head by folds of the head capsule. The mandibles and maxillae are located inside the oral chamber, and only the tips of the mouthparts protrude from the oral opening.
Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
