In the region of the mouth the basal segments were armed with teeth and subserved the purpose of mastication.
Owen's description showed this view to be groundless, and he attributed the extraordinary development of the toucan's beak to the need of compensating, by the additional power of mastication thus given, for the absence of any of the grinding structures that are so characteristic of the intestinal tract of vegetable-eating birds - its digestive organs possessing a general simplicity of formation.
Appendages of 1st pair consisting of three segments, completely chelate, without poison gland; of 2nd pair slender, leg-like, tipped with three claws, the basal segment without sterno-coxal process taking no share in mastication, and widely separated from its fellow of the opposite side; 3rd, 4th, 5th and 6th appendages similar in form to the 2nd and to each other.
They act to increase the efficiency of internal mixer mastication of natural rubber and unsaturated synthetic elastomers where reduction of viscosity is required.
The Sialidae or alder-flies (q.v.) differ from other Neuroptera in the jaws of the larva - which is aquatic, breathing by paired, jointed abdominal gills - resembling those of the imago, and being adapted for the mastication of solid food.