Functional morphology of the mouthparts in the scorpionfly Sinopanorpa tincta (Mecoptera: Panorpidae)

The feeding mechanism of insects can be deduced from the morphology of their mouthparts. The mouthpart morphology of the scorpionfly Sinopanorpa tincta (Navás) was investigated using light and scanning electron microscopy. The mandibulate mouthparts of S. tincta are situated at the distal end of the rostrum, which is formed from the elongation of clypeus and subgenae. The blade-shaped mandible terminates in two inwardly curved sharp teeth. The paired maxillae each consist of a triangular cardo, an elongated stipes, a hirsute galea, a spiny lacinia, and a five-segmented palpus. Rows-arranged claw-like spines are first found to occur on the mesal side of the lacinia. The labium is composed of a basal elongated membranous submentum, a central vase-shaped mentum, and a short distal prementum, which distally carries a pair of two-segmented labial palpi. The proximal labial palpomere is very hirsute on mesal side and well sclerotized at the basal part of the lateral side. On the baso-mesal side of the distal labial palpomere is a triangular area, which is densely furnished with long microtrichia. Various sensilla are concentrated on the epipharynx, maxillary and labial palpi. The pattern of thick basiconic sensilla at the apex of epipharynx exhibits distinct sexual dimorphism. The feeding mechanism is conjectured from the ultramorphology of the mouthparts. We suggest that scorpionflies are likely to feed on liquid food of their prey after extra-oral digestion. Hair brushes on the hirsute epipharynx, galeae, laciniae, labial palpi, and hypopharynx might serve to filtrate large particles.