Comparative And Functional Morphology Of The Mouthparts In The Mecoptera

Mecoptera is one of the basal lineages in the endopterygote insects. The research on comparative morphology of mouthparts in Mecoptera has important significance to reveal the evolution and phylogeny of Mecoptera. Exemplified with the Sinopanorpa tincta (Navás), the feeding mechanism of the Panorpidae (Mecoptera) was studied by using light and scanning electron microscopy. And the mouthpart ultra-morphology was compared among 12 species of Panorpidae, two species of Bittacidae and one species of Panorpodidae for the first time. The main results are as follows:The mandibulate mouthparts of Panorpidae 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 carries distally 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. 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.Twelve species of scorpionfly in Panorpa Linnaeus, Neopanorpa Weele, and Sinopanorpa Cai & Hua were morphologically studied for their mouthpart ultramorphology. They are different in the pattern of basiconic sensilla on the apex of epipharynx, the length of prementum and hairs on hypopharynx and two teeth of mandibles. The mouthpart morphology in Sinopanorpa and Neopanorpa can be easily distinguished. The pattern of thick basiconic sensilla at the apex of epipharynx exhibits distinct sexual dimorphism in Sionpanorpa tincta. In Panorpa, however, the mouthpart morphology differs among the ten species examined. The diversity of the mouthpart morphology in Panorpa further confirms it is a paraphyletic genus, which might need to be further split.Based on comparative studies of the rostrum, mandibles, prementum and microstructures of membrane, a possible relationship can be drawn among these three families. Panorpodidae might be one of the relatively basal lineages in Mecoptera. On the contrary, Bittacidae should represent the most advanced family. Feeding behavior in Panorpodidae and Bittacidae is also discussed briefly.