Comparative Immature Morphology And Biology Of Panorpa Liui And Panorpodes Kuandianensis(Mecoptera)

Holometabolous insect as most successful lineage of terrestrial animal have completelydivergent morphological and biological features between adult and immature stages. Theimmature stages occupy a considerable part of the life cycle of insects in Endopterygota (=Holometabola). However, previous morphological studies are mainly focused on adults.Mecoptera, one of the most primitive lineages of Endopterygota, is unique for bearing apair of compound eyes in the larval stage. The systematic position of Mecoptera iscontroversial. The systematic relationships of the mecopterous families, especially Panorpidaeand Panorpodidae, are also ambiguous. The previous systematic analyses are mainly based onmolecular or adult morphological characters. Detailed larval morphological studies inMecoptera, especially in Panorpodidae are quite scarce.During our biological observation and artificial rearing, the immature stages of Panorpaliui Hua,1997(Panorpidae) and Panorpodes kuandianensis Zhong et al.,2011(Panorpodidae)are successfully obtained for the first time. The biological characters of P. liui and Pd.kuandianensis were described for the first time. The comparative morphological study onPanorpidae and Panorpodidae was made under light and electron microscopy for the firsttime.The immature stages of Panorpidae and Panorpodidae share amount similarities onexternal morphology: The eggs are both oval, with irregular network on eggshell. The larvaeare both hypognathous, with mandibulate mouthparts, three-jointed antennae, inflated pediceland slender flagellum, three pairs of four-segmented thoracic legs, nine pairs of spiracles (theprothoracic ones on lateroposterior corner of the prothoracic shield, the abdominal ones onpleura of abdominal segments1–8) and a protrusile sucker on telson (providing assistantattachment during locomotion). Otherwise, the larval head capsule bears13pairs of setae inboth families.The larvae of Panorpidae and Panorpodidae are somewhat different. Firstly, the pairedcompound eyes (each consists of26ommatidia) are present on the lateral surfaces of thelarval head in Panorpidae but absent in Panorpodidae. Secondly, the abdomen bears eightpairs of prolegs in Panorpidae but seven unpaired proleg-like processes in Panorpodidae. Thirdly, two ventral setae (V1and V2) are on abdominal segments1–7in Panorpidae, butonly one (V1) in Panorpodidae. Fourthly, the setae are either setiform or clavate in Panorpidaebut all setiform in Panorpodidae. Fifthly, the annulated setae on abdominal segments arepresent in Panorpidae but absent in Panorpodidae. Furthermore, the morphology of thecuticular spinules on larval trunk and the sensilla on larval head of the two families are alsodifferent.The biological characters of Panorpidae and Panorpodidae are also diverse. Thescorpionflies of P. liui complete two generations per year with color polymorphism but onlyone generation in Pd. kuandianensis. The adults feed on dead arthropods and occasionally onpollen in P. liui, but only feed on pollen and nectar in Pd. kuandianensis. Both malescorpionflies in the two families offer nuptial gifts during copulations. However, the male P.liui only offers a prey as nuptial gifts and Pd. kuandianensis only offers salivary masses.The sister relationship of Panorpidae and Panorpodidae is confirmed on the basis of ourcomparative study on larval morphology and previous larval morphological studies inNannochoristidae, Boreidae and Bittacidae. Otherwise, the mecopterous larvae possessseveral common features by which the group as a whole can be distinguished from the otherAntliophora (Diptera and Siphonaptera). Mecoptera is confirmed to be a monophyly.