Morphology And Chaetotaxy Of Larvae In Some Panorpidae (Mecoptera) With Phylogenetic Analysis

Larva is the developmental stage of holometabolous insects. The current taxonomy and phylogenetics of insects strongly depend on the adult stage of insects, but the larval characters are considerably overlooked or neglected. Such situation affects the systematic revision and phylogenetic study of insects.Mecoptera is one of the basal lineages in the Holometabolous insects for their larvae have one pair of compound eyes on the head and occupies an pivotal position in the phylogenetic ayalysis of the Insecta. As the most species-rich family in the Mecoptera, Panorpidae comprises 70% of mecopteran species. But larvae have only been obtained in a few species of Panorpidae, and the taxonomy of the larvae of Mecoptera, including Panorpidae is far from complete and comprehensive hitherto.During our recent study of Panorpidae, larvae of twelve species were obtained at the Liping National Forest Park in the Micangshan Mountains; Taibaishan Mountain and the Huoditang Forest Farm in the Qinling Mountains, Shaanxi Province, central China from 2009 to 2010, including Neopanorpa longiprocessa Hua & Chou; Sinopanorpa tincta (Navás); Panorpa magna Chou, P. nanwutaina Chou, P. obtusa Cheng, P. dubia Chou & Wang, P. emarginata Cheng, P. chengi Chou, P. fulvastra Chou, P. sexspinosa Cheng, P. qinlingensis Chou & Ran, and P. bifasciata Chou & WangThe morphology and chaetotaxy of these larvae are described and illustrated in detail by using light and scanning electron microscopy. A cladistic analysis of Panorpidae is presented based on 30 chaetotaxic characters of larvae in 12 species of scorpionflies by a parsimony analysis with the aid of the software PAUP*4.0b10.Characters of larval morphology are various at generic and specific levels: The larvae of Neopanorpa is unique in having depressed line on the head; the larvae of Sinopanorpa are specific in having about 40 ommatidia and 11 sensilla on the maxillary palp; the larvae of Panorpa vary in the head width, number of cup-like depressions on the antennae, density of microtrichia on a sclerite of the epipharynx, shape of prolegs, and number of apterures on spiracles, and so on. Larval morphology is likely to be useful for future taxonomic and phylogenetic analyses of Panorpidae.In Neopanorpa, most setae of the larvae are short and capitate, expanded greatly from the middle part, and dense microtrichia are present along the posterior fringe of A10. In Sinopanorpa, setae are expanded remarkably; the distance between XD2 and SD2 is longer than that between D1 and SD1 on T1; and the disparity of SD2, L1 and L2 are small on T2. In Panorpa, setae are long and slender, expanded only slightly from the distal part; L1 on prothorax and abdomen, L2 on meso- and metathorax, and D1 and SD1 on the trunk are much longer. The setal shape and length show diversity to certain extent in this genus. P. magna is unique for short setae relative to their great body length, the longest annulated setae on abdominal segments and absence of microtrichia posterior to SD2 on A10. In the P. centralis group, setae are remarkably obtuse, broad and longer than those of the P. davidi group.In the cladogram resulted from the phylogenetic analysis, the genus Panorpa is further reconfirmed to be paraphyletic. Both the Panorpa diceras group and the P. centralis group are very likely to be monophyletic and might need to be raised to the (sub-)genus rank. The so-called P. davidi group is more diverse because P. bifasciata is likely the sister taxon to a lineage of Sinopanorpa tincta and the P. centralis group. The genus Neopanorpa might also be a paraphyletic group.The ultrastructure of larval morphology were observed by using electron microscopy and the larval chaetotaxy was applied in the phylogenetic analysis of Panorpidae for the first time. Larval morphology and chaetotaxy could provide valuable data for future systematics and phylogeny of Panorpidae.