The Copulatory Behaviors And Their Morphological Basis In Panorpidae (Mecoptera) With A Description Of A New Genus

Courtship and copulatory behaviors are essential to reproduction in amphigonous insects.The elaborate genitalia and other related structures play an important role in courtship andcopulatory behaviors of insects. These structures, genital or non-genital, comparing with othertraits, show the same pattern of relatively rapid divergent evolution. However, in previousstudies, these structures have been widely used in taxonomy research as morphologicalcharacteristics. Limited researches were focused on copulatory mechanism and functionalmorphology of related structures.Panorpidae (common name: scorpionflies) is the largest family in Mecoptera. Thecourtship and copulatory behaviors in Panorpidae are characterized by diverse nuptial feedingbehavior and well studied by ethologists. Scorpionflies are regarded as model insects fortesting aspects of mating systems. Their sexual behaviors have been studied in some detail.However, research of morphological basis and mechanism of sexual behavior in Panorpidaehas been neglected.Based on observation of intersexual behaviors in Panorpidae, in combination with lightand electron microscopy, we studied the courtship and copulatory behaviors of Panorpidae, aswell as copulatory mechanism, morphological basis of copulation, including genital andnon-genital contact structures in aspects of function, morphology and ethology. We havecompared the morphological and behavioral characters of Panorpidae at both specific andgeneric level. The main results are as follows:The scorpionfly Neopanorpa longiprocessa Hua and Chou,1997were investigated forits sexual behaviors and functional morphology of the notal organ and genitalia. It is the firstbehavioral study of genus Neopanorpa. In N. longiprocessa, the mating behaviors occurwithout nuptial feeding. The morphological basis of this non-nuptial copulation may berelated with the developed notal organ in the male. The notal organ serves a function to coerce the female during copulation. Only males that succeed in seizing the female by notal organwill establish genital contact and copulate. In the male genitalia, the epandrium (tergum IX)has developed a pair of ventral bulbs to grasp the subgenital plate of the female; thehypandrium has a pair of dorsal processes to control the abdominal end of the female. Wepresume that these adaptations of N. longiprocessa might represent another evolutionarypathway different from Panorpa to overcome female resistance. These results show that notall scorpionfly copulatory behaviors are characterized by nuptial feeding. Presumably, thedeveloped grasping apparatuses are compensating traits in scorpionflies that provide nonuptial gifts, as exemplified by N. longiprocessa.Based on the observation of the courtship and copulation behaviors in Dicerapanorpamagna (Chou in Chou et al.,1981), we investigated morphological basis and mechanism ofintersexual behaviors. Different from known Panorpa species, during the courtship, no ediblenuptial gifts being provided to attract the female. The visual display (“dancing”) and sexpheromone used to “calling” the female. After a phase of non-nuptial feeding copulation, themale secretes salivary mass as nuptial gift. The specialized paired anal horns are used asnon-genital contact structure to seize the abdominal segment VIII of the female. Somespecialized structures in the male genitalia (including gonostylus, epandrium, and hypandrium)are used to grasp particular part of the female during copulation. The flexible hypandriumcould be used to stimulate the abdominal end of the female. We inferred that these pecializedstructures may be used to maintain the genitalic contact and enhance male ability to controlover copulation during copulation.The mating behaviors of scorpionflies are very diverse at genetic and species levels. The nuptialfeeding behavior is even not universal in Panorpidae. There is considerable interspecific andintergeneric variation in male mating tactics. The nuptial feeding copulation could be replacedby coercion and that the morphological modification of the male has been evolved to adaptthe sexual conflict from the females in scorpionflies.Based on comparative morphology study, we inferred that the non-genital contactstructures, which contact females directly during copulation, also show a pattern of diversityalong with elaborate forms that is typical of more strictly genital structures.Genus Dicerapanorpa was erected with Panorpa magna Chou1981as its type species.The genus is recognizable by the following characters: body yellowish with two blackishlateral longitudinal stripes on dorsum; tergum VI of males with two anal horns; abdominalsegment VII of males much thinner at the basal half and abruptly thicker at apical half;parameres of males trifurcate; female genital plate with the axis not extending beyond themain plate. Six new combinations, Dicerapanorpa magna (Chou in Chou et al.,1981), D. diceras (MacLachlan,1894), D. stotzneri (Esben-Petersen,1934), D. tjederi (Carpenter,1938),D. kimminsi (Carpenter,1948) and D. triclada (Qian and Zhou,2001) are transferred fromgenus Panorpa Linnaeus. Dicerapanorpa baiyunshana Zhong and Hua,2013andDicerapanorpa shennongensis Zhong and Hua,2013are described and illustrated. A key tothe genera of Panorpidae is updated.In this paper, we discussed the relationship between copulatory behaviors and theirmorphological basis, and the evolution of diverse mating behaviors in Panorpidae.