Nuptial feeding and genital coupling of Neopanorpa scorpionflies (Insecta: Mecoptera: Panorpidae) with notal organs of various lengths

Neopanorpa, the second largest genus in Panorpidae, is mainly characterized by the well-developed notal organ on male tergum III. However, it remains largely unknown how the length of the notal organ influences the nuptial feeding behaviour of Neopanorpa. Here, we investigated the nuptial feeding by comparing the morphology of mating-related structures and the genital coupling of a) Neopanorpa lui Chou & Ran, 1981 with a weakly-developed notal organ, b) N. carpenteri Cheng, 1957 with a medium-sized notal organ, and c) N. longiprocessa Hua & Chou, 1997 with an extremely elongated notal organ. The couples of N. lui and N. carpenteri maintain an intermittent mouth-to-mouth mode but do not exchange any edible food. After that the males secrete a salivary mass onto the surface as a nuptial gift, which is distinctly larger in N. carpenteri than in N. lui. Correspondingly, the male salivary glands are more developed in N. carpenteri than in N. lui. Males of N. longiprocessa bear very short salivary glands corresponding to a coercive mating tactic. The genital couplings are similar among the three species of Neopanorpa. The paired hypovalves of males are used to control the cerci of females. The prominent basal processes of male gonostyli grasp the posterior portion of the female medigynium across the intersegmental membrane. The male aedeagus physically couples with the female medigynium to ensure the male phallotreme to connect to the female copulatory pore. The influence of the notal organ length on the nuptial feeding behaviour of Neopanorpa is briefly discussed.