The head of the earwig Forficula auricularia (Dermaptera) and its evolutionary implications

摘要

The external and internal head morphology including the musculature of the common earwig Forfcula auricularia is described in detail.We specifed and corrected previous descriptions and provided a detailed documentation. The head of Forfcula is characterized by prognathism, generalized mandibles with a mesal cutting edge distally of the mola and its drop-shaped appearance. We added the followingnew apomorphies for Dermaptera to the various previously reported ones: (I) coronal and frontal cleavage lines with corresponding stronginternal strengthening ridges; (II) the division of the praementum into a basal and a distal sclerite; (III) the presence of a bumpulus at the tip of the paraglossa; (IV) the presence of large distal palpilla on the terminal maxillary and labial palpomeres and (V) the origin of M. tentoriohypopharyngealis on the submentum. Another potential apomorphy are the lateral lobes on the distal hypopharynx which are mostlikely not homologous to the superlingua of apterygote insect. Other characters such as the prominent ball-and-socket joint between scapusand pedicellus or the unique antennal heart are poorly studied within Dermaptera and therefore cannot be phylogenetically polarized. Incontrast to the various ordinarial apomorphies, the dermapteran head exhibits only one potential synapomorphy with other polyneopteranorders: the absence of the linguactual tendon and the associated muscle that is shared with Plecoptera and/or Zoraptera. Our results showthat additional studies of the presumingly basal splits of Dermaptera are required to understand the head evolution of the group.