Head anatomy of adult Sisyra terminalis (Insecta: Neuroptera: Sisyridae) – Functional adaptations and phylogenetic implications

• A salivary pump consisting of a reservoir and two muscles is described.
• The salivary pump is an adaptation to feeding on aphids.
• Paraglossae and ligula form a secondary prolongation of the salivary system.
• This prolongation is an adaptation to feeding on desiccated honeydew.
• Three new synapomorphies for Neuropterida and one for Neuroptera are recognized.

The external and internal head anatomy of Sisyra terminalis is described in detail and compared with data from literature. A salivary pump consisting of a peculiar reservoir and a hitherto unknown muscle, M. ductus salivarii, is newly described for Neuroptera. The upward folded paraglossae form a secondary prolongation of the salivary system. These structures are discussed as functional adaptations for feeding on aphids and desiccated honeydew. In a phylogenetic analysis the basal position of the Sisyridae within Neuroptera is retrieved. The following new synapomorphies are postulated: (1) for Neuropterida, the presence of a M. submentomentalis and prepharyngeal ventral transverse muscles, and the absence of a M. submentopraementalis; (2) for Neuroptera and Sialidae, the presence of a mandibular gland; (3) for Neuroptera, the presence of four scapopedicellar muscles; (4) for Neuroptera exclusive Nevrorthidae and Sisyridae, the weakening of dorsal tentorial arms, the presence of a M. tentoriomandibularis medialis superior and the shifted origin of M. tentoriocardinalis.