Phylogenetic affinities of Phobetinus to other pirate spider genera (Araneae: Mimetidae) as indicated by spinning field morphology

•Spinnerets of Phobetinus (Mimetidae) were studied in detail for the first time.•Two cylindrical spigot synapomorphies confirm placement in subfamily Mimetinae.•Features of piriform/aciniform glands and palps indicate close affinity to Mimetus.•Phobetinus sagittifer genitalia drawings permit easy identification for the first time.•Spinneret-based Phobetinus affinity (high to low): Mimetus, Australomimetus, Ero.

Spinnerets from Phobetinus sagittifer and an undescribed Phobetinus species were examined by scanning electron microscopy to gain a better understanding of this genus' relationships to other genera in the family Mimetidae. Consistent with placement of Phobetinus in Mimetinae, females possessed two synapomorphies of this subfamily; enlarged cylindrical silk gland spigots with domed shafts and a single cylindrical spigot per posterior lateral spinneret (PLS). Spinning field features overall suggest Phobetinus is most closely related to Mimetus, followed by Australomimetus, then Ero. A possible synapomorphy of a clade including Mimetus and Phobetinus is a pair of modified piriform silk gland spigots on each anterior lateral spinneret of adult males located adjacent to the secondary major ampullate silk gland tartipore. These spigots were present in P. sagittifer; however, similarly positioned spigots in the undescribed species were not obviously modified (i.e., wider or with larger openings relative to the other piriform spigots). Close affinity to Mimetus was also indicated by tartipore-accommodated PLS aciniform silk glands in both Phobetinus species. These have been consistently observed in Mimetus, but not in Australomimetus or Ero. Somatic and genitalic drawings of P. sagittifer are provided to aid identification and similarities are noted between male pedipalps of Mimetus and Phobetinus.