Half-jumping plant lice – a taxonomic revision of the distinctive psyllid genus Togepsylla Kuwayama with a reassessment of morphology (Hemiptera, Psylloidea)

Togepsyllinae is a distinctive group within Psylloidea, with its systematic status treated variously by different authors. Of the only two known genera, Togepsylla is better known and distributed in temperate and tropical East Asia. In this study, the taxonomy and morphology of Togepsylla was studied in detail. Keys to adults and fifth instar immatures of the genus are provided. Togepsylla glutinosaesp. n. is described, and T. matsumurana, T. takahashii, and T. tibetana are redescribed. Syncoptozus is compared with Togepsylla for differences in morphology. Modern psyllids have evolved their jumping hind legs via the elongation of the dorsal edge of coxa, the broadening of coxal wall, the thickening of meron, the backward twisting of the plane of trochanter, femur, and tibia, and the enlargement of trochanteral tendon. However, in Togepsylla, this modification has progressed halfway. The metapleuron of Togepsylla is arranged in a different way than other psyllids. The pleural sulcus is short, and the metepisternum and trochantin are not divided. Wax-secreting fields on abdominal sternites, resembling those of whiteflies, are found on all Togepsylla species, and described for the first time. Other distinctive characters of the genus are also revealed, e.g. frons completely fused with gena, a pair of extra sclerites present behind the base of thoracic furca, one-segmented aedeagus, and absence of a flag lobe on valvula dorsalis of ovipositor. Based on various similarities in morphology, Togepsyllinae may have a close relationship with Aphalaridae-Rhinocolinae and is possibly related to Homotomidae, Liviidae-Liviinae and Atmetocranium (Calophyidae). All the distinctive characters of Togepsyllinae suggest that the current placement of the group is doubtful, and the phylogeny of Aphalaridae needs to be resolved.