A Review Work on How to Differentiate the Longhorn Grasshoppers Ruspolia differens and Ruspolia nitidula (Orthoptera: Tettigoniidae)

The record of potential characters differentiating the longhorn grasshoppers Ruspolia differens Serville, 1838 and Ruspolia nitidula Scopoli, 1786 in the family Tettigoniidae of the order Orthoptera is somewhat unapparent, being randomly featured in the general literature of the individual species without joint synchronization. The present work systematically re-examines and re-organises these characters with a main goal to harmonizing the various records where the two species are interchanged, misdiagnosed or incorrectly named, and sensitizing future workers to overcome the oversights. The couple of insects are evidently sister species that are well distinguished from each other by their respective species-specific biology and biogeography. R. differens inhabits the Sub-Saharan African region; the species has a swarming phase and colour polymorphism with six morphs, and a distinct sex dimorphism with males having longer antennae and a unique pair of metathoracic flaps. On the other hand, R. nitidula is exclusively solitary, greenish and Palearctic ranging in Asia, Europe and Northern Africa. Generally, each species is morphologically, behaviourally, genetically and thus taxonomically distinct from its counterpart.