Pneumorids resemble Acridoids in many respects and are clearly related to these, but the exact nature of the relationship is uncertain. There have been no morphology-based cladistic tests of these hypotheses. A molecular phylogeny is under construction. However several genera and species are known from only one sex or a single individual and are of dubious status. Genera with non-inflated males are particularly troublesome.
Present data suggest that neither view is correct.
A non-inflated male morph occurs alongside the inflated male in at least two species. However, the situation of Parabullacris vansoni with respect to the B. unicolor complex is less clear. Kluwer Academic Publishers, Dordrecht. The bladder grasshopper. On the stridulating organs of Cystocaelia immaculata .