In Rieger's  system the clade Ochteridae + Gelastocoridae (Ochteroidea) was shown in the second branch, while the Corixidae were presented as the third branch.
The monophyly of the lineage Ochteridae + Gelastocoridae (Ochteroidea) is supported by 3 unambiguous synapomorphies (2-3), (34-2), and (35-1).
The sister group relationship between the Ochteroidea and the Aphelocheiridae is found in 73% of the trees, and a relatively high bootstrap value of77% also supports this relationship for the Potamocoridae.
 was generally congruent with the traditional classification of Mahner ; however, a new superfamily of the Aphelocheiroidea (Aphelocheiridae + Potamocoridae) was evaluated, and moreover the Naucoroidea were restricted to only one family (Naucoridae) and the Ochteroidea received a new position (Ochteridae + Gelastocoridae).
, on the basis of four Hox genes, supported the monophylies of the Nepomorpha, Naucoroidea (Aphelocheiridae + Naucoridae), Nepoidea (Belostomatidae + Nepidae), Ochteroidea (Ochteridae + Gelastocoridae), and Pleoidea (Pleidae + Helotrephidae); the Ochteroidea were the most basal lineage; the Notonectoidea contained Notonectidae only and formed a new sister relationship with the (Pleoidea + Naucoroidea) and the sister relationship with (Nepoidea + Corixoidea).
Then, the superfamily Ochteroidea (Ochteridae and Gelastocoridae) is positioned bellow the Corixoidea, however, in a different position from the one it had in the cladogram developed by Hebsgaard et al.
Mahner's (1993) scheme differs from Rieger's (1976) in the position of Corixidae, which is considered the sister group of (Ochteroidea
+ (Naucoroidea + Notonectoidea)); whereas in Rieger's scheme the position of the Ochteroidea
and Corixidae are inverted [i.e., (Ochteroidea
+ (Corixidae + ("Naucoroidea" + Notonectoidea)))].
From a cytogenetic point of view Nepomorpha may be regarded as containing five groups: Nepoidea, Ochteroidea, Naucoroidea, Corixoidea, and Notonectoidea.
Taking into account the phylogenetic relationships of families and superfamilies of Nepomorpha proposed by Rieger (1976) and Mahner (1993), the <<primitive>> superfamilies Nepoidea and Ochteroidea show both simple and multiple sex chromosome systems (XY and [X.sub.n] Y), and lack m chromosomes.
On the other hand, the m chromosomes had become lost at the origin of the superfamilies Nepoidea and Ochteroidea. Summarizing, both the X0 and [X.sub.n]0 systems in Corixoidea, Naucoroidea and Nepoidea, and the absence of a pair of m chromosomes in Nepoidea and Ochteroidea should be considered as derived characters within Nepomorpha.
There is evidence pointing to a close relationship between the Gelastocoridae and Ochteridae which, taken together, have formed the Ochteroidea
, but the Aphelocheiridae are rather distal in relationship from those families and have formed the Aphelocheiroidea together with the Potamocoridae .
(2) In this study, it has been estimated that the closed stylet groove on the first and second segments indicates one synapomorphy for the Ochteridae and Gelastocoridae and establishes a sister group relationship between them, supporting their presence at the superfamily level (Ochteroidea