Parsons, "Labial skeleton and musculature of the Hydrocorisae (Heteroptera)," Canadian Journal of Zoology, vol.
Parsons, "Modifications of the food pumps of Hydrocorisae (Heteroptera)," Canadian Journal of Zoology, vol.
The water bugs belonging to the Nepomorpha infraorder include taxa previously placed either in the group of the Hydrocorisae [6-10] or in the group of the Cryptocerata [8, 11, 12].
According to data provided by this author, the labium in typical Nepomorpha (= Hydrocorisae) posseses several characteristic external structural elements for particular families.
The Nepomorpha (Hydrocorisae, Cryptocerata) represent some examples of modified labium in particular taxa that are evidently separated from the Corixidae.
It is contrary to the theory proposed by Parsons , who reported that the intercalary sclerites apparently enabled the holdfast mechanism to operate more efficiently and could have evolved independently several times in the Hydrocorisae in response to functional needs.