Neoplea Paraplea Plea Pleidae, the pygmy backswimmers, is a family of aquatic insects in the order Hemiptera (infraorder Nepomorpha, or "true water bugs").

[1] Pleidae belong to the Tripartita which contains the more advanced lineages of true water bugs, and are closely related to the true backswimmers (Notonectidae), but closer still to the Helotrephidae, another family of tiny Nepomorpha, which usually swim upside-down and, like the Pleidae, have a sensory organ in the center of the clypeus.

[9] By and large the Pleidae may be considered an effectively flightless group when it comes to biogeography and dispersal into new habitat.

The sounds they produce apparently have an intraspecific communication function, as the animals are able to perceive and react to them.

[12] Possibly they make sounds to maintain contact among the loose swarms in which the Pleidae roam their habitat[citation needed].

Unlike true backswimmers (Notonectidae), they are completely harmless to humans, as their rostrum is far too small to pierce skin.

[9] Their hindleg claws enable them to clamber through vegetation which apart from swimming is their main form of locomotion.

Thus, the belly has higher buoyancy, resulting in the animal turning upside down as soon as it lets loose from the substrate.