Gerromorpha Popov, 1971

Ghahari, Hassan, Moulet, Pierre, Ostovan, Hadi & Linnavuori, Rauno E., 2013, An annotated catalog of the Iranian Dipsocoromorpha, Enicocephalomorpha, Gerromorpha, Leptopodomorpha and Nepomorpha (Hemiptera: Heteroptera), Zootaxa 3641 (4), pp. 301-342 : 305-306

Infraorder Gerromorpha Popov, 1971

Gerromorpha is sister group to the Panheteroptera, (i.e., Nepomorpha, Leptopodomorpha, Cimicomorpha, and Pentatomomorpha) (Schuh & Slater 1995), and because members of Nepomorpha are found back into the late Triassic, the Gerromorpha must be of at least the same age (Damgaard 2008). Usually the gerromorphans (or semiaquatic bugs) are small to medium-sized (1.5 to more than 20 mm), rarely large insects. The body is covered by very minute setae which protect insects against UV rays (Cheng et al. 1978). Antennae are 4-segmented and longer than the head, inserted in front of the eyes and completely visible from above. The dorsal head surface has three pairs of trichobothria (long slender setae inserted in deep cuticular pits) near the inner margin of the compound eyes. Usually the rostrum is thin and 4-segmented. The prothorax is differentiated into a large lobe which covers the scutellum and the base of the hemelytra (except, in Hebridae and Mesoveliidae ). The hind legs are the longest, the fore legs the shortest. In Veliidae and Gerridae fore legs are raptorial. The tarsi possess underneath numerous water-repellent setae (the comb) which allow walking on water. Fore wings, when present, lack claval commissure and are not divided into corium, clavus, and membrane. Alary polymorphism is very common (particularly in Gerridae ) and according to Andersen (1973) is in relation with sexual activity, but we also know several other reasons for it (e.g., migration). Male genitalia are symmetric; and female ones are plate-like, except in Mesoveliidae they are saber-like. All species are predators and consume small arthropods in their biotope but themselves are prey of ripicolous and aquatic arthropods (spiders, ants, beetles, backswimmers), frogs, toads, and birds. Eggs with thin choria are laid in wet biotopes or in the water. Gerromorphans inhabit the surface of both freshwater and saline waters (Schuh & Slater 1995; Andersen & Weir 2004; Chen et al. 2005).

Dufour (1833) separated Gerromorpha (as Amphibicorises) because of their ability to walk on the water; Fieber (1851) changed this name in Gymnocerata. Reuter (1910) created two sections: Hydrobiotica and Anonychia (which respectively represent Nepomorpha + Ochteridae + Gelastocoridae + a large part of Gerromorpha and, on the other hand, Geocorisae + a part of Gerromorpha + Enicocephalomorpha). Stichel (1955) classified them as Amphibicoriomorpha. Popov (1971) after serious morphological and biological studies divided the Heteroptera into 5 suborders of which Leptopodomorpha included the actual Gerromorpha and Leptopodomorpha. Štys & Kerzhner (1975) from their part divided Leptopodomorpha sensu Popov in Gerromorpha and Leptopodomorpha, which is the present classification. The most comprehensive work on Gerromorpha is by Andersen (1982), who summarized our knowledge on these insects. Damgaard (2008a, c) with the help of the DNA studies gives another approach of the phylogeny of Gerrromorpha.

Gerromorpha are distributed worldwide and it is possible to find them from the equator to subpolar tundra. Gerromorpha contain 4 superfamilies and 8 families worldwide, including more than 125 genera and about 1600 species. All superfamilies and five families are represented in the Palearctic Region and Iran.