Feminine.

Helopeltis larvalis Horn, 1873: 137; by monotypy.

Medium sized beetles, body length 4–7 mm. Body shape oval in dorsal view, dorsoventrally flattened, with dorsal outline nearly straight along medial third in lateral view (Fig. 33); surface even and granulate. From yellowish, orange brown to dark brown in coloration, usually with patterns along elytra, with different areas of head and pronotum darkened. Shape of head somewhat trapezoid (Fig. 11L). Anterior corners of frons extended laterally and posteriorly, emarginating anterior margin of eyes. Eyes of moderate size, somewhat oval, anteriorly deeply emarginated, not projected from outline of head. Clypeus somewhat pentagonal, laterally explanate, with anterior margin usually straight (Fig. 11L). Labrum concealed by clypeus (Fig. 11L). Mentum with surface variably sculptured, usually with oblique and transverse striae (Fig. 33C). Antennae with eight antennomeres, with cupule strongly asymmetric and oval in outline. Maxillary palps slender, slightly longer than greatest width of head; inner margin of maxillary palpomere 2 weakly and evenly curved, and outer margin weakly curved along apical third (Fig. 33C). Pronotum with surface of lateral areas flat. Elytra without sutural striae, with outer margins laterally explanate; serial punctures clearly aligned in longitudinal rows (Fig. 33A). Scutellar shield U-shaped. Surface of prosternum flat, to medially bulging, smooth to irregularly sculptured. Posterior elevation of mesoventrite only weakly bulging, with pair of lateral, longitudinal, low ridges; anapleural sutures nearly parallel along anterior section, separated anteriorly by distance slightly shorter than anterior margin of mesepisternum. Metaventrite uniformly covered by hydrofuge pubescence, with medial, narrow, and slightly carinate glabrous patch; posterolateral glabrous patches reduced. Protibiae with spines of anterior row short and semi erect; apical spurs of protibiae reduced, much shorter than protarsomere 1. Metafemora with tibial grooves moderately developed; hydrofuge pubescence covering 5/6 of anterior surface (Fig. 33C). Tarsomeres 1–4 ventrally densely covered by setae; metatarsomere 2 longer than 3 and 4 combined, 1 nearly as long as 3, and 5 nearly as long as 2–4 combined. Fifth abdominal ventrite apically emarginate, with fringe of flat and stout setae. Aedeagus divided (Fig. 34), parameres separated from each other for most of their lengths; median lobe divided in dorsal and ventral plates; dorsal plate usually strongly sclerotized; ventral plate bilaterally bifurcated, forming thick lateral lobes along apical region; basal piece nearly 0.2 × the length of parameres, always noticeable; gonopore not clearly visible.

Helobata is one of the most conspicuous genera of acidocerines, especially in the New World. The flattened and broadly explanate body shape and concealed labrum, accompanied by granulose surface, long and slender maxillary palps and well-defined elytral serial punctures, are quite unique in the subfamily. The only genus that shares some of these features is Helopeltarium, except that the latter has short maxillary palps, smooth surface and lacks serial punctures along the elytra. The configuration of the aedeagus (Fig. 34), in particular the thickness of the lateral lobes of the ventral plate of the median lobe, is also unique among acidocerines.

Nearctic: United States (California, Florida, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Virginia). Neotropical: Argentina, Bolivia, Brazil (Amazonas, Ceará, Mato Grosso, Mato Grosso do Sul, Pará, Rio de Janeiro, Roraima), Cuba, Guatemala, Mexico, Paraguay, Suriname, Venezuela; Fig. 5.

Species of Helobata occur primarily in open habitats with abundant vegetation. According to Clarkson et al. (2016), specimens of Helobata are uncommonly encountered and occur in marshes, swamps, and ponds, most often in small numbers, although they are rarely found in modest amounts (dozens of individuals; Short, pers. obs.). According to Archangelsky (1997), they can be found in slow moving creeks or rivers, living among the littoral vegetation or on floating plants. They are attracted to lights. Females have been observed carrying their egg cases attached to the ventral side of their abdominal ventrites (Archangelsky 1997).

The larva (first instar) and egg case are only known for Helobata larvalis; these immature stages were described by Spangler and Cross (1972). A differential diagnosis of the first instar larva was provided by Fikáček (2003).

This genus was described by Horn (1873) under the name Helopeltis, which was preoccupied by Helopeltis Signoret, 1858 (Hemiptera). Bergroth (1888) proposed the name Helobata as a replacement name for Helopeltis Horn, whereas Cockerell (1906a) proposed the name Helopeltina. Helobata has priority, so it is the currently valid name for the genus, which was revised by Fernández and Bachmann (1987).

There are 13 species of Helobata described to date. The type species, Helobata larvalis (Horn), has generally been known under the name Helobata striata (originally published as Hydrophilus striatus Brullé, 1841: 58, which is a primary homonym of Hydrophilus striatus Say, 1825 [now Berosus striatus (Say)]; therefore unavailable. The name Helobata larvalis (Horn) was then reinstated by Hansen (1991: 293). Photos of a syntype of Helopeltis larvalis (Horn) are available at https://mczbase.mcz.harvard.edu/guid/MCZ:Ent:101 (accessed 9 January 2021). The external morphology of members of Helobata is very homogeneous. Some variation can be observed in the shape of the clypeus (e.g., Fernández 1987; Clarkson et al. 2016). Helobata is the only Neotropical genus truly widespread in the New World, as it ranges from southeastern North America, all the way to Argentina and Southern Brazil.

Helobata cuivaum García (paratype), H. larvalis (Horn), and H. lilianae García (paratype).

Horn 1873: original description of the genus and the type species; Spangler and Cross 1972: description of egg case and first instar larva; Fernández and Bachmann 1987: review of the genus, description of four new species from Argentina, Brazil and Paraguay; García 2000: three new species from Venezuela; Makhan 2007: two new species from Suriname; Clarkson et al. 2016: two new species from Brazil, review and new country records of Brazilian species; Clarkson and Almeida 2018: new records from Brazil; Short et al. 2021: phylogenetic placement.