José Ricardo Inacio Ribeiro

The small species of Belostoma Latreille (Heteroptera, Belostomatidae). III

Species of the oxyurum group (sensu Lauck) consist of five extant Neotropical small species, whose lengths range 15.0 to 20.0 mm. The anterior interocular width about 1.5 times the width of an eye and ventral diverticulum of phallus flattened, circular, and large are, in combination, diagnostic. The small species of the oxyurum group were included in the Lauck´s key to the identification of the species groups, without dealing with the species included in it because many of them are very similar in appearance. Therefore here we redescribe and key the Belostoma species of the oxyurum group. Belostoma oxyurum (Dufour) is newly recorded from Brazil (Parana and Rio Grande do Sul). Holotype and lectotype are designated for B. oxyurum and B. sanctulum Montandon, respectively. The aspect of the prosternal keel, the ratio between the width of the ventral diverticulum of phallus and its length in ventral view, and the aspect of dorsal arms of ventral diverticulum have proven useful for better species delimitation. Based on specimens from Para State (N. Brazil), Belostoma carajaensis Ribeiro & Estevez, sp. nov. is described and illustrated. This new species differs from B. sanctulum in having anteoculus shorter than interoculus and the dorsal arms of ventral diverticulum divergent and large. A male specimen of B. noualhieri Montandon was collected in Sao Paulo State and based mainly on features of male genitalia, this species is here also included under oxyurum group.

A synopsis of the Hydrometra (Hemiptera, Heteroptera, Hydrometridae) from the Amazon River floodplain, Brazil, with redescription of Hydrometra argentina Berg

Hydrometra argentina Berg, 1879, H. caraiba Guerin-Meneville, 1857 and H. guianana Hungerford & Evans, 1934 are newly recorded in the Amazon River floodplain, Brazil. A redescription of H. argentina is also given, as the original description is incomplete. A key to the three known species occurring in this region is provided. Hydrometra argentina can be distinguished from H. caraiba and H. guianana by the body length smaller than 12.50 mm, anteoculus/postoculus ratio between 1.80 and 2.00, clypeus narrow and conical, metacetabulum with no circular pits, and projections on male abdominal sternite VI in the shape of simple spines. The other species can be distinguished mainly by the anteoculus/postoculus ratio and position of projections on male abdominal sternite VI.

Duas novas espécies de Belostoma Latreille, 1807 (Hemiptera: Heteroptera: Belostomatidae) do grupo plebejum sensu Nieser, 1975

Species of plebejum group comprises seven extant small species of giant water bugs. This group is currently reported from Honduras to southern South America. Two new species are described as a result from a revisional study of this group: Belostoma estevezae Ribeiro & Alecrim, sp. nov., from Mato Grosso State, Brazil, and B. nessimiani Ribeiro & Alecrim, sp. nov., from Amazonas State, Brazil. The prosternal keel of B. estevezae, sp. nov., is similar to that of B. nicaeum Estevez & Polhemus, 2007, while the male genitalia structures of B. nessimiani, sp. nov., is similar to those of B. parvum Estevez & Polhemus, 2007. A key to the species of plebejum group with new species included is also provided.

Redescription and Taxonomic Considerations of Belostoma gestroi Montandon, 1900 (Heteroptera: Belostomatidae)

Belostoma gestroi Montandon, 1900, is redescribed and its distribution is mapped. This species is newly recorded from the Brazilian states of Amazonas and Mato Grosso do Sul, and the Argentinan province of Formosa. Specimens from Argentina and Paraguay are designated lectotype and paralectotype, respectively. Notes on intraspecific variations are given. The previously unknown prosternal keel and phallic variations are described and figured for the first time. The vertex with a longitudinal median carina is a condition not found in the other species of the B. dilatatum group. However, this carina is often weakly in B. gestroi.

On the biology of Buenoa platycnemis (Fieber) (Insecta, Heteroptera, Notonectidae) at Restinga de Maricá, Rio de Janeiro State, Brazil

A monthly quantitative study on B. platycnemis (Fieber, 1851) was carried out in a sand dune marsh, on the littoral of Rio Janeiro State. The aims of this study were to correlate the life cycle of the species with the seasonal regime of the water body, defining steps of the annual cycle, age strueture, and to indicate oviposition sites and trophic relations. The species shows a marked seasonal tendency. The major steps of the life cycle obtained were an invernal (weak) with a predominance of imagines, followed by another of population expansion, characterized by the absence of adults, massive eclosions and predominance of low instar nymphs. Probably, B. platycnemis has a sensibility to water levei variation and might be intluenced by the concentration of Spirogyra sp. (Chlorophyceae) in the water column. In relation to oviposition, B. platycnemis has not shown preference for any macrophyte, since eggs were found in Rhynchosphora corymbosa (Linnaeus) Britton (Cyperaceae), Eleocharis sellowiana Kunth. (Cyperaceae) and Nymphoides indica (Linnaeus) O. Kuntze. (Menyanthaceae). The observed predators of B. platycnemis were Anax amazilli (Burmeister, 1839) (Aeshinidae), Eryihemis credula (Hagen, 1861) (Libellulidae) and other Odonata, nymphs and adults of Belostoma candidulum Montandon, 1903 (Belostomatidae), Notonecta (Paranecta) disturbata Hungerford, 1926, Buenoa antigone antigone (Ki-rkaldy, 1899) (Notonectidae), besides Curicta cf. tibialis (Martin, 1898) and Ranatra horvalhi Montandon, 1910 (Nepidae). Larvae of Sayomyia sp. (Chaoboridae), Chiro-nomus spp. and Labrundinia sp. (Chironomidae), Callibaetis gutlatus Navas, 1915 (Baetidae), cladocerans and copepods are potential prey of B. platycnemis, while ostracodes were refused.