Silvia A. Mazzucconi

Distributional patterns of Chacoan water bugs (Heteroptera: Belostomatidae, Corixidae, Micronectidae, and Gerridae)

Distributional patterns of South American species of aquatic and semiaquatic Heteroptera from the Chaco biogeographic province were analyzed. Based on a track analysis of 60 species of Belostomatidae, Corixidae, Micronectidae, and Gerridae, five generalized tracks were found:(1) Bolivia, and northwestern and central Argentina (Belostoma dallasi, Ectemnostega montana, E. quechua, E. stridulata, E. venturii, Sigara tucma, S. yala, Tenagobia pulchra, Eurygerris fuscinervis, and Trepobates taylori); (2) southern Brazil, eastern Bolivia, Paraguay, and northeastern Argentina (Belostoma bosqi, Heterocorixa brasiliensis, Tenagobia selecta tarahui, and T. schadei); (3) southeastern Brazil and northeastern Argentina, determined by Belostoma candidulum, B. testaceopallidum, Heterocorixa nigra, Sigara hungerfordi, Brachymetra furva,Halobatopsis spiniventris, Metrobates plaumanni plaumanni, and M. vigilis; (4) southeastern Brazil, Uruguay, and central western Argentina (Belostoma cummingsi, B. martini, Sigara argentiniensis, Tenagobia fuscata, and T. carapachay); and (5) southern (Trichocorixa milicorum, Sigara santiagiensis, and S. forciceps). Three panbiogeographic nodes have been determined:(1) northeastern Argentina, in the intersection of generalized tracks 2 and 3; (2) central Argentina, in the intersection of generalized tracks 1 and 4; and (3) central Argentina, in the intersection of generalized tracks 4 and 5. In spite of these complex patterns, these results show that the Chaco province appears to be a natural biogeographic area.

Morphometry and chaetotaxy of the nymphs of Ectemnostega (Ectemnostegella) quechua (Bachmann 1961) (Insecta: Hemiptera: Heteroptera: Corixidae)

The egg and the five nymphal instars of Ectemnostega quechua are described and illustrated for the first time. The eggs of Ectemnostega have a short stalk, and the shape, size and chorionic structure differ among groups of species. The nymphal characters most useful in identifying instars I–V of Ectemnostega are: body length; number of rostrum sulcations; number of setae on inner surface of protibiotarsus; spines and setae, and spines on posteroventral surface of mesofemur and mesotibia, respectively; setae on posterodorsal surface of mesotibia and mesotarsus; spines and setae on anteroventral surface and setae on posterior surface of metatibia; swimming hairs on anteroventral and posterodorsal surfaces of metatarsus; and the grade of development of wing pads. The nymphs of E. quechua can be easily distinguished from other species of Ectemnostega by the number of spines and setae on the posteroventral surface of mesofemur.

Paravelia anta sp. n. and P. hungerfordi (Drake and Harris) from South America (Heteroptera: Veliidae)

Paravelia anta sp.n. from Argentina and Paraguay is described and compared with its close relative P. hungerfordi (Drake & Harris) from Brasil, which is redescribed. In addition, characteristics to separate these two from the remaining species of Paravelia are given.

A new species of Martarega White, 1879 from South America (Hemiptera: Heteroptera: Notonectidae), with an identification key to all described species of the genus

Martarega guarani sp. n. is described and illustrated from north-eastern Argentina (Misiones Province), based on brachypterous forms of both sexes and macropterous females. Comparisons with its close relative M. uruguayensis are included. The hind femur with a basal notch extending some distance beyond the apex of the trochanter and conspicuous enlargement contiguous to this notch distinguish the female of M. guarani sp. n. from those of all the remaining species of Martarega. The following combination of characters distinguish the male of M. guarani sp. n. from those of all the remaining species of Martarega: total body length less than 6.5 mm; metaxyphus trilobed with median lobe bluntly rounded; hemelytra of brachypterous form opaque with a narrow straight hyaline stripe running medially almost entire length of wing and a second short one at base of the hemelytral process; anterior surface of middle trochanter with a group of cohesive lanceolate setae on a nodule; anterior surface of middle femur without a nodule. An identification key to the brachypterous form of all described species of Martarega is given. The distribution, habitat preferences and association between species of M. guarani sp. n. are presented.

Studies on the chorionic structure of the eggs of Corixoidea (Hemiptera: Heteroptera) with scanning electron microscopy

The chorionic structure of the eggs of sixteen species of Corixoidea (Ectemnostega (Ectemnostega) quadrata (Signoret), E. (Ectemnostegella) quechua (Bachmann), Trichocorixa mendozana Jaczewski, Centrocorisa kollari (Fieber), Heterocorixa brasiliensis Hungerford, Sigara (Aphelosigara) tucma Bachmann, S. (Tropocorixa) denseconscripta (Breddin), S. (T.) platensis Bachmann, S. (T.) rubyae (Hungerford), S. (T.) santiagiensis (Hungerford), S. (T.) schadei (Hungerford), S. (T.) yala Bachmann, Tenagobia (Incertagobia) incerta Lundblad, T. (Fuscagobia) fuscata (Stål), T. (Schadeogobia) schadei Lundblad, and T. (Tenagobia) pulchra Hungerford) is described for the first time using scanning electron microscopy. In addition, the eggs of some of these species are described based on color and morphometry. The sculpturing of the chorion and the structure of the micropylar area here in studied using scanning electron microscopy together with the length of the stalk distinguish the eggs of the genera (except Sigara, genus without a uniform pattern on the sculpturing of the chorion) and subgenera (including Aphelosigara and Tropocorixa) of Corixoidea present in Argentina. The above mentioned characters, together with the egg length, proved to be useful for the identification of the Argentinian species. An identification key to the eggs of Argentinian species of Corixoidea based on the material herein studied, and additional data present in the literature, is provided.

Notes on Paravelia paxilla (Drake), with Description of the Male Form (Heteroptera: Veliidae)

The male of Paravelia paxilla (Drake) is described and the female redescribed. New records and ecological notes are included. Paravelia paxilla is compared with its close relatives P. splendoris (Drake & Harris) and P. willei (Drake & Harris).