Abstract The feeding habits of Chironomidae in hill streams in the pampean region have not been described. In this study, we analyzed the gut contents of this insect family with an aim at establishing their diet in an intermittent stream in the Ventania-Hill system. We sampled three sites with different habitat characteristics (i. e., altitude, substrate type, and current velocity). Of the total of nine taxa were recorded, the only one present at all sites was Corynoneura sp. 1. The food items found were detritus, diatoms, filamentous chlorophytes, euglenophytes, vascular plants, fungi, and animal remains. Most of the taxa could be classified as gathering collectors, with those having a higher proportion of detritus in the gut contents although the guts of Pentaneura nr. cinerea, Cricotopus sp. 1, and Onconeura analiae included high proportions of animal remains. No differences in the feeding habits were attributable to the location in the stream. This research contributes to our understanding of the trophic habits of Chironomidae in an intermittent hill stream system of South America.

Resumen Se llevó a cabo un estudio bianual en un área protegida del Sistema serrano de Ventania donde la estepa pampeana y las cabeceras de los arroyos mantienen las condiciones cercanas a las naturales. Se analizó la composición y la estructura del ensamble de Chironomidae (Insecta: Diptera) en dos arroyos prístinos y su relación con las variables fisicoquímicas. Se identificaron 15444 especímenes, correspondientes a 37 especies distribuidas en 4 subfamilias. El ensamble presentó una estructura más similar a las reportadas para los arroyos de la región Andina o extra Andina, que la de otras áreas de la región pampeana. Orthocladiinae presentó la mayor riqueza taxonómica y densidad, mientras que Podonominae las menores. Chironominae estuvo mejor representada aguas abajo, presentando géneros con distribución amplia. De los 5 géneros de Podonominae reportados en la región Andina-Patagónica, 3 de ellos (Podonomus Philippi, ParochlusEnderlein y Podonomopsis Brundin) fueron colectados. La presencia de Podonomus y Podonomopsis representa el registro de menor altitud para ambos géneros. Las variables fisicoquímicas difirieron entre las estaciones, y la conductividad fue la única que mostró un gradiente altitudinal. Las especies que prevalecieron en los sitios pedemontanos, correlacionaron positivamente con la conductividad. Con pocas excepciones, las especies recolectadas se registraron en otoño y primavera. En el arroyo Toro, la densidad fue significativamente mayor en la primavera del segundo año. Nuestro estudio aporta información de base sobre la ecología y la sistemática de un grupo de insectos ampliamente utilizado en estudios de biomonitoreo de ambientes acuáticos, lo cual resulta muy importante para respaldar la importancia de preservar esta área.

Abstract A two-year study was conducted in a conservation area of the Ventania hill system where the Pampean grassy steppes and their headwater springs maintain conditions close to natural ones. The composition and the structure of Chironomidae (Insecta: Diptera) along two short hill pristine streams and their relationship with the physicochemical variables were analyzed. A total of 15444 individuals belonging to 37 species of four subfamilies were identified. An assemblage structure more similar to those described for Andean or Argentine extra-Andean hill streams than to those of the surrounding Pampas was observed. Orthocladiinae showed the highest and Podonominae the lowest taxonomic richness and density. Chironominae was best represented downstream by genera with wide distribution. From the five Podonominae genera reported in the Andean-Patagonic region, three of them (Podonomus Philippi, Parochlus Enderlein and PodonomopsisBrundin) were collected. The presence of Podonomus and Podonomopsis represent the reports at lower altitudes for both genera. The physicochemical variables differed between seasons, and only water conductivity showed an altitudinal gradient. Those species prevailing in piedmont sites correlated positively with conductivity. With few exceptions, the species collected were recorded in both seasons. In Toro stream, density was significantly highest in Spring of the second year. This study provides the ecological and systematic baseline knowledge of an insect group widely used in biomonitoring of aquatic environments, to provide biological information that supports the importance of preserving this area.

Abstract Studies of the relationships between the temporal variation of biological phenomena and environmental factors are essential to understanding the dynamics of communities. Phenology is a structuring element and, together with voltinism, is related to timing of reproductive activities. The aim of this study is to ascertain the structure and composition of the Chironomid assemblage and its emergence patterns in relation to the environmental variables through the use of the Chironomid pupal exuviae technique using the Neotropical streams as a model. The streams presented similar species compositions. The highest density of pupal exuviae was recorded during spring and the greatest richness in late summer and early autumn. Chironominae presented greater prevalence throughout the year with oscillations for Orthocladiinae and Tanypodinae. Chironominae and Tanypodinae presented emergence peaks in spring-summer and Orthocladiinae in autumn-winter. Rainfall, photoperiod and water and air temperatures structured the Chironomid assemblage, influencing emergence. Univoltine, bivoltine and multivoltine species were recorded. The species presented interspecific synchronization in emergence peaks at different times of the year.

ABSTRACT A new monotypic genus and species of predaceous midge from the southernmost area of the Argentinean Yungas, Yungahelea australis Spinelli and Ronderos, is described and illustrated from male and female adults. It belongs to a group containing the Ceratopogonini genera Parabezzia Malloch, Diaphanobezzia Ingram and Macfie, Spinellihelea Borkent, Grogan and Picado, Leptohelea Wirth and Blanton, and Fittkauhelea Wirth and Blanton. Phylogenetic interpretation indicates that Yungahelea is the sister group of Spinellihelea or the clade composed by Parabezzia and Diaphanobezzia.

The study of the type material of Chironomus (Polypedilum) griseistriatum Edwards, 1931 described from Patagonia lead us to formally transfer the species to Apedilum Townes, 1945 as a new combination, and a reared specimen allows us to describe its pupa. Based on several larvae belonging to Apedilum collected in the proximity of the localities in which the adults and pupae were found, we tentatively describe the larval stage. Subfossil larval head capsules of the same species were found in Laguna Stibnite at 46°S in Chile dated to about 2,500 years ago and in Puerto Blest, Lago Nahuel Huapi at 41°S in Argentina dated about 2,000 years ago. We discuss the habitat of the species based on both modern and subfossil material. Identification keys to male adult, pupae and fourth instar larvae are also provided.

El estudio del material tipo de Chironomus (Polypedilum) griseistriatum Edwards, 1931 de Patagonia nos permite transferir formalmente la especie a Apedilum Townes, 1945 como una nueva combinación, y la cría de un especimen nos permite describir su pupa. Sobre la base de varias larvas pertenecientes a Apedilum colectadas en las proximidades de las localidades en las cuales fueron encontrados los adultos y las pupas, describimos tentativamente el estadio larval. Cápsulas de larvas subfósiles de la misma especie fueron encontradas en la Laguna Stibnite a 46°S en Chile datadas en aproximadamente 2.500 años atrás y en Puerto Blest, Lago Nahuel Huapi a 41°S en Argentina datadas en aproximadamente 2.000 años atrás. Discutimos el hábitat de la especie basados en el material moderno y subfósil. Se provee además de claves de identificación del cuarto estadio larval, pupa y adulto macho.

The first report of Parochlus Enderlein from Ventania hill system is presented, being the first record of the genus from Buenos Aires province. The description and illustration of the female adult of Parochlus carolinae Rodriguez et al. is presented and the original male and larval descriptions are emended. Characters from the pupal thoracic horn are emphasized to distinguish P. carolinae from other Parochlus species.

Se presenta el primer reporte de Parochlus Enderlein del sistema serrano de Ventania, el cual constituye el primer registro de este género de la provincia de Buenos Aires. Se describe e ilustra la hembra de Parochlus carolinae Rodriguez et al. y se enmiendan las descripciones originales del macho y de la larva. Se remarcan caracteres del cuerno torácico de la pupa para distinguir P. carolinae de otras especies del género Parochlus.

Adults male and female of Labrundinia separata (Edwards), and the immatures are described and illustrated. The studied specimens were collected as immatures in the Notophagus forest of northern Argentinean Patagonia, and reared to adult in laboratory. The species is compared with the most similar cogeners.

Se redescriben e ilustran los adultos macho y hembra, y se describen los inmaduros de Labrundinia separata (Edwards). Los ejemplares estudiados fueron colectados como inmaduros en los bosques de Notophagus del norte de la Patagonia Argentina y criados, hasta adultos, en laboratorio. Esta especie es comparada con sus congéneres más similares.

The male and female of the new species Metriocnemus puna sp. n from the Argentinean Puna are described and illustrated. A parsimony analysis including 24 well-described species of the genus plus the new species based on the adult male was conducted in order to access the phylogenetic position of the new species and to provide the first phylogenetic hypothesis for the genus.

This is the first report of the non-biting midge Metriocnemus eryngiotelmatus Donato & Paggi 2005 associated to the impounded water of Dipsacus fullonum L. plants.

Esta es la primera cita de Metriocnemus eryngiotelmatus Donato & Paggi 2005, asociado al agua almacenada en las axilas de Dipsacus fullonum L.