Biología

Different functional groups of soil arthropodofauna present in the agro-ecosystem can be severely modified by tillage practices. The abundance of different trophic groups subject to conventional tillage (CT) and no tillage (NT) practices were evaluated compared to a natural field boundary (FB) in a wheat crop. Arthropods were captured using pitfall traps and collected every 20 days during 10 months, and grouped according to their habits in predators, phytophagous and detritivorous. Tillage systems affected the abundance of arthropod fauna and the proportion between different functional groups as regards a FB. Predators constituted the most abundant group of all arthropods captured, and their number was higher under NT than under CT. In CT, an increase in predators was observed only in spring, probably associated with a recolonisation from the adjacent plots of NT. Phytophagous was the least representative group in the three evaluated systems, it was higher under cropped plots (NT and CT) than in the FB, and was not affected by tillage practices.Under NT, the number of predators, remained higher along the crop development. Phytophagous activity in no till plots remains constant. In FB, the number of captured individuals was lower and relatively stable along the whole sampling period than in the cultivated plots.Ploughing action (CT plots) provoked a decrease in the relative importance of predators and an increase in phytophagous as regards those in NT and FB. Total biomass of captured arthropod fauna showed significant differences between treatments, being higher in NT and lower in CT plots.It is concluded that tillage systems affect not only the abundance of arthropod fauna but also the proportion between different functional groups. The consequences of these changes for soil quality are discussed later on.

The prevalence of the parasitic disease Pediculosis capitis was studied over a period of one year from 1-8-1992 to 31-7-1993, in Sanitary Region XI of the Buenos Aires province, Argentina which is composed of 15 districts located on the ENE, and in other areas under the influence of the Hospital Interzonal de Agudos, Especialidad Pediatría "Sup. Sor María Ludovica" de Plata, center of this Sanitary Region. A total number of 552 individuals of from medium to medium low social level of the child population of from 0 to 16 years of age were sampled at random over 52 consecutive weeks. All individuals who actually had the parasite at the time of examination were considered as positive for this disease. The results are expressed in terms of prevalence and its monthly and seasonal variations analyzed. Prevalence showed high values during all months, the lowest being in February (12%) and the highest in August (56.8%), the annual mean being of 38.04% (+/- 4.05%). Seasonally, its lowest value occurred in the summer (16.8%), the values for the remaining seasons being very similar to one another, but always higher than 38%.

The new species Aquanirmus major Cicchino & González Acuña found on the Great Grebe, Podiceps major, from different localities of Argentina and Chile, is described and illustrated, giving comments on its affinities and differences with the remaining three species included in the Aquanirmus emersoni-species complex.

A new species of the genus Brueelia Kéler is described as parasitic on the Common Diuca-Finch, Diuca diuca diuca, based on specimens from three localities in Chile: Punitaqui (Coquimbo Province), La Rinconada (Colchagua Province) and Chillán (Ñuble Province). The species is fully described and illustrated, and brief comments on its morphological affinities with allied species are also made.

Two new species of the genus Brueelia Kéler, 1936 are described of two species in the genus Phrygilus Cabanis, 1844 from Punitaqui, Coquimbo, IV Región, Chile: Phrygilus gayi (Gervais, 1834) and P. fruticeti (Kittlitz, 1833). Descriptions were made in a comparative form, adding comments on their relatives, as well as an account of all Brueelia species known to infest South American Emberizine finches.