SIMULIIDAE (DIPTERA) FROM QUEQUÉN GRANDE RIVER AT LAS CASCADAS (BUENOS AIRES, ARGENTINA): POPULATION VARIATION AND RELATIONSHIP W ITH TEM PERATURE, STREAM DISCHARGE AND PRECIPITATIONS

Abstract

Quequén Grande is a river plain of the Southern area of Buenos Aires province; the river source is in the
Tandilia mountain system and has a permanent flow. The area has a températe climate and rains are more or
less uniformly distributed all over the year. Black fly larvae and pupae were sampled mostly biweekly during
26 monlhs at Las Cascadas area, about 15 km North Necochea city. Two species, Simulium (Psaroniocompsá)
bonaerense Coscaron & Wygodzinsky and S. (Thyrsopelma) orbitale Lutz, were found. The former was
more abundant and was present all along the year. Immatures density of S. bonaerense do not show correlation with temperature, precipitation or stream discharge. S. orbitale shows negative correlation with temperature.