Tullgren funnel

A Tullgren funnel, also known as Berlese funnel or Berlese trap, is an apparatus used to extract living organisms, particularly arthropods, from samples of soil. The Tullgren funnel works by creating a temperature gradient over the sample such that mobile organisms will move away from the higher temperatures and fall into a collecting vessel, where they perish and are preserved for examination. The illustration shows how it works: a funnel (E) contains the soil or litter (D), and a heat source (F) such as an electric lamp (G) heats the litter. Animals escaping from the desiccation of the litter descend through a filter (C) into a preservative liquid (A) in a receptacle (B). This illustration is merely a schematic, since usually the soil sample will not be crumbled and poured into the funnel (this would inevitably lead to a high amount of soil particles in the preservation fluid requiring laborious work to sort out the soil organisms). In fact, the soil sample is placed on a mesh sieve that will allow the soil animals to pass but should retain most of the soil particles.