SIFTING AND BERLESE PROTOCOLS

R.S. Anderson

Canadian Museum of Nature, P.O. Box 3443, Station "D", Ottawa, Ontario, Canada K1P 6P4

Many small arthropods live in various kinds of decaying organic material. Collection of this material and the separation of the arthropods from it reveals an assemblage of cryptic taxa not generally collected in other ways. For many taxa, species diversity in this assemblage is generally high and species distributions are often restricted, likely because dispersal powers are often limited by loss of wings and/or eyes. Various forests have been sampled for litter arthropods by sifting general forest floor leaf litter followed by extraction using berlese funnels which employ light bulbs (standard 60W) as their source of heat. General forest floor leaf litter usually yields many species, but attempts should also be made to specialize on other focal substrates such as flower and fruit falls, vertebrate nest materials, concentrations of fungi or twigs, or similar concentrations of any kind of organic material. Specialized habitats in all areas should yield valuable and perhaps unique collections. Grasslands have not been sampled extensively for substrate micro-arthropods and methods may require modification as field experience develops. Materials under larger woody shrubs should be given special attention, as should litter under grass clumps, vertebrate nest materials, and litter in riparian situations (including stream washup). Selection of various types of substrate debris will diversify the sampling results but sampling effort and diversity of substrates sampled should be consistent across sites to permit meaningful comparisons.

Field sampling should first consist of selection of site and or focal substrates. The selected material should then be sifted using a standard entomological sifter with about 1cm hardware cloth as a screen. Litter, to the level of the soil only, should be scraped into the sifter. Approximately 6 litres of sifted litter should be collected as one sample. This sifted litter is placed in a cotton pillowcase (or similar receptacle), labelled and tied. Four such samples are taken for each selected sampling period in that habitat or microhabitat. Samples can be kept in the pillowcases in the laboratory for up to 4-5 days as long as they are turned frequently and not exposed to excess moisture or extreme temperatures.

Processing in the laboratory consists of placement of 2 litres of litter in each Berlese funnel and heating, using light bulbs, for 6 hours. Extracted insects should fall into 80% ethanol. The specimens extracted from three funnels should represent a sample. General litter samples should be taken at monthly intervals; special substrates should be sampled when encountered. As in all sampling protocols, feedback should ensure the maximally efficient deployment of resources.

In grassland habitats the amounts of litter stated above may prove excessively time consuming to collect for special substrates. Amounts should be adjusted accordingly as experience dictates. Taxa sampled will include small beetles, ants, small flightless Hymenoptera and Diptera, spiders, mites, millipedes, centipedes and numerous larval stages of various taxa.

Equipment needed for sampling:

Sifters (2-4), Berlese funnels (12 [moveable]), supports for funnels, gloves, trowels, pillowcases, light bulbs, cheesecloth, jars, alcohol, whirlpac bags. The construction of sifters and Berlese funnels is described in Martin (1977).

Reference

Martin, J.E.H. 1977. Collecting, preparing, and preserving insects, mites, and spiders. The insects and arachnids of Canada Part 1. Research Branch Canada Department of Agriculture, Publication 1643. 182 pp.