For collecting earthworms (and I assume you do mean earthworms, rather than any other vermiform taxa), extractions by electricity and chemicals (dilute formalin, spicy mustard solutions) do work. Chemical extraction especially can vary in effectiveness on different species, which could throw off a biomass estimate. The "octet" machines that are designed for earthworm extraction use a high voltage and low amps and send the current in all directions to affect all individuals in that area (see e.g., Weyers et al. 2008). Other methods of delivering current into soil may work but may also be dangerous. Keep in mind that this electricity travels through soil moisture and soil moisture is variable is space and time. My understanding is that the chemicals have a limited lifetime in the soils, but then again you will be altering soil moisture by adding these solutions.
When possible, the best way to get a truly quantitative sample of earthworm populations is to dig a soil monolith (usually 30 x 30 x 10-15 cm) and hand-sort through the soil. That said, extraction methods are widely used and accepted. -Bruce ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Bruce A. Snyder, PhD basny...@ksu.edu Instructor; Coordinator, REU and URM Programs REU: ksu.edu/reu URM: ecogen.ksu.edu/urm.html Earthworms Across Kansas: ksu.edu/earthworm/ Personal: www-personal.k-state.edu/~basnyder/<http://www-personal.k-state.edu/%7Ebasnyder/> Office: 136 Ackert Hall 785-532-2430 Mail: Kansas State University Division of Biology 116 Ackert Hall Manhattan, KS 66506-4901 "How many miles of unexplored caves are there?”
