Field Guide - Sampling Methods

Worm Classifications | Sampling Methods | Habitats | Human Impacts | Forest Floor Litter

There are four sampling techniques that researchers often use to sample worms: Flip and strip, hand samples, mustard extractions and midden counts.

Preparing Your Site

No matter which sampling method you choose, it is important to prepare your site properly for a worm extraction.

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Flip and Strip

The flip and strip sampling method is the most simple form of sampling and is useful for identifying the number and type of different worm species present in the area.  To do it, all you need to do is flip rocks, flip logs, flip leaves, strip off bark and just generally hunt around for worms.

Best for: Epigeic and endogeic species (though you will also sometimes find anecic species in your sample)

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Hand Sample

Another simple sampling method is hand sampling.  To perform a hand sample, take a small shovel or spade and dig up some soil. It's best to dig down to at least 15 cm; the deeper you dig, the better the sample you'll get. Once you have your pile of soil, use your hand to gently break up the soil and allow it to sift through your fingers until you find all of the worms in the sample.

Best for: All but anecic species, which can sense the vibrations of the digging.

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Mustard Extraction

Performing a mustard extraction is the most effective form of collection to identify the different species and number of earthworms in your sample area.  Mustard is a skin irritant to worms, and soaking an area with mustard water causes the irritated worms to crawl to the surface.  Follow the steps below to perform a mustard extraction.

  1. Mix 2 liters of water with 20 grams of ground yellow mustard seed (mustard powder).
  2. Mark off an area of 25 cm x 25 cm.  This will be your sample area.
  3. Clear the ground of any dry surface litter (make sure not to clear away any earthworms)!
  4. Slowly pour half of the jug of mustard water into the sample area.
  5. Gather any worms that come to the surface into a collection tray. It's important to wait until they are all the way out of the ground before picking them up or you may break them.
  6. After you have gathered all of the initial worms that come to the surface, pour half of the remaining mustard water into the sample area and gather any additional worms that come up.
  7. After you have gathered all of the next round of worms, pour the remaining mustard water over the sample area and wait to see if any more worms surface.

Best for: All earthworm species

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Midden Count

Midden is the scientific name for piles of earthworm poop. Anecic worms (nightcrawlers) form piles of poop around the opening to their burrow holes. These piles are usually quite large (2-5 cm in diameter and 1-2 cm high) and have a burrow hole in the middle. Once you learn to identify middens, you can easily count them. Normally, only one anecic worm lives in each burrow hole, so counting middens will give you a good idea of how many anecic worms are in your sample area.

Best for: Anecic species

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