Materials you may need to conduct earthworm surveys and hints on getting them
Ground yellow mustard powder (not the liquid condiment) used in the liquid extraction method of earthworm sampling can be ordered by bulk from a local food coop. Frontier herbs is a good supplier, you may be able to buy direct from them, I've never checked. Use the non-organic, I found the organic to not work as well because they use a different plant species which doesn't seem to pack the same wallop.
1-lb of powdered yellow mustard does about 11 samples
After trying many different preservation jars and vials, I prefer to use polypropylene centrifuge tubes for preservation of earthworm samples. They are mostly unbreakable (unless you drive your car over them) and have good fume and leak proof lids. I order mine online from Midwest Scientific and though there are several different types, I like the "TPP Centrifuge Tubes" with yellow tops in both 15ml and 50ml sizes. The 50ml size is nice for sample plots with a lot of worms and the 15ml size is nice for sample plots with fewer worms. I typically put all the worms from one sample plot in one vial (sometimes you need 2 if there are LOTS of large earthworms).
BE SURE TO LABLE YOUR VIALS FULLY AND COMPLETELY WITH PERMANENT MARKER AS YOU COLLECT THEM! There is nothing more frustrating than trying to figure out which vials go with which samples hours, days, months or years after you collected them.
Any kind of alcohol works to anesthetize your earthworms before final preservation. I use rubbing alcohol (70% isopropyl) because it is the cheapest and easiest to obtain. Believe it or not, it is usually cheaper to buy it at your local drug store than to order it through a lab supply house.
Formalin is used in the final preservation step of your earthworm specimens. It is a biological fixative which prevents decay and keeps the specimen relatively firm and in good condition for years to come. After the earthworms have been fixed in formalin for at least 48 hours, they can be transferred back into alcohol for long-term storage and the formalin can be re-used. I typically order mine from Fisher Scientific and use “Fisher PROTOCOL, 10% Buffered Formalin (traditional fixative, buffered to a neutral pH)” (~$51 for 4L).
BE AWARE – formalin is a known carcinogen and needs to be handled and stored using appropriate safety equipment (latex gloves, apron, eye protection) in a well ventilated area.
Additional Field Supplies
Forceps (4-5 inch) with blunt tips are handy to have when collecting earthworms using the liquid extraction method.
Plastic or aluminum collection trays
Used to collect your earthworms and anesthetize them in the alcohol as they come up. Once collection is completed, you can transfer them to the vial. They can stay in alcohol for the day, but get them in formalin within 24 hours or they get mushy.
Sturdy gallon jugs with a nice screw cap are great for mixing and carrying your mustard juice for the liquid extraction method (old windshield wiper fluid jugs, large fruit juice jugs with handles, etc.). Standard plastic milk jugs work fine too, but don’t last as long. HINT – wash them out after you use them, after few days they can really stink up the place if they haven’t been cleaned out.
If you are using a sample plot to sample earthworms it is handy to have a frame made of wood or aluminum that you can lay down to define your sample plot. I don’t count on it to hold in the liquid in when using the mustard extraction method, but more to define the sample area. I recommend the frame be 33cm x 33cm for consistency and easy in data calculations (see Conducting Your Own Studies) and about 2-3 inches high.
Print data sheets off our website or create your own. Depending on the conditions, you may want to use “write in the rain” paper. HINT – write with pencil on data sheets, it doesn’t run (like pen does) when the data sheet gets wet. You don’t want to loose all that data you collected when you get caught in the rain at the end of a long day!
Other handy items include a clipboard, gallon sized ziplocks to collect your sample vials in, extra pencils and markers, and maybe rain gear. Also remember yourself! Bring water to keep yourself well hydrated while working and a treat to reward your yourself for a job well done at the end.