build a berlese

 

what is that litter critter?

 

litterlinx

 

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Using a homemade Berlese funnel to sample the litter

 

The goal of litter sampling is to extract the invertebrates, many quite small, that live in the dead leaves, twigs, and needles that lie on the ground. When a good patch of litter is sampled, it is amazing how many things you discover that are living, unseen, right below our feet.

 

To start the sampling you need some version of a piece of equipment called, variously, a tullgren or berlese funnel. For a classroom of 30 students, it is quite possible to run 10 or 15 berleses at once.  All you need is this equipment:  a liter pop bottle (preferably clear plastic, the labels are often lightly glued on), a bit of hardware cloth (with a mesh of ca ¼ inch), a desk lamp or similar light source (bulbs are, ideally, 20-40W, not much higher), and a small dish with alcohol to catch the litter critters.

Building Your Berlese Funnel

About 5 and ½ inches up the side of the pop bottle, start a small hole then use scissors to cut the bottle in two.  Place the small dish of alcohol (70% rubbing alcohol is fine) at the bottom of the bottle. When you invert the top half, it should nest snugly in the base. The gently tapered top of the bottle becomes our funnel!

 

 

Now cut out a piece of hardware cloth about 3 inches square. Be careful here, because the points of stiff wire can scratch. Fold up the corners as shown to build a roughly square platform that will nest inside the funnel part of the bottle.

 

Where do you look for litter?

Litter is everywhere, even on this relatively manicured college campus. When you study the brown food web, you see habitats everywhere.  How many litter habitats can you see in this picture?  I see at least three.

1--Under evergreen bushes there is usually a lovely litter layer 1 cm deep. The litter underneath evergreens (e.g., junipers, pines, spruce) may yield very distinctive species.

 

2—The finest litter is often embedded in a smooth lawn. To gather it, make your hand look like a little rake, and run it through the lawn. Again, grass litter may yield different species in different numbers.

 

 3—In ornamental plantings, there is often times lots of litter, in this case, leaves from nearbye pin oak trees have blown in and lodged there.

All you need to harvest litter is something in which to carry the litter back to your berlese funnel. Here I use a plastic bowl and crawl under the bush—a habitat that few people experience!

 

Good litter is slightly moist (but not wet). It has been sitting around a while, and has a nice earthy smell. The best times to look for litter critters is in late spring and early fall, when the weather is still warm. Defrosting litter that has been sitting underneath snow may get you some invertebrates, but not as many as you’d find when its warm outside.

 

How much litter do you harvest? I recommend that you sample two cups of litter (that is, measure by volume). In this case, I raked up 2 cups of moist litter (its OK if some soil clings to it) and place it in the bowl to bring inside.

Back inside, remove the top portion of the berlese funnel, and gently scoop the litter from the bowl into the funnel. Some dirt and debris will fall through the mesh, so hold it over a trash can. When you have added 2 cups, gently nest the funnel back into the bottom half and move the lamp over the litter.

 

Berlese funnels work by gently heating the top of the litter creating a gradient of heat and moisture. Since most litter organisms like it moist, they will work their way down until they fall through the mesh. The larger ones will tumble into the alcohol. Some of the smaller ones may “stick” to the tapered part of the funnel, especially if water condenses on the inside.

When the litter is dry (usually about 24 hours) carefully lift the top portion away from the bottom (bump it and you may wind up with a dish full of dirt!). Do your best to pour off the litter into the trash (retrieve the screen!), then rinse the funnel into the dish to get any small things stuck to the side

            Author: Mike Kaspari
Last Updated: 31Jan2003:
                                     

This page was built with support from the National Science Foundation



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