Berlese Funnels to Sweep-netting

In previous posts, I may have talked excitedly about Berlese funnels, a technique to extract little critters from the leaf litter layer. I had just finished constructing eighteen of these contraptions when I discovered two small obstacles. First, the funnels fish out very, very little critters. From the first sample that I tried, I only first one or two insects that did not look like specks with the naked eye. The rest were around 1 to 2 mm and I needed to look at with a microscope. Second, herbivorous insects don’t scuttle in the leaf litter. They stay in the vegetation where there is more food and fewer frogs and lizards who want to eat them. So I was really surveying the community of itsy-bitsy decomposers rather than large herbivores, even though my question asked about how the herbivore community varied with fragment size and interior vs. edge. Oops.

So I needed to back up and start over. After consulting with a wonderful entomologist visiting Las Cruces, I decided just to sweep and beat-net. Very simple. Take a net. Sweep through all the vegetation, 30 strokes for a 16 meter squared plot then beat the understory vegetation into the net. That should more or less give me an idea about the kind of critters crawling (and hopefully eating) around in the vegetation. Along with katydids and grasshoppers, I collected quite a few spiders. These predaceous critters could give me an even better picture about the arthropod community composition.

Within each plot, I also assessed the herbivory level on and identified to family all the woody seedlings in a 1 m by 2 m area. This data should tell me if herbivory damage varies with fragment size or proximity to edge and if different types of seedlings grow in fragments of different sizes or near vs. far from the edge.

I collected all the samples in one feverish before flying back to the States. Never, never again will I let myself believe that all will go according to plan and that I have plenty of time to do anything my little heart desires. Now it is time for data entry and arthropod identification when I return to Grinnell this fall.