I thought I would share just how exciting it is to be in a laboratory doing critically important work as an entomologist, processing pitfall trap samples. I’m kidding, of course, when it comes to the “exciting” part, but it truly is important.
The project I am involved with is striving to develop a protocol for assessing the ecosystem health of forested watersheds, a common yet complex habitat in the northeast U.S. The University of Massachusetts has partnered with the Massachusetts State Department of Environmental Protection and the United States Environmental Protection Agency to carry out this research. Dozens of people have been working in the field and in the lab for nearly ten years already. What started as one person’s project has mushroomed into something much greater. Ok, I know what you’re thinking: How does this affect me, Al Franken?
The habitat under scrutiny here includes many streams that run for most of the year, but run dry in the heat of the short summer. Hence, pitfall traps can be set in mid- to late July in places that are under water the rest of the year. Even then, a freak storm can set the watershed running again and flood the traps, or a beaver can dam the place and do the same thing. The former event happened last year, so I am able to process only a portion of the total pitfall trap samples collected in 2008.
A pitfall trap is a container sunk into the soil (or sand, or other such substrate) such that the lip of the container is flush with the surface of the substrate. Any insects, spiders, mites, and other creatures that come strolling by then fall into the trap. A trap is typically set for a week before being collected and the contents preserved in ethyl alcohol.
The resulting sample I see is in a plastic container with a label detailing the site identification and plot number, and date the trap was set and the date it was collected. Comments indicate the type of location (such as a sphagnum moss mound) and the condition the trap was found in when it was retrieved. I pick out the insects, arachnids, and other invertebrates that I can see with my naked eye, placing each taxon into its own glass shell vial. The vial is labeled both inside and out with the plot number, site ID, and taxon name (Coleoptera – beetles in this photo). The inside label also includes the number of specimens.
I also record the same data on a sheet, counting the number of specimens as I go. Once I’m done with the “big” specimens, I then put the container under the microscope and sort out the smaller things. The effect the alcohol preservative has on the specimens can be dramatic. Spiders fall apart. Even beetles start losing legs and abdominal segments. Springtails, normally pigmented, become literal shadows of their former selves, the alcohol having “cleared” them. It is a strange sight to see a ghostly springtail float across your field of view (cue the spooky music).
The amount of debris in a given sample, and/or the number of invertebrates, can greatly extend the time it takes to process a sample. It can also be very confusing at high magnification to tell a segmented plant part from an insect larva!
Stay tuned for further episodes in the life of an entomologist. Next week, Eric goes insane while trying to identify micro-Hymenoptera to family level….