Monthly Archives: October 2010

Back in the lab: sorting the samples

From Terry Wheeler, McGill University:


Field work is the glamour event of projects like ours, but every good day of collecting generates a huge amount of work back at the lab. One of the lab rooms at McGill University’s Lyman Entomological Museum has been transformed into Sorting Headquarters for the NBP and that’s where most of our energy has been focused this fall. Almost every available inch of counter space in the room is lined with microscopes, lights, vials, sorting trays, and boxes of carefully arranged labels.

sorting tray

Tools of the trade

A study such as ours, with multiple collecting methods and sample sites, can collect enormous numbers of our target groups of insects and spiders, but those trap samples also come complete with many other insects, leaves, seeds, soil, dirt and more. That means that every one of the thousands of samples we brought back from the field must now be sorted at the microscope, to separate the spiders, flies, beetles, wasps and aquatic insects for our individual projects. Each sample is carefully divided up into separate vials for each of our target arthropod groups. It’s long and hard work – six weeks of field collecting means several months of sorting and processing samples – but this is our first chance to get a sense of how the patterns look across our sites. Even at this early stage we are starting to see differences between the Malaise traps from Moosonee (hundreds of horseflies), and pan traps from Kuglugtuk  (lots of specimens of an unidentified yellow fly that we don’t see in the eastern samples). The Lake Hazen samples are quick and easy to deal with (there’s not much diversity that far north), but a single Malaise trap from one of the boreal sites can take more than a full day for one of the students to sort through.

Tabanid tray

Horsefly soup: halfway through a sample

This sorting is just the first stage in processing our samples from Year 1. Once everything is sorted to order (spiders, flies, beetles and the rest), the second round begins. Each student will sort their own group of interest to finer levels of resolution – family, genus, species – as we move toward the species-level identifications necessary to see ecological patterns at fine scales. Many of the flies, beetles and wasps will be mounted on pins; the softer-bodied spiders and aquatic insects will stay in ethanol. Specimens preserved in ethanol will also be used for DNA barcoding, to unlock the genetic diversity of the northern arthropods.

Sarah at scope

Sarah tackles a sample

At our current pace, it looks like this first round of sorting will be wrapped up by the end of the fall term. Seeing that last bag of samples come out of the freezer will probably be a welcome Christmas gift for the Sorting Crew.