Insect Biomass Study Procedures

The Metchosin Foundation helps to fund a long-term study of Metchosin insect populations. The study, coordinated by University of Victoria’s Dr. Neville Winchester, will enter its third summer in 2020.

To measure the insect populations, sample insects are collected during the summer months at properties throughout Metchosin using Malaise traps (picture above).  The traps are tent-like structures that funnel flying insects into collection bottles.  The bottles are changed every two weeks. The bottles, filled with preservative, are then taken to a central location.  

During the winter months, after the traps have come down, the insects in the bottles are sorted, counted, and weighed. In 2018, 132,000 insects were collected.  The count for the 2019 collection is going on now. The expectation is that the count from the 2019 season will be much larger–perhaps 300,000 insects.

You may have seen the traps at some of their Metchosin locations. Metchosin Foundation supporters may be interested in the less visible part of the study–how the count actuallly happens. On January 31, Metchosin Foundation Director Kem Luther visited the lab at the University of Victoria where the insects are tallied.  Here is his account of the procedure

The 2019 bottles are stored on shelves. With 19 Metchosin trap sites and bottles being collected about every one or two weeks, approximately 245 bottles arrive at the lab over the course of the summer.

From the bottles, the insects go onto a special sorting tray under a dissecting microscope.  So far, most of the sorting–hundereds of hours of it–has been done by Dr. Winchester.

The insects are sorted into several broad categories and are moved to small containers for each category. Categories include moths, beetles, hymenoptera (ants, bees, wasps), and flies. A multiunit counter at the desk keeps track of the insects in each category.

Stacks of the smaller containers holding the sorted insects sit beside the counting scope.  As each container is used, a label is affixed to note its contents, collection date, and location.

At a later point, the sorted collections in the small bottles are taken to the sink and each one is put through a filter that removes the preserving liquid. They are left in the filter until the liquid is mostly gone, measured by the number of drops per minute coming out of the bottom of the container.

The drained insect mass is taken to a calibrated scale where it is weighed and the weight recorded.

Once weighed, the insects are rebottled. But this time they are moved to special archive bottles supplied by the BC Museum. New preserving liquid is added, the bottles are sealed, and special archival labels are affixed.  The Museum will become the long-term home for the collected insects, available to future researchers.

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