Fossil Beetles in Quaternary & Environmental Studies

BEETLES (COLEOPTERA) in
QUATERNARY STUDIES
at the Department of Geology,
Colby College

The study of subfossil beetles (Class Insecta, Order Coleoptera) is becoming an important tool in understanding past environmental change. Virtually any non-marine sediment that has identifiable organic remains will include remains of insects, and many of these will be beetles.

Remains that are frequently found and are readily identifiable include disarticulated [unattached] heads, pronota, and elytra. The first illustration at the right, of the ground beetle Schizogenius sulcifrons (family Carabidae) , shows these body parts. The sculptural elements that are the basis for much modern taxonomy are preserved and make the fragments frequently identifiable to the species level. Most beetles are quite specific as to habitat requirements, and those in non-island environments have undergone almost no evolutionary change in the Quaternary Period. We therefore can use their modern ecological requirements as a basis for interpreting what past environments must have been like.

For example, the second figure shows a modern specimen of the rove beetleLesteva pallipes (family Staphylinidae). Note the oblique light band on the elytron, indicated at the arrow. Below that is an individual left elytron of this species, one of over 1,000 identifiable fragments recovered by Heather Hall '90 from sediments deposited about 2000 years ago along the Sandy River, north of the Colby campus. Though the elytron is somewhat darkened, the oblique lighter band is still visible.

The next figure shows a modern habitat on the lower slopes of Mt. Katahdin, in north-central Maine, where specimens of Lesteva pallipes, as well as other species found in the Sandy River sediments, have been collected. (Click on the image for an enlarged view!)

Based on the insect assemblages present in the sediments, then, we can say that the pre-European settlement margins of the Sandy River very probably included environments like that shown at the left, although the modern river margins are much developed for agricultural uses and have been cleared of dense forest. Compare this habitat illustration with the view of the modern Sandy River margins shown in the close-up view in the bottom photograph.

For more detailed information on the use of beetles in Quaternary studies, check out Quaternary Insects and their Environments by Scott A. Elias; Washington, D.C.: Smithsonian Institution Press, Š1994; 284 p.

You can also find out more by connecting to any of these other Quaternary Beetle web servers:

Quaternary Entomology at North Dakota State University
Quaternary Entomology Dispatch [Q.E.D.] home page at U. of Colorado
Quaternary Entomology of Clarke Garry, U. of Wisconsin, River Falls
Bibliography of Quaternary Palaeoentomology

Eocene fossil insects from the Green River Shale