Modern taxonomic keys rely heavily upon features seen on articulated specimens; the disarticulated fossil material has to be looked at in an entirely different way, often utilizing features which are obscured, or not readily apparent under the regular light microscope. In this respect the paleoentomologist can utilize shape and macro-ornamentation of various sclerites, and by using the petrographic microscope, examine micro-ornamentation at magnifications of about 150x. This type of analysis is particularly useful when looking at carabid (ground) beetles. The genus Bembidion, for example, includes over 150 species in Canada and Alaska (probably well over 400 species in North America) which can often be recognized to sub-generic level by gross morphological features, and then narrowed considerably by the examination of micro-ornamentation.

One of the most powerful tools in this respect is the scanning electron microscope. The first SEM photographs of fossil beetles were taken at the University of Birmingham (Morgan, 1969, 1970). Detailed comparison of fossil and modern weevils of the same species revealed identical features at high magnifications. Besides revealing details of beetle microsculpture, the SEM is also capable of illustrating the remarkable preservation of parts which remain articulated in fossil specimens. The SEM is still used today for illustrating specific fossil fragments, but pre-treatment may damage rare specimens (e.g., fragments which tend to charge readily and often must be coated). Colour patterns cannot be seen under the SEM, and photomicrographs are difficult to compare to specimens photographed under the light microscope because of the detail revealed by the SEM. Undoubtedly innovations, such as environmental chambers and low Kv operation, will allow more frequent use of this technique. We frequently use antistatic solutions and carbon coating to reduce charging, and to keep the specimen in a more natural state.

The key characters for a species, recognized by all modern taxonomists, are the beetle genitalia. All fossil abdomens are carefully dissected to see if they have retained the genitalia. Unfortunately, this search is often unsuccessful; the specimen may be female, parthenogenetic, or the genitalia have been lost. One particularly well-preserved example recovered from material in a borehole at Parkhill, Ontario, at a depth of 9 m. Associated organic detritus has been dated at 10,870 + 90 years B.R (WAT-376). After comparison with modern specimens the aedeagus was identified as Gyrinus bifarius Fall, a species found in the boreal zone of North America.

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