As Coope (1970, 1979) has frequently pointed out, a large number of beetle species are quite specific about their living requirements. For example, scolytids (bark beetles) are often restricted to certain types of trees, frequently oc- cupying specific locations on the tree under attack, e.g., the lower bole and root region or the mid-portion of the bole, or the growing tips of branches. Certain scarabaeids (dung beetles) are confined to the dung of specific animals. Other species from different families have only been collected in specific habitats such as beaver lodges. Many carabid (ground) beetles have decided preferences for different types of substrates, often having modified sclerites to take advantage of differing lithologies. Finally, many phytophagous (plant-eating) beetles, representing a number of families, utilize specific host plants, although they frequently are not present over the whole range of the plant species, but often stop as though confined by certain climatic factors (Morgan, 1970) .

There are, of course, many species of beetles whose ecological requirements are very poorly understood, and also large numbers which are eurythermic, extending in Europe from the Mediterranean coast to North Cape, and in North America from the Gulf of Mexico to the Tuktoyaktuk Peninsula. Nevertheless, two important principles have been established by an examination of a large number of fossil faunas:

Ecological assemblages have remained relatively constant through time with groups of genera and species apparently occupying the same niches for hundreds of thousands, or even millions of years; and beetles appear to be rapid colonizers and are able to take advantage of their mobility and position in the food chain to move quickly into a region once conditions become suitable for life.

For example, in recently deglaciated terrain, carnivorous beetles can prey upon spiders and flies, which in turn depend upon lichens or algae for sustenance. In this way, they are not dependent upon higher plants which in turn are often restricted from moving into a region because of unsuitable substrate development.

Perhaps the most remarkable use of these principles has been in the English Midlands where a short-lived, but intense, warmer episode punctuated the Siberian-like cold of the Middle Devensian (Middle Wisconsinan / Weichselian). One locality, a small gravel pit at Four Ashes near Wolverhampton, produced a number of organic lenses which revealed deposition from the last (Ipswichian/Sangamonian) Interglacial through to the late Devensian (A.V. Morgan, 1973). More importantly, the Four Ashes sequence indicated the presence of a thermophilous insect fauna between faunas which contained Scandinavian and Siberian species (Morgan, 1970, 1973). Microhabitat and microclimatic differences could not be readily invoked, since the substrate was the same for all the sites, and since they were all deposited within an area of some 400 m by 200 m in relatively flat terrain (vertical amplitude less than 5 m). This observation verified the results of a number of other sites of similar ages, but found in scattered geographic locations. These data, along with data from other areas, were incorporated in a paper on climatic re-construction of Central England in Middle and Late Devensian times (Coope et al., 1971). The preliminary climatic curve shown in this publication was modified by subsequent research (Coope, 1975, 1977). The beetles changed from arctic boreomontane species, to thermophilous species largely representative of the North German plain (i.e., warmer than southern England), and then reverted once again to treeline - tundra species. Other remarkably rapid shifts in insect faunas have been recorded from late-glacial (Late Wisconsinan) sites in many different parts of the British Isles (Coope, 1977), but our work in southern Ontario has not yet produced a similar continuity of the climatic record. Rather, we have established isolated points for a climatic curve, and such examples are discussed below.

The first locality is the long-famous Sangamonian site of the Don Valley Brickpit. For about a century, the Don Formation has been examined for its warm climate flora and the fossils of beetles, which have remained both generically and specifically unidentified. We have examined and identified a small fauna which shows that the insects reflect a climate which is almost identical to that of Toronto today. The presence of a diverse group of beetles and associated caddisflies (Williams and Morgan, 1977) indicates a mixed deciduous and coniferous woodland bordering a well-vegetated, slowly moving river flowing into a lake with a water level well above that of the present day Lake Ontario. The July average temperature would have been about 20 - 21 degrees C. A site with similar climatic implications, and possibly of the same age, has also been described from the region southwest of Kitchener-Waterloo. The Innerkip site (Pilny and Morgan, 1987) has a moderately well-preserved beetle fauna with species (not recorded elsewhere until the early Holocene) in common with the Don. Many of the species from the Innerkip site today only reside in southern Ontario. The second locality to the east of Toronto, referred to earlier in the historical discussion, is at the Scarborough Bluffs. An insect fauna recovered from the lower part of the Bluffs indicates a vastly different climatic regime from that of the Don. The Scarborough Formation, of Early Wisconsinan age, rests on top of the Don Formation (Karrow, 1967; Karrow and Morgan, 1975). Insects collected from the deltaic Scarborough Sands and the lacustrine Scarborough Silts and Clays are typical of the northern boreal forest or open tundra, close to treeline. The habitat reflected by the insects appears to be a patchy spruce environment with open ground areas. The July average temperature would have been about 11-12 degrees C.

Although the thermal environments of the Don and Innerkip, and Scarborough, sites were drastically different, we cannot interpret the rapidity of change which took place during the deposition of the sequences since it lies beyond conventional radiocarbon dating. It would be fascinating to have good data from the terrestrial record on just how rapidly the climate of the last interglacial deteriorated; a prospect which may await us in the not so distant geological future. Such knowledge would present vital information for our species and would have an incredible fiscal impact on industries and governments who are currently trying to come to grips with the economic and social realities of global change.

It is equally interesting to examine the poorly preserved insect faunas of the Early and Middle Wisconsinan and to contemplate the long timeframes with far more severe climates which are indicated by tundra insect assemblages in southern Ontario. (Morgan, 1972; Warner et al., 1988). The prospect of increasingly harsh climates, the disappearance of deciduous trees, followed by conifers and the advent of a bleak tundra with active permafrost and a slowly advancing ice sheet is one which can only be welcomed by Alberta and OPEC! Such information would also be invaluable in helping address possible counterbalances to the predicted atmospheric warming suggested in various Global Circulation Models (GCMs) in respect to the "greenhouse effect".

Recent concerns about the rapidity of carbon dioxide buildup, and the potential implications of climate warming have led to renewed interest in understanding the proxy data record preserved in Quaternary sediments. Most research has been conducted by palynologists, and unfortunately the beetle record seems to have been overlooked by many. Nevertheless, it was over twenty-five years ago, in 1970, when the British Quaternary Association discussed the perceived climatic ameliorations of latest Pleistocene time at the University of Birmingham. Out of those discussions came the realization that there had been very rapid climatic ameliorations at ca. 13,500-13,000 years B.R and at 10,200 years B. R (Coope et al., 1971; Coope and Brophy, 1972). These movements were later shown to be caused by fluctuations of the polar front in the North Atlantic, but they had been detected in the coleopteran record despite relatively complacent records in the pollen stratigraphy from sites of similar ages. The Allerod/Dryas fluctuations are, of course, recorded in pollen sequences in western Europe, and, more recently, believed recorded in eastern Canada (Anderson, 1983; Mott et al., 1986).

Oscillations in pollen spectra in Ohio and Indiana (Shane, 1987) attributed to a "Younger Dryas" effect in the mid-continent are not matched by climatic fluctuations in the beetle records nor are they matched by the oxygen isotope record (Fritz et al., 1987). The oxygen isotope records in western Europe clearly reflect the movement of the polar front (Eicher and Siegenthaler, 1976), and one must look for another explanation for pollen spectral shifts in the North American continental interior. Morgan et al. (1982), Morgan, (1987) and Fritz et al. (1987) have suggested that such shifts are not connected to regional climatic change, but rather due to lake effects. We now understand that these are likely attributable to discharges of cold glacial meltwater, and these, in turn may have triggered movements in the polar front in the North Atlantic.

With few exceptions (Elias, 1985; Morgan et al., 1985; Schwert and Ashworth, 1985; Nelson and Carter, 1987) Holocene insect sites have not yet been examined in any great detail, but there is much to be done. Insect preservation in these younger sites is generally good to excellent, the sites can be well dated and undoubtedly there is much to be learned in terms of zoogeography, archeology, and climate reconstruction.

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