Most people tend to regard beetles as being secretive and possibly somewhat lethargic, but anyone observing beetles on a warm summer day will quickly realize that large numbers of species can move extremely rapidly both on the ground and in the air. In the section dealing with geological applications, we alluded to the fact that beetles were rapid colonizers and were well adapted to certain ecological niches. The climatic fluctuations of the Pleistocene forced beetles to move vast distances so that their present distributions are often quite dissimilar to their distributions during the Pleistocene. For example, the present Canadian insect fauna would only have been able to colonize most of Canada during the period following ice retreat. With the exception of the Yukon, parts of the Northwest Territories, possibly portions of the east coast of Labrador and some of the islands in the Gulf of St. Lawrence, ice retreat has taken place less than 15,000 years ago. Substantial portions of Quebec and smaller areas of the Northwest Territories were ice-covered as recently as 7,000 years ago. We can demonstrate this by illustrating four beetle species which have moved considerable distances during the Pleistocene.

Diacheila polita Falderman (a ground beetle) is today confined to the extreme northwest of Canada, with a range expanding westward through Alaska, Kamchatka and eastern Siberia, eventually terminating on the east side of the Kola Peninsula. This beetle is flightless and usually inhabits open peaty soil on the tundra. It has been found in southern Ontario in the Scarborough Formation, in the St. Lawrence Valley of southern Quebec, and in the period approximately contemporaneous with the maximum development of ice it was a common resident in the area west of the Michigan lobe in Illinois and lowa (Morgan and Morgan, 1982, 1986; Baker et al., 1986). The youngest reported date for the species in eastern North America is about 12,100 years B.R (Barnosky et al., 1988). Comments on the North American zoogeography of this species are provided in Morgan and Morgan (1980b, 1982) and Morgan (1987, 1988a). Figure 10 illustrates the known and postulated movement of the species through time in North America; Figure 11 shows the known modern range.

Helophorus arcticus Brown (a water scavenger beetle) provides a good example of the additional knowledge which has been gained since the original "Beetle Bits" paper was written in 1980. H. arcticus was first described by Brown (1937) and, in 1980, was only known from three modern collecting localities (Churchill, Manitoba; at Lake Harbour (Baffin Island) and at Hebron, Labrador). As a result of deliberate searches, the species was again collected at Churchill in 1983 and was found in northeastern Ungava Bay in 1986 (Figure 11). The ecology is not fully understood, but generally the beetle appears to be associated with granular littoral substrates at, or relatively close to, treeline. In all modern finds, the species is situated close to cold ocean water. The fossil record also indicates that it may have lived near cold water bodies in the form of large glacial lakes, meltwater spillway routes, or the sea. Fossil specimens of H. arcticus were first found in the Scarborough Formation of southern Ontario (Morgan, 1972), and later in possibly contemporaneous Early Wisconsinan deposits at Woodbridge, northwest of Toronto (Williams et al., 1981). It has subsequently been re-covered from localities outside the maximum Late Wisconsinan ice limit in lowa (Baker et al., 1986), as well as in post-glacial sequences in southern Ontario, Quebec and the Maritime Provinces (Mott et al., 1981; Morgan 1989). Recent publications (Smetana, 1985; Morgan, 1989) summarize what is known about this enigmatic species. H. arcticus and Diacheila polita have been recognized as beetles with contrasting colonizing potentials, and this has been expanded upon elsewhere (Morgan and Morgan, 1982; Morgan, 1987).

Anotylus gibbulus (Eppelsheim), a rove beetle, was found in supposed Sangamonian (last) Interglacial deposits at the Don Valley Brickpit (Toronto) in 1974. This species is of interest to entomologists because it is not living in North America (or even Western Europe) at present. The core area of A. gibbulus appears to be the Caucasus Mountains in Southern Russia. One other modern locality near Vladivostock has also been described (Hammond et al., 1979).

The reason for the contraction in range is not clear, because A. gibbulus was also present in Central England until approximately 35,000 years ago (Figure 11). It is possible that the range of this beetle (often associated with dung from large herbivores) may have been curtailed by the demise of the large mammals in latest Pleistocene time.

Aphodius holdereri Reitter (a lamellicorn beetle) is another species which is now living far from fossil sites of Middle Wisconsinan age. This dung beetle is exceptionally common in certain deposits of Central England. In spite of an extremely distinctive morphology, the fossil specimens were not matched to living counterparts until the early 1970s (Coope, 1973). The somewhat restricted distribution in the region of Tibet, north of the Himalayas, is a dry steppe environment which is probably similar to the open landscape envisioned along the major ice margins in Britain, Europe and North America .

Although we have only used four examples above, many more could be cited illustrating movements in distribution which amount to thousands of kilometres between fossil and modern loca-tions, even for relatively recent Late Wisconsinan sites. The reader is referred to publications on Cicindela (Morgan and Freitag, 1982; Nagano et al., 1982); Holoboreaphilus (Morgan et al., 1984); Blethisa (Morgan et al., 1986); Polygraphus (Morgan, 1988b) and Helophorus (Morgan, 1989) as examples of North American fossil and modern range comparisons. As this research area expands, it should be possible to further illustrate the movement of selected species, or even whole faunal assemblages through time and to reconstruct the shifts of beetle populations in front of the advancing and retreating Wisconsinan Ice Sheet.

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