INTRODUCTION

The family Carabidae is one of the most successful groups of beetles. There is an estimated 40,000 species throughout the world (Ball 1979), most of them living in subtropical and tropical areas. In Canada, the group contains about 930 species (Bousquet 1991).

The Canadian fauna of carabids is well known taxonomically, thanks to the work of Wallis (1961), who reviewed the tiger beetles of Canada (tribe Cicindelini), and especially to the work of Carl H. Lindroth, who between 1961 and 1969 published the six parts of his series "The ground-beetles of Canada and Alaska". Consequently, virtually all adults living in Canada can be positively identified. The probability of finding an undescribed carabid species in the Ecozone is low compared with some other group of beetles, such as Staphylinidae.

The taxonomy of the family Carabidae is based exclusively on adults. The larvae are known for less than 10% of the North American species (Thompson 1977); in addition, many larval descriptions, mostly old ones, are poor and inadequate for comparative studies. Carabid larvae possess good structural features and could be use to test phylogenetic hypotheses based on study of adults (Goulet 1977).

Habitat requirements are known for most species living in Canada, as seen in the works of Lindroth (1961-1969) and Larochelle (1975). Some of the species occur in very specialized habitats, such as beaver houses (e.g. Pterostichus castor Goulet and Bousquet), while others live in a variety of habitats (e.g. the ubiquous Pterostichus melanarius Illiger). The vast majority of carabids occurring in the Mixedwood Plains Ecozone are terrestrial and live mainly in open fields, forests, along rivers, lakes, and ponds, and at the edges of marshes and bogs. A few species could be considered as subaquatic (e.g. Blethisa quadricollis Haldeman) or arboreal (e.g. Dromius piceus Dejean). Our knowledge of the biology of carabid species is fragmentary and in general insufficient. Mating behavior, oviposition behavior, larval and pupal developments, feeding preferences, and seasonal activities are some aspects of the biology that have been poorly studied in North America.

Members of the family Carabidae are in general of little importance as pests. Some species are known to feed on seeds of plants, such as oats, barley, wheat, corn, and parsley, but the damage done is usually not significant (Thiele 1977). The slender seed-corn beetle, Clivina impressefrons LeConte, and the seed corn beetle, Stenolophus comma Fabricius, are two carabids present in the Mixedwood Plains Ecozone known to do occasional damage to cultivated plants. The economic importance of Carabidae lies in their role as predators of other arthropods, since their prey often includes important pests in both forestry and agriculture. The most important in this respect are the species of the genus Calosoma that are voracious predators in both larval and adult stages. Adults of many species, such as C . scrutator Fabricius and C . frigidum Kirby, readily climb trees and are well-known control agents of caterpillars of many important lepidopteran forest pests, such as the saddled prominent, Heterocampa guttivitta Walker, and the forest tent caterpillar, Malacosoma disstria Hübner. Numerous species of many other genera of Carabidae are adapted to various agricultural habitats and may occur there in large numbers. In these habitats, they are not only important in keeping the herbivore/carnivore balance, but they also have great proven potential as bioindicators and for the control of pest species. Indeed, some species have been intentionally introduced into eastern North America to combat pests that have been accidentally introduced.

Adults of one species of Carabidae, the stink beetle, Nomius pygmaeus Dejean, which occurs in the Ecozone, are attracted to light and may become a real nuisance in dwellings due to their strong fetid odour. Fortunately, the species is rare throughout most of its range.

The family Carabidae is presently represented in the Mixedwood Plains Ecozone by 470 species. This number represents about 50% of the Canadian fauna. Of these species, 141 (30%) are found only in Canada in the Mixedwood Plains Ecozone only (see Table 1). There are no endemic species of Carabidae in the ecozone considered. Some species of beetles, for example Oxypoda demissa Casey, Canastota canadensis Casey, Acrotona adjuvans Casey, Trichiusa postica Casey in the family Staphylinidae, are at present known only from the Mixedwood Plains Ecozone but these species are likely more widely distributed. Their present distributional restriction is likely due to insufficient collecting and poor taxonomic knowledge of the group.

Among the carabids living in the Ecozone, members of the genera Cicindela Linné and Calosoma Weber are probably the most well-known to biologists. Adults of the genus Cicindela are often brightly colored, run rapidly, fly with great agility, and are among the most voracious and fierce beetles; they have earned the popular name of tiger beetles. Members of Calosoma are usually larger than average and, as stated previously, prey mostly on lepidopterous larvae including several species that are of ecomomic importance. The distribution of members of these two groups within the Mixedwood Plains Ecozone is summarized in Table 2.

Table of Contents

• ORIGIN

• INTRODUCED SPECIES

• TEMPORAL AND SPATIAL CHANGES: RECENT TRENDS

• CONCLUDING REMARKS and
  REFERENCES

• TABLE 1: LIST OF SPECIES FOUND IN CANADA ONLY IN THE MIXEDWOOD PLAINS ECOZONE

• TABLE 2: THE GENERA Cicindela AND Calosoma IN THE MIXEDWOOD PLAINS ECOZONE.

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