chapter1 acg taxonomy 16

Chapter 1Grasslands and Grassland Arthropods of Canada1

Joseph D. ShorthouseDepartment of Biology, Laurentian University

Sudbury, Ontario, Canada P3E 2C6

David J. LarsonBox 56, Maple Creek, Saskatchewan, Canada S0N 1N0

Abstract. Grasslands are areas dominated by grasses and herbaceous vegetation and with few or no trees. They are generally open and contiguous and are widely distributed across Canada from the Yukon to eastern Ontario. The largest grasslands are those of the Prairies Ecozone, which extends from the CanadaUnited States border in a triangle from the western edge of Alberta to the eastern edge of Manitoba. This ecozone comprises the northern extension of the Great Plains of North America. This chapter provides an overview of the geography and biota of the Canadian Prairies Ecozone.

Canadas prairies were covered by several continental glaciations that resculptured the surface topography and kept biotic communities in a state of flux. Thus, the current grasslands of the Canadian prairies are the product of environmental stresses, including a varied continental climate, low and variable precipitation, fire, and biotic pressures such as grazing by herbivores. The arthropods that developed here are mostly species that are tolerant of environmental changes.

The first humans to arrive on the Central Plains about 10,000 years ago were low-impact hunter-gatherers. Europeans arrived about 150 years ago with technological agriculture and quickly settled throughout the prairies. The once extensive native grasslands were reduced to small fragments, and alien species now dominate or occur in most regions. Most of the arthropod fauna seems to have survived these radical changes, probably due to its members being widely distributed and adapted to unstable and stressful environments.

Insects, spiders, and mites are the most diverse and abundant animals in native grasslands, are important in the functioning of grassland ecosystems, and occupy a wide array of niches. Grassland insects in Canada are adapted to cold winter temperatures, a short summer growing season, drought, and strong winds. Grasshoppers are particularly well adapted to grasslands.

Rsum. Les prairies sont des zones domines par les gramines et dautres plantes herbaces, et o les arbres sont rares ou absents. Elles sont gnralement dgages et contiges, et sont largement rparties au Canada, du Yukon lest de lOntario. Les plus vastes se trouvent dans lcozone des prairies qui stend en triangle au nord de la frontire amricaine, de la limite occidentale de lAlberta la limite orientale du Manitoba. Cette cozone est un prolongement vers le nord des prairies herbagres des grandes plaines dAmrique du Nord. Ce chapitre prsente un aperu de la gographie et des biotes de cette cozone.

Les prairies canadiennes ont travers plusieurs priodes de glaciation continentale qui ont modifi leur topographie et stimul lvolution des communauts biotiques. Leur tat actuel est le produit de divers facteurs de stress environnemental, y compris un climat continental vari, un rgime de prcipitations faibles et variables, les incendies et des pressions biotiques comme le broutage par les herbivores. La faune darthropodes qui caractrtise la rgion sont surtout des espces tolrantes de changements environnementaux.

Les premiers humains qui sont arrivs dans les plaines centrales il y a environ 10 000 ans taient des chasseurs-cueilleurs dont lempreinte sur le milieu naturel tait faible. Les Europens sont arrivs il y a environ 150 ans et ont rapidement colonis lensemble de la rgion en y pratiquant une agriculture technologique. Les

1 This introductory chapter is dedicated to Dr. Ruby I. Larson, who introduced both authors to the world of prairie insects in the late 1950s when we were in our early teens and members of her Junior Science Club of Lethbridge. Her mentorship and enthusiasm led to us both developing careers in entomology.

Shorthouse, J. D. and D. J. Larson. 2010. Grasslands and Grassland Arthropods of Canada. In Arthropods of Canadian Grasslands (Volume 1): Ecology and Interactions in Grassland Habitats. Edited by J. D. Shorthouse and K. D. Floate. Biological Survey of Canada. pp. 1-24. 2010 Biological Survey of Canada. ISBN 978-0-9689321-4-8 doi:10.3752/9780968932148.ch1

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2 J. D. Shorthouse and D. J. Larson

vastes prairies naturelles ont t fragmentes en petites parcelles, et la plupart des rgions sont dsormais peuples despces vgtales exotiques parfois dominantes. La plupart des arthropodes ont semble-t-il survcu ces changements radicaux parce quils taient probablement dj largement rpandus et adapts des environnements instables et rigoureux.

Les insectes, arachnides et acariens sont les animaux les plus diversifis et les plus abondants des prairies naturelles; ils jouent un rle important dans le fonctionnement des cosystmes des prairies et occupent une grande varit de niches. Les insectes des prairies canadiennes sont adapts aux hivers froids, aux saisons de croissance estivale courtes, aux scheresses et aux vents forts. Les criquets sont particulirement bien adapts ce genre de milieu.

Introduction

Grassland ecosystems cover approximately 25% (33 million km2) of the planets surface, a larger portion of the Earths land surface than any other vegetation type (Shantz 1954; Brown 1989; Meyer and Turner 1992). They represent one of the Earths major biomes and are one of the most productive and diverse terrestrial ecosystems. Common features found among grasslands include climates with periodic droughts, frequent fires, occurrence on landscapes that are level to gently rolling, low temperatures for part of the year, and an abundance of grazing animals (Anderson 2006). Grasslands contain few trees or shrubs and are dominated by grasses (members of the family Poaceae), which escape the deleterious impact of these features by having growing tips beneath the soil surface such that they are not exposed to desiccation and cannot be damaged by surface-feeding herbivores. Non-graminoid herbaceous species called forbs, many of which are found in the sunflower (Asteraceae) and pea (Fabaceae) families, are also common in grasslands (Anderson 2006). Thus grasslands are restricted to areas where water availability falls below the requirement for trees but is sufficient to support grasses. In many of Canadas grasslands, shrubs provide the only woody plant component.

Native grasslands are the largest vegetation biome in North America, and before the continent was settled by Europeans, grasslands covered about 162 million ha (Samson and Knopf 1994). They constitute a relatively continuous and roughly triangular area that extends from southern Alberta, Saskatchewan, and Manitoba south through the northern, central, midwest, and southern states of the United States to northeastern and central Mexico (Gauthier et al. 2003). This area is the widest latitudinal range of any North American ecological region, with North American grasslands representing about 710% of the worlds grasslands (Gauthier et al. 2003).

A variety of conditions affect the extent, permanence, and vegetation composition of grasslands in Canada. They merge into northern forested sites through a continuum of vegetation types that include increased proportions of broad-leafed and woody plants and are described by such terms as parkland and open forest. Grasslands also merge into arctic and alpine, marsh, fen and bog, and desert-like habitats. Grassy habitats may occur and persist over long periods in an early successional stage, usually maintained by a disrupting factor, or in a climax-like stage with a stable assemblage of flora and fauna. Many abiotic and biotic factors have been responsible for the history and sustainability of the grasslands in various parts of Canada. However, this introductory chapter is mainly devoted to the history of the grasslands of the three prairie provinces. We also provide a brief overview of prairie insects and describe some of their habits and adaptations.

The term prairie is the most frequently used to describe grasslands in Canada, whereas the term steppe is commonly used for similar habitats in eastern Europe and

Grasslands and Grassland Arthropods of Canada 3

western Asia. The prairies of Canada and the adjoining United States support rich and highly specialized communities of plants and animals in their native state that evolved in response to a variety of stresses, including drought, grazing, fire, erosion, deposition, soil disturbance, and decomposition (Anderson 2006).

Classification of Canadas Grassland Ecosystems

Ecologists have traditionally divided grasslands in North America into three sectors based on the height of the native grasses, which is a function of annual precipitation. According to Anderson (2006), these sectors are western shortgrass prairie (260375 mm precipitation), eastern tallgrass prairie (6251,200 mm precipitation), and mid- or mixedgrass prairie (375625 between the two). Shortgrass prairie is dominated by grasses that are 0.30.5 m tall, mixedgrass prairie is dominated by species that are 0.81.2 m tall, and tallgrass prairie is dominated by grasses that are 1.82.4 m tall. However, in the 1970s and 1980s, the Canada Committee on Ecological Land Classification established a different system to classify and map terrestrial ecosystems. This system delineated and described ecologically distinct areas of the countrys surface at different levels of generalization by various abiotic and biotic factors. Fifteen major ecozones were identified that in turn were subdivided into ecoregions (Ecological Stratification Working Group, 1996). Ecozones are large areas wherein organisms and the physical environment endure as a system and are delineated by a particular combination of climate, landforms, soils, water features, flora, and fauna. Ecoregions are characterized by distinctive large-order landforms or assemblages of regional landforms, small-order macro- or mesoclimates, flora and fauna, soils, water, and regional human activity patterns and uses.

Six of Canadas ecozones have grasslands and each is discussed in this book. The largest grassland areas occur on the prairies and in the interior of British Columbia (Fig. 1). The Prairies Ecozone covers most of Alberta, the lower half of Saskatchewan, and western portions of southern Manitoba, with remnants that extend into the Northwest Territories and the Peace River region of British Columbia. The Aspen Parkland Ecoregion of this ecozone is a transition region where the southern grasslands gradually merge with boreal forests to the north. The grasslands of south-central British Columbia (Fig. 1) occur in five of the ecoregions within the Montane Cordillera Ecozone and are discontinuous. Small areas of grasslands also occur in the Mixedwood Plains Ecozone of southwestern Ontario.

Geological History of Grasslands

A popular account of the geological history of the area that now comprises the Canadian prairies was provided by Storer (1989), the source of most information presented here. About 1,800 million years before present (mbp), the continental crust, beneath what is now western Canada, was uplifted to produce a range of mountains that partially extended through Saskatchewan and Manitoba. This range was eroded to an area of low relief over the following 100 million years, thus ending Saskatchewan and Manitobas history as an alpine area. Uplift and erosion stripped off surface rocks to expose igneous intrusions, granites, and metamorphic rocks of the Canadian Shield formation to the north. Since 590 mbp, a succession of thin sediments, mostly deposited in intermittent shallow seas, was laid down across the Great Plains to cover the eroded mountain belt in the southern parts of the region.

The current prairies were covered by warm shallow seas during the Paleozoic Era (543 to 250 mbp), when economically important deposits of petroleum and potash were formed.


The Paleozoic was bracketed by two of the most important events in the history of animal life. At the beginning of the era, multicelled animals underwent a dramatic explosion in diversity, with almost all living animal phyla appearing within a few million years. At the other end of the era, the largest mass extinction in history eliminated approximately 90% of all species of marine animals. During much of the Mesozoic Era (about 250 mbp), the Great Plains were covered by shallow seas that produced horizontal deposits of marine origin. Traces of this sea can be seen wherever erosion has laid bare ancient sea beds, such as along deep river valleys and in coulees where layers of fossilized shells of marine molluscs are common (Matthews 1979). The Cretaceous Era (about 145 to 65 mbp) is usually noted for being the last portion of the Age of Dinosaurs, but new kinds of dinosaurs appeared as well. Many insect groups, modern mammal and bird groups, and the first flowering plants arose during this time.

The Rocky Mountains began their uplift about 65 mbp. Sediments from these mountains washed eastward to raise the level of the plains. The mountains blocked moist air from the Pacific Ocean to create arid conditions. Large herbivores such as horses, camels, and rhinoceroses evolved on the plains 1425 mbp. These early grasslands were also covered with forests during wetter periods.

About 2.5 mbp, a cooling trend led to four glacial periods, with continental ice sheets over 1-km deep covering nearly all of the prairies. When glacial ice began to appear, the

Fig. 1. Map of Canada showing the location of major grasslands in green.


dry climate of the plains precluded the regional development of ice. Instead, the ice built up in adjacent areas and flowed onto the prairies. Each glacial advance obscured the effects of previous glaciations; thus, most of todays surface features date from the retreat of the last glacier, which began about 20,000 years before present (bp). The most recent Ice Age, called the Wisconsin, dates back at least 50,000 years (Williams et al. 1998). Only in the last 10,000 years has vegetation returned to a land that was once essentially a vast ice field (Barnosky et al. 1987).

Glacial ice covered all of the prairies during the Wisconsin, except for elevated areas south of Wood Mountain in Saskatchewan and the Cypress Hills plateaux in southeastern Alberta and southwestern Saskatchewan (see Chapter 2). Biota of the Canadian grasslands, adapted to warm summers, moved to refugia south of the ice cap for the preceding 40,000 years (Matthews 1979), facilitated by the low-relief lands of the mid-continent. Because most of the land in North America south of the ice cap and north of the southwestern deserts was covered by spruce-dominated forest during this period, it has been assumed that glacial-era grasslands were confined mostly to the Gulf Coast, to the Southwestern deserts, or to the south slopes of the southern Rocky Mountains (Ross 1970; Pielou 1991).

Two ice sheets affected the Canadian prairies during the Wisconsin (Pielou 1991). The Laurentide ice sheet eventually covered nearly all of the Canadian prairies. The Cordilleran ice sheet formed to the west of the Rocky Mountains and flowed east to the western edge of the prairies. Scientists do not know whether the two ice sheets were in contact, but an ice-free northsouth corridor may have existed east of the Rocky Mountains during some part of each glacial period (Mott and Jackson 1982).

During glacial advance, fluting fields were cut and drumlins and eskers formed under the ice. Other surface features came about during glacial melting when sediments in the ice were left behind or carried off the ice front in meltwater. Silt to cobble-size particles were swept away by rushing water and deposited in stratified outwash or till plains, or built up at the ends or sides of the ice to form non-stratified moraines. Strong winds over the melting ice surface and along the ice front drifted and sorted loess and sand and in places produced dunes of sand or silt (Grambo and Gjetvaj 2007) that remain to this day (see Chapter 3). Stratification of deposits had profound ecological effects, for coarse soils often do not hold water, whereas adjacent silty or clayey soils hold water and support lusher vegetation. Moraines occur as single or multiple ridges parallel to the ice front and as pitted terrain producing pothole topography. Potholes, or kettle holes, formed in moraines when blocks of glacial ice became buried. The melting of these blocks left depressions surrounded by low hills or knobs (see Chapter 2).

As the Laurentide ice sheet advanced from, and then retreated to, the northeast, it blocked water drainage to form a series of large glacial lakes. These lakes occupied depressed areas abutting the ice and persisted until channels were formed to drain the water. Glacial lakes filled with fine sediments so that their basins formed the flattest areas of the prairies, such as that around Winnipeg, Manitoba. The organic-rich clays of ancestral glacial lakes provide rich agricultural soils. Lakeshore areas exposed to wave action and wind have sorted soils, and seasonal ice action caused cobbles and boulders to accumulate along old beach lines.

Damming in the southern part of the glaciated area deflected water south toward the Mississippi River. Deep channels were cut where glacial meltwater ran freely or where ice front lakes drained, resulting in the large valleys and coulees that today dwarf the erosional capacity of the streams that now occupy them (Lewis and Anderson 1989). Variation


in soils, relief, moisture patterns, and aspect in these coulee systems produce the areas of highest habitat diversity within the prairies (see Chapter 2). Although many glacial features have been obliterated by erosion or concealed by vegetation, they nevertheless underlie the structure of these northern grassland ecosystems. Once the ice sheets melted, the drainage pattern was to the northeast into Hudson Bay or to the north (McPhail and Lindsey 1970).

Melting of the ice was accompanied by major climatic changes (Ritchie 1987), which permitted vegetation to expand northward into areas thickly mantled with glacial debris, especially sand and wind-borne silt. It was not until at least 1,000 years after glaciation that spruce (Picea spp.) recolonized eastern Canada (Hamilton and Langor 1987), and a similar lag may have occurred on the prairies. However, a black spruce (Picea mariana (P. Mill.))-dominated forest came to occupy the area vacated by ice, with evidence of tundra preceding the forest and perhaps more steppe-like conditions in the drier western part of the plains.

About 10,000 years bp, the southern part of the spruce forest was replaced first by deciduous forest, and then by grass in the east and directly by grasslands in the west as a warming period (known as the Altithermal or Hypsithermal) began (Anderson et al. 1989; Anderson 2006). Between 7,500 and 6,000 years bp, the climate was warmer and drier than at present and the prairie extended farther north; then about 3,000 years bp, a major southward extension of boreal forest took place. In the northeast, tallgrass prairie replaced forests of oak and hickory during the warm and dry Hypsithermal, which was accompanied by an increase in fires, beginning about 8,000 years bp and ending 5,0003,500 years bp. Today, grasslands near the Mississippi River and northeastward have become increasingly favourable for trees and only relic patches of grasslands remain. This area of relic grasslands, which extends into southern Ontario (see Chapters 8 and 9), is called the prairie peninsula (Transeau 1935). During the Hypsithermal period, refugia from drought also existed within the expanding grasslands, most notably plateaux such as the Cypress Hills (see Chapter 3), which were high enough to intercept precipitation and cool enough to reduce evapotranspiration to a level that coniferous forest and associated biotas could survive. Grasslands reached their northernmost limits in western Canada during the Hypsithermal and have subsequently pushed south, but not without also leaving isolated northern refugia, most notably in the Peace River area (see Chapter 3).

An intriguing aspect of the glacial period is the relationship between the Laurentide and Cordilleran ice sheets (Rutter 1980). If they did not contact, or were separated at least during ice retreat, the area between them would have provided an ice-free route extending far to the north and contiguous with the refugial area of the central Yukon and Alaska (Pielou 1991). During glacial maxima, sea levels were lower and a land connection existed between Asia and North America across the Bering Land Bridge, which allowed passage of terrestrial biota (Harrington 1980; Hopkins et al. 1982). On the North American side, exposed land was limited to a rain-shadow-formed, ice-free refugial area in central Alaska and the Yukon. This was a smaller area and more remote from the main continental ice-free area of North America than was its counterpart in Asia. Thus, the movement of biota was primarily from the geographically larger and presumably biologically more diverse Palearctic to the Nearctic, although exchanges did occur in both directions. Organisms crossing the land bridge from Asia were held in the Yukon refugium until sea levels rose following glacial melting, cutting off the land bridge while opening the LaurentideCordilleran corridor to allow the biota to disperse to the Central Plains (Hopkins et al. 1982).


The importance of the Asia to North America route to Canadas grasslands is seen in the history of bison (Guthrie 1970, 1980). Although they are the premier symbol of the primordial prairies, bison are newcomers to North America, with the first arrivals about 400,000 years bp giving rise to the extinct giant bison (Bison latifrons (Harlan)). A subsequent wave of bison immigrants occurred at about 200,000 years bp, which introduced another form. A third wave at the end of the Wisconsin glaciation replaced and/or hybridized with the then existing plains bison to produce the modern B. bison L.

The Prairie Environment

The climate of Canadas prairies, described by McGinn (see Chapter 5), is mainly influenced by their location in the heart of North America with the Rocky Mountains to the west, which impede access of moisture-bearing winds from the Pacific. The result is a continental climate, subhumid to semi-arid, with short hot summers, long cold winters, low levels of precipitation, and high levels of evaporation (Hare and Thomas 1979). There are no major relief features on the prairies that influence climate, other than the Cypress Hills in Alberta and Saskatchewan (see Chapter 3) and a series of small hills along the Manitoba escarpment. Warm, moist air masses occasionally move north from the southern United States onto the southern prairies in early summer to cause significant rains, thunderstorms, and occasional tornadoes.

High winds are characteristic of the prairies. They exacerbate summer dryness and whip winter snow into blizzards and drifts. High winds also accelerate the evaporation of water, leading to water deficits. Wind erosion blows soils away from the tops of hills in southern Alberta and Saskatchewan and keeps sand dunes active, such as those in the Great Sand Hills of Saskatchewan (see Chapter 3). Summer thunderstorms are often accompanied by high winds, and south-central Alberta is reputed to be one of the worst hailstorm belts in North America.

Highly changeable weather is common (Chakravarti 1969), with large variation in temperature, wind, and precipitation on a daily, seasonal, and yearly basis. This pattern partly reflects the prairies high latitude, high elevation, and rain-shadow position, but also the prairies broad expanse, topographical features, and variations in airflow patterns. Outbreaks of arctic air may produce frost at any time on the prairies, and the biota must be able to tolerate the stresses caused by this variation. Species of plants and animals with the widest distributions and good dispersal abilities are best able to exist here.

Precipitation increases across the prairies toward the north and east, so that the transition from shorter to taller grasses, and then to trees, curves southward from central Alberta, across west-central to southeastern Saskatchewan, and into southwestern Manitoba. However, the evapotranspiration potential exceeds summer precipitation such that it does not appreciably contribute to soil water reserves or runoff. Streams, ponds, and lakes receive water that has been stored in the soil in late fall and early spring, or as snow during winter, so that with spring melt, there is a short period of excess moisture with over-surface flows and pooling in depressions. Nearly all streams that flow out of the area are fed from water sources outside the grasslands (for example, the Saskatchewan and Milk rivers and their main tributaries all originate in the Rocky Mountains). Standing waters, or lentic habitats, are extraordinarily productive. They may take the form of short-lived vernal pools, seasonal sloughs, more or less permanent lakes, or fresh water to variously enriched or even saturated brine. Extreme conditions of impermanence or salinity (see Chapter 3) often are associated with a uniquely adapted and endemic biota.


The prairies are usually cold and snow covered most of the winter, but irregular incursions of warm Pacific air across the Rocky Mountains, known as chinook winds, produce significantly warmer winter temperatures and often snow-free conditions in southern Alberta and southwestern Saskatchewan. Chinooks relieve the winter cold, but they are fickle and can appear and disappear within hours. Although bare ground and periodic warming favour many birds and mammals, the extreme temperature fluctuations and drying effects of chinook winds are deleterious to many plants and possibly insects that have winter dormancy.

Climatic conditions on the prairies favour grasses, but grass dominance is also aided by fire and grazing by large mammals. Grasslands produce an overburden or thatch of dead grass that tends to accumulate because decomposition is slow under dry conditions. Thatch provides fuel for fire, which was a frequent occurrence on the pre-settlement prairies (Collins and Wallace 1990; Anderson 2006). Perennial grasses and forbs survive fire better than do woody plants; thus frequent fires drove back forests and allowed expansion of grasslands. Wildfires were less frequent on the western prairies, where dry conditions produced less fuel such that drought was a more significant determinant of vegetation distribution.

Grasses in general are well adapted to withstand grazing. The grazed above-ground leaves are more or less expendable, whereas the growing tips and the persistent crown and roots are low and less easily grazed. The prairies once had a rich fauna of grazing animals, most notably the vast herds of bison (Knapp et al. 1999), which had a major effect on the vegetation (see Chapter 2). MacEwan (1995) reviewed some of the population estimates, which were as high 50 million animals.

Human Influences on the Grasslands

Humans have altered ecosystems on the Canadian prairies since the waning days of the Ice Age (Turnbull 1979; Finnamore 1992; Potyondi 1995; Radenbaugh and Douaud 2000). Humans arrived in the interior of North America by 14,000 years bp, probably having crossed the Bering Land Bridge during the Wisconsin maximum (Goebel 1999). Early humans would have had little effect on the environment; however, by about 10,000 years bp, a large portion of large mammals such as giant sloths and mammoths became extinct. The coincidence of this sudden die-off with the arrival of Clovis hunters has led to speculation that they caused the extinction of these large mammals (Martin 1989). However, other researchers have argued that humans were not equipped and their population was too low to cause such extinctions (Pielou 1991). The surviving species, essentially the modern mammal fauna, and indigenous peoples coexisted until European settlement.

When Europeans arrived on the Canadian plains in the 1800s, there were an estimated 30,000 native people. They were nomadic hunter-gatherers and bison were central to their lives, providing their main source of meat and shaping their spiritual beliefs (Guthrie 1980; Potyondi 1995). These early people did not farm, as bison would have eaten or trampled their crops. Fire was used for hunting, creating pasture for game species, and decreasing the abundance of woody plants (Anderson 2006).

Some of the first detailed records made in the southern parts of prairies were by John Palliser in his expedition of 18571860 (Potyondi 1995). Palliser travelled from the Red River Colony in southern Manitoba to the plains south of the North Saskatchewan River and mountains of western Canada. He was accompanied by a geologist and a naturalist who collected plants, and together they described the flora and fauna and potential for


settlement. The semi-arid lands near the USA border became known as Pallisers Triangle as a result of their findings.

Many Europeans initially headed west in search of bison, which they hunted to near extinction by the 1870s (MacEwan 1995). This coincided with the extirpation of prairie populations of bison predators (plains grizzly bear, prairie wolf, and mountain lion) and other large ungulates, including elk and pronghorn antelope (Potyondi 1995). Huge, open range ranches were established that operated for a short time until a combination of weather (especially the winter of 19061907) and greater settlement brought an end to the open plains (Stegner 1962).

Settlement resulted in the fencing of property, which indirectly resulted in the deterioration of range conditions caused by overgrazing of fenced pastures. Homesteading, sod busting, and cultivating on most of Canadas prairie occurred from 1908 to the 1930s (Potyondi 1995). The federal government had a policy of sod breaking from 1909 to the 1920s that stated the first task of the farmer is to destroy native plants in order to prepare a place for cultivated plants to grow (Potyondi 1995). Agriculture suffered during the drought years of the 1930s, and then changed as new farming methods evolved and increasingly powerful machines worked the land. Millions of hectares of prairie and aspen parkland wetlands were drained and converted to monocultures of wheat, oats, rye, barley, corn, and more recently, sugarbeets, canola, and potatoes.

Many species of grasses were introduced from Europe and Asia, including the sod-forming smooth bromegrass (Bromus inermis L.), Kentucky bluegrass (Poa pratensis L.), and timothy (Phleum pratense L.), each of which began to dominate moist sites such as along drainage systems and in the understory of wooded areas. Crested wheat grass (Agropyron cristatum (L.)) was planted extensively during the 1930s to control soil erosion, and it continues to be planted as forage for cattle because it is drought resistant, cold tolerant, and easy to seed (Gray 1996). Crested wheat grass and smooth bromegrass are now common in roadside ditches across the prairies, where they are harvested for hay.

Although agriculture increased the short-term economic output of many prairie regions, the land was not improved and populations of both vertebrates and arthropods were severely reduced or extirpated (Joern and Keeler 1995; Samson and Knopf 1996). The few remaining native grasslands now exist as fragments surrounded by agricultural fields, marginal lands, or roads. Decline of grassland landscapes has also been caused by urbanization, oil and gas development, the impoundment and extraction of water, construction of transportation corridors, and the spread of invasive species. Roads allowed other kinds of development to occur and acted as conduits for the dispersal of weeds and exotic plants (Gauthier et al. 2003). Less than 20% of native prairie remains in western Canada, including


In association with agriculture and livestock production, virtually all drainage basins have been modified. Sloughs have been drained to open up more land for farming. Water diversions have been built to form artificial ponds for water storage. All the larger rivers are dammed such that their flow patterns and rates no longer reflect natural patterns but the needs of agriculture, cities, or hydroelectricity (see Chapter 3).

How have all these human perturbations affected the prairie biota? The pace of change was so rapid, thanks to the prevailing attitude of improving the land by destroying its plant cover, that the opportunity for observation and reflection was largely missed. As Berry (1986) commented on the effects of prairie agriculture, We dont know what were doing because we dont know what we have undone. For the vast majority of prairie arthropods, the effects of this massive ecosystem disruption are unknown.

Overview of Arthropods Found on Canadas Grasslands

Insects, spiders, and mites are the most diverse and abundant animals in the native grasslands of Canada (Danks 1979). They are the most prominent herbivores and detritivores and are important in controlling the amount of living and dead organic material that accumulates and in cycling nutrients (Curry 1994; Whiles and Charlton 2006). Grasslands provide a multitude of microhabitats for arthropods. Even bare ground is vital to certain ants and beetles, as is the soil beneath, with its moisture-retentive microhabitats that are used by an array of ground-dwelling species.

Plants represent an abundant resource for insects and have served as a platform for a massive proliferation of species, resulting in some of the most complex relationships found in the natural world (Schoonhoven et al. 2006). Insects and plants have shared a long evolutionary history (Gullan and Cranston 2005) and as a result, many groups are exclusively phytophagous and speciose. Most species of grassland plants support arthropod communities of generalist and specialist herbivores, which in turn support generalist and specialist natural enemies.

Most interactions between prairie insects and plants can be grouped into one of two categories based on the impact insects have on the plants (Gullan and Cranston 2005). The first group includes those that chew or scrape leaves, sink their stylet-shaped mouthparts into the vascular bundles to suck fluids, chew on seeds, mine between the epidermal layers of leaves, chew tunnels within stems, or induce galls. Those that feed on xylem remove mostly water and amino acids and can cause water stress and reduced productivity (Meyer and Whitlow 1992). Phloem feeders remove appreciable amounts of sugars and can act as carbohydrate sinks (Inbar et al. 1995). Gall-inducing insects are found on many grassland plants (see Chapters 12 and 13), including forbs, shrubs, and trees, and influence the transport of assimilates within attacked organs (Harris and Shorthouse 1996). The second category is the pollinators, which includes many species of insects in the orders Lepidoptera, Hymenoptera, Diptera, and Coleoptera that feed on pollen or nectar and are required in the reproduction of plants.

Prairie insects that feed on grasses and other plants occupy a number of distinct niches. Ectophages feed externally on leaf tissues by chewing, scraping, or sucking. Endophages feed surrounded by plant tissues and include leaf miners, gallers, and borers. These feeding habits influence the extent to which herbivores are protected during different life stages from attack by predators, parasites, and parasitoids. Foliage-chewing insects belong primarily to the Orthoptera (especially the grasshopper family Acrididae), Lepidoptera (especially the family Noctuidae), Hymenoptera (mainly the sawflies), and Coleoptera


(mainly Chrysomelidae and Curculionidae). Sap feeders mostly belong to the Hemiptera, Thysanoptera, and Acari (mites). Stem-boring herbivores belong primarily to Hymenoptera (Cephidae, Eurytomidae), Lepidoptera (mainly Pyralidae, Noctuidae), and Coleoptera (mainly Cerambycidae, Mordellidae, Chrysomelidae).

Most grassland plants have many species of arthropods associated with them, the assemblage of which is known as a component community (Price 1997). Component communities are formed of several guilds of species that exploit the same resource in a similar manner. For example, shrubs of wild roses (Fig. 2), common in all grasslands from British Columbia across the prairies to southern Ontario, have guilds of arthropods that include many species of leaf eaters (Fig. 3), leaf miners (Fig. 4), pollinators (Fig. 5), predators of pollinators (Fig. 6), fluid suckers (Fig. 7), stem borers (Fig. 8), root chewers (Fig. 9), and suckers of root fluids (Fig. 10).

Grasses provide an abundant resource for arthropods and frequently sustain large populations (Dyer et al. 1982). Larvae of moths, butterflies, and grasshoppers commonly ingest their own body weight or more in food each day, and thus the ratio of biomass removed to grazer biomass is high (Bernays and Barbehenn 1987). At their optimum, leaves of grasses provide all the essential nutrients for insect herbivores. Young, actively growing leaf tissues have more protein than mature leaf tissues, but it falls rapidly during the growing season (Bernays and Barbehenn 1987).

Grasshoppers (Figs. 11 and 12) and Mormon crickets (Fig. 13) regularly consume 2123% of the annual available forage on rangelands (Hewitt and Onsager 1983) but sometimes consume considerably more during mass outbreaks. Biomass losses resulting from insect damage in grasslands are estimated to be 932% annually, although even large losses often go unnoticed (Tscharntke and Greiler 1995). Reduced grazing increases the species richness and abundance of phytophagous insects and their enemies (Watts et al. 1982).

Phytophagous insects can also influence the processes and functions of grassland ecosystems by altering plant populations and community dynamics. Through feeding and excretion, insects and other arthropods alter the quality and timing of litter inputs, contribute nutrients by their frass and honeydew, and alter energy budgets of damaged plants (Whiles and Charlton 2006). Insects can also influence litter quality and associated detrital cycles through premature leaf fall. This greenfall includes tissues that are removed during feeding but not ingested, leaves that are abscised prematurely in response to damage, and leaves that are clipped off by herbivores (Whiles and Charlton 2006). Numerous predacious and parasitic insects, along with predacious spiders (Fig. 6) and mites, feed on herbivorous insects. A rich assemblage of predacious ground beetles (Carabidae) (see Chapter 10) and spiders (see Chapter 11) feed on herbivorous insects.

Pollinating insects are indispensable in the reproduction of most forbs and shrubs and influence their distribution and abundance (Louda and Potvin 1995). Insects pollinate many of the plants in Asteraceae, which include coneflowers, sunflowers, and black-eyed Susans, as well as all introduced legumes of the family Leguminosae, or Fabaceae, which includes the pea, bean, and pulse families. Butterflies, such as the anise swallowtail Papilio zelicaon Lucas (Fig. 14) and the painted lady Vanessa cardui (L.) (Fig. 15), are avid flower visitors and are responsible for the cross-pollination of many prairie plants. The anise swallowtail is found in most of British Columbia except the north, in southern and central Alberta (Bird et al. 1995), and in southern Saskatchewan. Adults are usually seen in late spring and early summer hilltopping along the edges of coulees and ridges where males wait for passing females. The painted lady does not overwinter in Canada


Figs. 210. Guilds of arthropods found on wild roses in southern Alberta. Fig. 2. Field of wild roses near Pincher Creek, Alberta. Fig. 3. Redhumped caterpillar, Schizura concinna (Smith). The caterpillars of this moth in the family Notodontidae consume the entire leaves of many species of shrubs and trees, leaving only the veins. The fourth body segment is red and distinctly humped, with two prominent black tubercles, or spines. These caterpillars usually rest with the hind end elevated. Adults are an inconspicuous grayish-brown moth.

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and its populations depend on yearly recolonization by migrants from the southern United States (Bird et al. 1995).

Although above-ground arthropods are conspicuous and easily observed, a rich diversity of arthropods can be found on the surface of prairie soils and in its crevices, including carabid beetles, tiger beetles (Fig. 16), and ants, and in the soil below the surface. Tiger beetles (Acorn 2001) and carabid beetles chase after prey and consume prey on the surface of the ground. Ground or wolf spiders (Lycosidae) live in burrows or cracks in the soil and feed on the blood of captured prey. Centipedes feed on other arthropods and generally seek seclusion in the soil or under stones or in crevices.

Many species of insects feed on the roots of grassland plants. In some cases, underground herbivores are more important than those above ground because most primary production in grasslands occurs here (Blossey and Hunt-Joshi 2003). One study estimated that the below-ground standing crop consumed by insects is 210 times greater than the above-ground mass (Stanton 1988). The larvae and nymphs of many species of mites, scarab beetles, click beetles, and noctuid moths, along with xylem-feeding aphids and cicadas, feed on root tissues (Gullan and Cranston 2005; Nardi 2007). Ants build their tunnels below the surface, with each ant colony effectively functioning as a superorganism (Hlldobler and Wilson 1994). Large, conical anthills 1520 cm high and made of dried pieces of plants by thatching ants, Formica obscuripes Forel, are prominent features over much of the prairies. In the dry southern areas, the western harvester ant (Pogonomyrmex occidentalis (Cresson)) makes conspicuous conical nests of fine pebbles within a large bare circular area. Formica obscuripes feeds mostly on insects and the honeydew of aphids, whereas P. occidentalis feeds on seeds of grasses and forbs, which are stored in the mounds (Wheeler and Wheeler 1963).

Fig. 4. Leaf mine caused by tunnelling larva of a fly of the family Agromyzidae. Larvae feeding between the epidermal layers of the leaflets make serpentine mines that increase in width as the larva grows. Larvae then exit the leaves and drop to the ground, where they pupate and overwinter. Fig. 5. Long-horned beetle, likely Gnathacmaeops pratensis Laicharting of the family Cerambycidae, feeding on pollen. All members of this large family are phytophagous and the adults of many species feed on pollen. Larvae of most species are wood boring and prefer weakened or dying trees. Fig. 6. Crab spider, Misumena vatia (Clerck), of the family Thomisidae, sitting in a flower sucking the blood of a bee it has captured and paralyzed. Crab spiders are commonly called flower spiders because they are found on flowers lying in ambush for prey. Crab spiders change the colour of their bodies depending on the substrate on which they are hiding in order to camouflage themselves. Prey is captured with the front legs, which are longer than the others and are held out to the side, giving them a crab-like appearance. Fig. 7. Nymph of a spittle bug, Philaenus spumarius (L.). Nymphs of spittle bugs avoid desiccation by surrounding themselves with a frothy mass of bubbles made from fluids voided from the anus, along with a mucilaginous substance secreted by epidermal glands on the abdomen. Adults, which are about 8 mm in length, are called froghoppers because they look like tiny frogs. Fig. 8. Larva (arrow) of the rose stem girdler, Agrilus aurichalceus, feeding in tunnels it has excavated in the cambium beneath the bark of a stem. Girdling by the larva severs vascular bundles, preventing water from passing beyond the feeding site, and the branch dies. The adults are small (6 mm) golden to bronze-coloured metallic beetles that find new shoots in May and June and oviposit just under the bark. The larvae hatch and begin burrowing under the bark, spiralling outward from the oviposition site. Infested stems begin to wilt by late July and then die by August or September. Fig. 9. Larva of a June beetle, Phyllophaga sp., feeding on roots. Adults are robust beetles about 1520 mm in length and are dull brown. Adults fly in the evening and often turn up at lights from mid-May to early July. Identification of four species found on the prairies requires examination of genitalia. Fig. 10. Nymph of a cicada, Okanagana sp., feeding on fluids of roots. Cicadas are found throughout the grasslands wherever there are woodlands or thick brush. They spend most of their lives underground as larvae and take from 4 to 9 years to mature. Adults appear from late May to late July. Photo credits: D.J. Larson (Fig. 8); J.D. Shorthouse (all other figures).


Fig. 11. Mating pair of Melanoplus bivittatus, commonly known as the two-striped grasshopper, is a spur-throated grasshopper of the family Acrididae and subfamily Melanoplinae. This subfamily is the most diverse grasshopper group, with hundreds of species adapted to living in all grassland ecoregions. M. bivittatus is found in all the grasslands of Canada from southern British Columbia across the prairies to southern Ontario. Farming activities have transformed this species to a damaging pest of cereal crops, forages, and oilseed crops. Photo by D.J. Larson.

Many species of insects and mites are detritivores and scavengers. They play a key role in detrital pathways within the soils, where they reduce the particle size of decaying leaf litter, wood, carrion, and dung through comminution (breakdown of organic matter into smaller particles; Gullan and Cranston 2005). The Acari, which include herbivores, fungivores, detritivores, and predators, are abundant and diverse in prairie soils (see Chapter 7). As detritivores, they hasten the decomposition of dead organisms, resulting in a quick return of carbon and mineral nutrients to the soil, where they become available to plants. Some insects are phytophagous in the adult stage and predacious in the immature stages. Adults of blister beetles, such as Nuttalls blister beetle (Lytta nuttali Say) (Fig. 17), feed on flowers and leaves of various plants, whereas their larvae are predators on the eggs of grasshoppers or parasitoids in the nests of solitary bees. Other insects such as ladybird beetles feed on phytophagous insects in both the immature and adult stages (Acorn 2007).

Grassland ungulates produce vast amounts of fibrous and nitrogen-rich dung that is fed upon by many species of coprophages (dung-feeding organisms), with the overwhelming majority being beetles and flies. Certain families are rich in dung feeders, namely, the Scarabaeidae in the Coleoptera (Floate and Gill 1998) and the Muscidae, Calliphoridae, Sarcophagidae, Sepsidae, and Sphaeroceridae in the Diptera (Gullan and Cranston 2005). The role of dung and carrion insects is important in nutrient cycling. Dung and carrion are prime examples of patchily distributed and ephemeral resources and are a food source for distinct communities of insects that change in numbers and species during aging and decomposition (Hanski and Cambefort 1991). Dung was, and still is, more common in


grasslands than in any other habitat in Canada. Of interest, most of the surface dung in Canada today is fed upon by introduced species of beetles, whereas the endemic fauna of dung beetles feed mainly on subterranean rodent dung (Gordon and Skelley 2007).

Of the many insects inhabiting Canada, perhaps the most exemplary of those adapted to prairie conditions are leafhoppers tolerant to environmental change (see Chapter 8). Grass feeding in this group appears to have favoured speciation more than in any other (Ross 1970). Grassland arthropods are highly susceptible to changes in the environment, with climate being the dominant force determining their distribution and abundance. They must be able to tolerate a combination of cold winter temperatures, a short summer growing season with temperatures frequently exceeding 30 C, scarcity of surface water, infrequent rains during the summer, and the desiccating effects of strong winds. Most species of grassland insects have wings, and, like the immatures of spiders, use the wind to disperse (den Boer 1990). However, many species of soil- and soil-surface-dwelling insects are flightless, such as Mormon crickets (Anabrus simplex Haldeman) (Fig. 13) and various species of seed bugs (Lygaeoidea) and ground beetles.

Most grassland arthropods become dormant over the winter and enter into diapause, an important mechanism that allows them to cope with harsh winter conditions (Tauber et al. 1986; Danks 2002). Insects that overwinter above the snow have evolved the ability to tolerate temperatures from 20 to 35 C by becoming either freezing intolerant or freezing tolerant (Lee 1991). Those overwintering below the ground surface experience

Fig. 12. Adult Camnula pellucida, commonly known as the clear-winged grasshopper, is a band-winged grasshopper of the family Acrididae and subfamily Oedipodinae. Large lobed hind wings, usually with spots and bands, distinguish band-winged grasshoppers from other species. C. pellucida is found in all the grasslands of Canada from southern British Columbia across the prairies to southern Ontario. These grasshoppers feed mainly on grasses and can become severe pests of cereals. When populations are high, they hatch in egg beds that may contain as many as 3,000100,000 eggs per square foot. Young nymphs walk away from egg beds to green vegetation and older individuals march in cohesive bands. Adults often swarm and fly several hundred metres on hot, sunny days. Photo by D.J. Larson.


periodic freezing because frost commonly penetrates 13 m into the ground, depending on the depth of the snowpack.

We know a great deal about the fluctuations in populations of some species of prairie insect pests that have been tracked, analyzed, modelled, and predicted by regional entomologists. A suite of native species has thrived in agroecosystems, including the migratory grasshopper (Melanoplus sanguinipes (F.)), pale western cutworm (Agrotis orthogonia Morrison), wheat stem sawfly (Cephus cinctus Norton), prairie grain wireworm (Ctenicera aeripennis (Kirby)), and green stink bug (Chlorochroa uhleri (Stl)) (Riegert 1980).

Grasshoppers are synonymous with grasslands and historically have been important herbivores on the prairies. They have been well-known to humans from the earliest inhabitants to modern farmers (Riegert 1980). Grasshoppers are paurometabolous; that is, they develop by gradual metamorphosis whereby the immature stages (nymphs) resemble small adults and typically have wing buds. Nymphs live in the same habitat as adults and feed on the same plants. Nymphs are easy to observe and enumerate, given their body size and high activity, and as a result, much is known about their biology (e.g., Otte 1981; Vickery and Kevan 1985; Chapman and Joern 1990; Johnson 2001, 2002, 2003). Most species of grasshoppers are not highly specialized herbivores. Hence, their population dynamics are not driven by changes in the availability of a few species of plants. The populations of most species are highly variable, which reflects factors of weather, fire, grazing, and differences in land use (Gage and Mukerji 1977; Joern 2005; Powell et al. 2007). The frequency of

Fig. 13. The adult female Mormon cricket, Anabrus simplex Haldeman, is a ground-dwelling katydid of the family Tettigoniidae and is not a true cricket. Mormon crickets live in rangeland dominated by sagebrush and forbs. They are large insects and can feed on more than 400 species of plants. They prefer forbs but also eat grasses, sagebrush, and other insects. They feed voraciously on wheat, barley, alfalfa, sweet clover, truck crops, and garden vegetables. Despite its flightless state, the Mormon cricket is a mobile insect. The first four instars move about extensively in search of food and shelter and in short migration, but adults can migrate about 0.5 km a day and can travel 80 km in their lifetime. Photo by D.J. Larson.


Fig. 14. Anise swallowtail, Papilio zelicaon Lucas. Larvae feed on various members of Umbelliferae. Adults are usually seen in late spring and early summer hilltopping along edges of coulees and ridges. Photo by D.J. Larson.

fires and extent of grazing by herbivores such as bison once altered the characteristics of habitats that were beneficial to grasshoppers (Vinton et al. 1993; Hartnett et al. 1996).

There are 155 species of short-horned grasshoppers (Orthoptera sensu) (Vickery and Kevan 1985) in Canada, with approximately half of these (83 species) occurring on the prairies. A number of these species have been of economic importance (Beirne 1972), but only four species are regularly serious pests: the migratory grasshopper Melanoplus sanguinipes, the Packard grasshopper M. packardii Scudder, the two-striped grasshopper M. bivittatus (Say) (Fig. 11), and the clear-winged grasshopper Camnula pellucida (Scudder) (Fig. 12). Each of these species exemplifies how well grasshoppers are adapted to prairie conditions. Under ideal food and weather conditions, they multiply quickly and when present in large numbers, they consume much of the local vegetation, whether crop or pasture. An adult grasshopper can eat 30100 mg (dry weight) of plant matter each day and, with densities from 300 adults and 1,000 nymphs per square metre being recorded for C. pellucida (Beirne 1972), infested areas can be quickly denuded.

Populations of prairie grasshoppers are largely controlled by the weather (Beirne 1972). Drought is beneficial to grasshoppers, with positive correlations in population size occurring in drought years and in periods of hot, dry weather from July to September (see references in Joern and Gaines 1990), whereas populations tend to collapse in cool, wet weather. Warm, humid weather promotes the infection and spread of fungal diseases. Birds and various mammals eat nymphal and adult grasshoppers and various small mammals consume the eggs. A diverse community of insects, including various species of bee flies (Bombyliidae) and blister beetles (Meloidae) (Fig. 17), are egg predators or parasites. However, the role of these natural enemies in controlling grasshopper populations is probably limited.


Most grasshoppers are winged as adults, but their dispersal abilities vary. They are likely local in their movements but some, such as C. pellucida and M. sanguinipes, are good fliers and can spread rapidly during an outbreak. Marching swarms or bands of nymphs of C. pellucida often occur in outbreak areas. The most famous migratory grasshopper of the prairies is the now extinct Rocky Mountain grasshopper (Melanoplus spretus (Walsh)). During the 1800s, this species was an intermittently serious pest, but it has not been seen since the last specimens were collected in Manitoba in 1902 (see Vickery and Kevan 1985 for a good historical review). Lockwood (2004) showed how human disruption of mountain valleys frequented by M. spretus when their populations were low was a key factor responsible for the extinction of this species.

Some recently introduced insects that do not feed on crops are changing the face of the prairies. For example, the rose stem girdler, Agrilus aurichalceus Redtenbacher (Fig. 8), a buprestid beetle, was originally introduced into North America in New Jersey, but has spread to the prairies, where it was first recorded in 2003 (Larson 2003). Its effect on roses, especially Rosa woodsii Lindl., has been devastating. Rose patches that once formed almost impenetrable stands in moist soils of draws and coulee bottoms have been reduced to open patches of scattered, small-stemmed shrubs. Few stems remain that are older than two years, as stems of this size are killed by the girdler. Another example is the introduced weevil, Cryptorhynchus lapathi (L.) (McNamara 1991), with larvae that bore into the stems of willows such as sandbar willow (Salix interior Rowlee), killing the whole above-ground part of the plant. Stream banks, coulees, moist depressions, and pond edges typically supported stands of willows, which in turn supported a diverse insect fauna, but ravines full of dead or moribund willow are now common. In a landscape with few prominent woody plants, the loss or reduction of the few dominant species is a major blow to the landscape.

Fig. 15. Painted lady, Vanessa cardui (L.). This butterfly does not overwinter in Canada, with its populations depending on yearly recolonization by migrants from the southwestern United States. In some years, this species is absent, whereas in other years, it is dominant and its larvae defoliates most thistles. Photo by D.J. Larson.


Major changes in the insect fauna are a regular feature on the prairies. For example, the dominant butterflies over the three-year period of 20052007 were as follows:

1. 2005: Painted lady arriving in June and July and perishing in the fall (Gollop and Leighton 2005)

2. 2006: Cabbage butterfly (Pieris rapae (L.)) in huge numbers, appearing to originate in the prairie/parkland area (Gollop and Leighton 2007a)

3. 2007: Monarch butterflies (Danaus plexippus (L.)), not in the huge numbers of the two previous species, but instead of its usual uncommon-to-rare status, it was a major species in butterfly counts (Gollop and Leighton 2007b)

Conclusions

Grasslands are structurally simple terrestrial environments whose arthropod inhabitants are easily observed compared with their relatives in forest canopies. Among the most intensively studied arthropods in Canada are those considered pests of agroecosystems, where some species consume a significant proportion of our cereal and oilseed crops. However, there are hundreds of non-pest species associated with remnant and altered grassland ecosystems in Canada, along with those altered for agriculture, that warrant attention (Tscharntke and Greiler 1995; Whiles and Charlton 2006). Studies on these latter

Fig. 16. Big sand tiger beetle, Cicindela formosa, of the family Carabidae, subfamily Cicindelinae, is a common ground dweller in dry upland areas, blowouts, and edges of sand dunes in grasslands from British Columbia to southern Ontario. Like all tiger beetles, they have long legs, run and fly fast, and have large mandibles for capturing prey. Larvae are also predacious and live in vertical burrows in the soil. They prop themselves at the entrance to their burrows and wait with jaws wide apart to capture passing insects. Photo by D.J. Larson.


species are more urgent, given that most of the grass-dominated ecosystems in Canada, as in other temperate parts of the world, have been largely converted to agroecosystems (Sala et al. 1996; Anderson 2006).

Much of the native grassland has been fragmented or eliminated, with corresponding decreases in native plant and animal life. As public concern grows over the loss of biodiversity, the scientific community is under pressure to understand and preserve the grassland fragments that remain. At the same time, international obligations dictate that Canada catalogue, monitor, and protect the flora and fauna found within its borders. Thus, there is an urgent need to survey and assess the biodiversity of the remaining grassland arthropods, the majority of which undoubtedly play important but as yet largely undocumented roles in the ecosystems. Adding to the urgency is that perhaps half of the North American species of grassland arthropods await description (Samson and Knopf 1996).

The grasslands of Canada are fascinating in their own right, but much more knowledge of their biota is needed, in particular the arthropod fauna. The information about arthropods reported in this book just scratches the surface of the knowledge base required by society. All the authors who have penned these chapters call for both private and government sectors to fund new research projects that will not only improve our understanding of the composition and function of remaining grassland biota, but will also provide the means by which our natural and semi-natural grasslands and agroecosystems are sustained into the future.

Fig. 17. Nuttalls blister beetle, Lytta nuttali, of the family Meloidea, shown on silver lupine, is one of the largest and most conspicuous blister beetles on the prairies. Blister beetles get their name from a toxin called cantharidin found in their body fluids. Hemolymph (blood) containing this toxin is exuded from the leg joints when they are disturbed. The toxin protects the beetles from being eaten by birds and certain predaceous insects and causes blisters on contact with human skin. The larvae are predacious on grasshopper eggs and the adults feed on plant foliage and flowers. They can become pests of alfalfa, corn, beans, and ornamentals when grown next to rangeland. Photo by D.J. Larson.


Acknowledgements

We thank Lo Larivire of the Department of Geography at Laurentian University for drawing the map showing grasslands of Canada and Geoff Scudder for his suggestions on improving the text.

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