Trembling aspen, Populus tremuloides Michx. (Salicaceae), is the most widely distributed tree species in North America (Perala 1990) and is considered to be an ecologically (Hogg et al. 2002) and economically important (Brandt et al. 2003) component of the boreal forest. Due to the recently increased economic value of trembling aspen (Brandt et al. 2003), the impact of native insect defoliators on tree growth and mortality has become commercially important. Two of the most significant defoliators of trembling aspen throughout its range in Canada are the forest tent caterpillar (FTC), Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), and the large aspen tortrix (LAT), Choristoneura conflictana Walker (Lepidoptera: Tortricidae).

The wheat stem sawfly, Cephus cinctus Norton, is a major insect pest in dryland wheat (Triticum L. spp.; Poaceae) fields in the northern Great Plains of the United States and in southern regions of the prairie provinces of Canada. Field infestations by this pest commonly show a distinct “edge effect”, with infestation levels highest at the field edge and declining inwards. In this study, we characterized the edge effect of C. cinctus infested wheat fields in Montana at four locations in two separate years. "Infestation level" refers to the average proportion of wheat stems infested with C. cinctus in samples collected in a given wheat field. The gradual decrease in C. cinctus infestation towards the centre of wheat fields is referred to as the “infestation slope”, and it was presented as a proportion of infestation level at field edges. We showed that (i) for most of the fields bordering grassland or fallow wheat, a simple exponential decline curve provided a significant fit to the infestation slope; (ii) the infestation slopes in different fields and in different directions within fields were similar and appeared to be independent of the overall infestation level; and (iii) the relationship between infestation level and the proportion of samples infested followed an asymptotic curve, which indicates a high level of dispersal of ovipositing C. cinctus females. The general perception has been that the edge effect of C. cinctus infestation is a result of ovipositing C. cinctus females being both weak flyers and short-lived, but our results do not fully corroborate this perception. Currently, the only reliable way to detect C. cinctus infestations is to dissect individual stems and look for developing instars. However, this type of sampling is extremely time consuming and labor intensive and therefore impractical for wheat growers. Increasing the understanding of the spatial patterns in C. cinctus infestations is a first step towards development of an optimal sampling plan for this important field pest. Thus, the results presented are relevant for researchers involved in sampling designs and integrated pest management procedures for field pests. We discuss behavioral and evolutionary factors that may contribute to the edge effect of C. cinctus infestations.

The host-colonization behavior of the red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), was investigated in stands of ponderosa pine, Pinus ponderosa P. & C. Lawson (Pinaceae), with black stain root disease in the central Sierra Nevada of California. By felling live trees, we found that trees with pitch tubes produced during the initiation of tunneling by D. valens had a significantly higher incidence of black stain root disease, caused by Leptographium wageneri var. ponderosum (Harrington et Cobb), than trees without pitch tubes. Trees with the most D. valens pitch tubes had the greatest likelihood of being diseased. Additionally, observations over a 3-year period revealed that trees with D. valens pitch tubes had a significantly higher mortality rate than trees without pitch tubes. Infection by L. wageneri was confirmed for most of the trees that died, and death typically did not occur without mass attacks by the western pine beetle, D. brevicomis LeConte, and (or) the mountain pine beetle, D. ponderosae Hopkins. Trees with the most D. valens pitch tubes had the highest mortality rate. An experiment was conducted to compare the attraction of D. valens and other insects to wounded-diseased, wounded-symptomless, and unwounded trees. More D. valens, Spondylis upiformis Mannerheim (Coleoptera: Cerambycidae), and Hylastes spp. (Coleoptera: Scolytidae) were attracted to wounded trees than to unwounded trees. Catches of these beetles on wounded-diseased trees were not significantly different from catches on wounded-symptomless trees.

For over three decades, the importance of taxon sampling curves for comparative biodiversity studies has been repeatedly stated. However, many entomologists (both within Canada and worldwide) continue to publish studies without standardizing their data to take sampling effort into account. We present a case study to illustrate the importance of such standardization, using the collection of spiders (Araneae) by pitfall traps as model data. Data were analyzed using rarefaction to represent one example of a taxon sampling curve, and by a variety of traditional diversity indices to describe alpha diversity. Raw species richness and single-index diversity measures (Shannon–Wiener, Simpson's, and Fisher's α) provided contradictory results. Rarefied species richness standardized to the number of individuals collected enabled more accurate comparisons of diversity and revealed when sampling was insufficient. Focusing on arthropods occurring in forested ecosystems, we also examined the use of taxon sampling curves in current literature by reviewing 133 published articles from 14 journals. Only 26% of the published articles in our review used a taxon sampling curve, and raw species richness and the Shannon–Wiener index of diversity were the most commonly used estimates. There is clearly a need to modify how alpha diversity is measured and compared for arthropod biodiversity studies. We recommend the abandonment of both raw species richness and single-index measures of diversity, and reiterate the need to use rarefaction or a related technique that allows for meaningful comparisons of species richness while taking into account sampling effort.

Traps baited with either ethyl (E,Z)-2,4-decadienoate (pear ester) or (E,E)- 8,10- dodecadien-1-ol (codlemone) (Pherocon® CM-DA™ and Megalure CM™ lures, respectively) were used to develop action thresholds for codling moth (Cydia pomonella (L.)) in apple (Malus domestica Borkh.; Rosaceae) orchards treated with sex pheromones for control of this pest. Studies were conducted in 102 orchards treated with 500–1000 ISOMATE®-C PLUS dispensers per hectare during 2000–2002. Pairs of traps were placed within two 1.0-ha plots within each orchard. Fruit injury was assessed at mid-season and prior to harvest in each plot. The numbers of female and total moths caught in pear ester-baited traps and male moths caught in codlemone-baited traps were used to develop action thresholds. Thresholds were based on the minimum cumulative number of moths per trap in ≥95% of traps in unsprayed plots with no fruit injury. Specific thresholds were established for the first insecticide spray targeting the start of egg hatch and for the first and second moth flights. The proportion of plots with mid-season fruit injury that had cumulative moth catches below the action threshold at first spray and at second moth flight was determined using the established action threshold and thresholds reduced incrementally to ≥1 moth per trap. Moth catches below the threshold at first spray were less common in plots with high levels of fruit injury (>0.3%) than in plots with low levels of fruit injury and more common with codlemone-baited traps than with pear ester-baited traps. An action threshold of ≥1 moth in a pear ester-baited trap at first spray eliminated the error in predicting fruit injury in plots at mid-season. Conversely, a high proportion of traps baited with either lure failed to predict low levels of fruit injury at harvest in unsprayed plots regardless of the cumulative moth threshold used during the second moth flight.

The alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), can severely damage the first cutting of alfalfa, Medicago sativa L. (Fabaceae), in much of Iran. The pest has been parasitized by several parasitoids including Oomyzus incertus (Ratzeburg) (Hymenoptera: Eulophidae), a gregarious larval endoparasitoid. This wasp can parasitize up to 30% of weevil larvae in alfalfa fields in northern Iran. It produces three to four generations per year, and the female prefers the fourth instar of the host for oviposition. Each female lays 2 to 22 eggs per host, which hatch within 47–60 h. The life cycle is completed in about 2 weeks, upon pupation inside the host. This species is predominantly present during the summer months in alfalfa fields (Streams and Fuester 1967).

The Holarctic genus Chrysoclista (Lepidoptera: Agonexenidae) consists of very distinctive, small, brightly coloured moths whose larvae bore in the bark of deciduous trees. There are seven species worldwide including three found in Europe, two found in the Caucasus, and two Nearctic species, C. cambiella (Busck, 1915) and C. villela (Busck, 1904). In addition, the Palearctic species C. linneella (Clerck, 1759) has been introduced to North America (Karsholt 1997).

In Europe, C. linneella is found across most of the continent, in all of the Baltic and Fennoscandian countries, Great Britain, the Netherlands, Belgium, Luxembourg, Germany, Poland, Czech Republic, Slovakia, Hungary, Austria, Switzerland, France, Spain, Italy, Rumania, Russia (Karsholt and Razowski 1996), Turkey, and Ukraine (S. Koster, personal communication).

Urbanization causes the fragmentation of natural habitats into isolated patches surrounded by anthropogenic habitats. Fragment size and the intensity of human disturbance have been shown to affect both composition and diversity of arthropod communities, but most groups have been understudied. We investigated effects of urbanization on ant assemblages (Hymenoptera: Formicidae) in and around the Molson Reserve, a preserved maple-beech forest surrounded by residential properties near Montréal, Quebec. We studied how local ant assemblages differed in terms of composition, abundance, and species richness, depending on whether they were situated in the interior forest, in adjacent residential backyards, or at the edge between these two habitats. We also compared an intact forest interior with a younger and moderately disturbed forest (“buffer zone”) between the urban matrix and the interior forest. Few differences were detected between the buffer zone and the intact forest interior. Extrapolated estimates of species richness suggest that it is lowest in the forest interior and highest in urban zones. Community composition, as investigated with ordination analysis, revealed a clear difference between the fauna of urban sites and the fauna of edges and forest interiors, and analyzing the relative abundance of ants showed residential backyards to contain the most ants. Urban assemblages were characterized by several competitively dominant species, including one introduced or “tramp” species. The occurrence of aggressive and dominant species in urban sites and at the edges of the Molson Reserve could potentially interfere with the dispersal and immigration of ground-dwelling arthropods and negatively affect local diversity or community composition in isolated forest reserves in urban centres.

The western conifer seed bug, Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae), is a polyphagous pest of coniferous trees (Hedlin et al. 1981). Native to western North America, the seed bug has expanded its range to include eastern Canada and the United States (McPherson et al. 1990; Gall 1992; Marshall 1992; Ridge-O'Connor 2001; Bates 2002) and was recently introduced into Europe (Taylor et al. 2001). Both adults and nymphs feed by inserting their stylets into cones and digesting the contents of developing seeds, and they can cause serious economic losses in high-value seed orchards (Strong et al. 2001; Bates et al. 2002; Bates and Borden 2005).

The invasive wood-boring beetle Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) poses a serious threat to deciduous trees in North America and Europe, where it has been introduced in solid wood packing material from China (Haack et al. 1997; Krehan 2003). This beetle attacks and ultimately kills a wide variety of hardwood tree species (Nowak et al. 2001; Lingafelter and Hoebeke 2002); it has infested urban shade trees in Canada (Canadian Food Inspection Agency 2004), the United States (Haack 2003), and Austria (Tomiczek 2003) and has damaged poplar (Populus L.; Salicaceae) plantations in its native China (Luo et al. 2003).

The red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Scolytidae), is a common bark beetle species found throughout much of North America. In California, D. valens and the California fivespined ips, Ips paraconfusus Lanier (Coleoptera: Scolytidae), are sympatric and often colonize the same tree. In an unrelated study, we observed that I. paraconfusus attack densities in logging debris were inversely related to D. valens attacks on freshly cut stumps. In this study, we test the hypothesis that allomonal inhibition occurs between these two species. Components of the aggregation pheromone of I. paraconfusus (racemic ipsenol, (+)-ipsdienol, and (–)-cis-verbenol) inhibited the response of D. valens to attractant-baited traps. Substitution of racemic ipsdienol for (+)-ipsdienol did not alter this effect. Doubling the release rate did not enhance inhibition. Racemic ipsdienol was not attractive to I. paraconfusus. Temnochila chlorodia (Mannerheim, 1843) (Coleoptera: Trogositidae), a common bark beetle predator, was attracted to the I. paraconfusus aggregation pheromone. These results could have important implications for the development of an effective semiochemical-based management tool for D. valens.

The hemlock woolly adelgid (HWA), Adelges tsugae Annand, is the number one threat to hemlock (genus Tsuga Carr.; Pinaceae) forests in eastern North America. Sasajiscymnus tsugae (Sasaji et McClure), an introduced coccinellid from Japan, is a promising biological control agent for HWA. In mass rearing of S. tsugae, the main goals are to maximize adult beetle production, reduce the amount of human labor, and minimize production costs. Significantly higher adult S. tsugae production and survivorship from egg to adult were observed in a modified rearing box compared with a conventional rearing box. The 30 modified boxes produced 4400 more beetles than the 30 conventional boxes. Over time, egg to adult survivorship decreased because of larval cannibalism at densities above 1650 larvae per rearing box. Additionally, warmer weather conditions increased the number of insect and spider predators incidentally introduced via HWA-infested hemlock twigs. There was no significant difference in the time required to prepare modified and conventional boxes for initial introduction of eggs, but significantly less time was required to add water, honey, and HWA-infested twigs to the modified boxes. The additional cost and time required to add modifications to each box was compensated for by the increased number of adult S. tsugae produced and the time saved during the 35 days of scheduled maintenance as eggs hatched and larvae developed to adults.

Corn rootworms, Diabrotica Chevrolat spp. (Coleoptera: Chrysomelidae), are major pests of corn, Zea mays L. (Poaceae), in North America. Overwintering eggs hatch in the spring, and larvae feed on the root system, where they complete development. Emergent adults feed on vegetative and reproductive aerial structures of corn and oviposit in soil cracks or at the base of plants. Although feeding on silks by adult corn rootworms reduces the yield of corn, most of the damage results from root injury caused by larval feeding (Levine and Oloumi-Sadeghi 1991).

The wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is an insect pest in dryland wheat cropping systems in the southern Canadian Prairies and the northern Great Plains of the United States (Morrill 1997). Yield losses caused by C. cinctus are due to reduced head weight (Holmes 1977; Morrill et al. 1992) and lodging, which decreases harvest efficiency. Estimates of yield losses in Montana alone are about US$25 million per year.

The wheat midge, Sitodiplosis mosellana (Géhin), is an infrequent but devastating pest that has been present in western North America for at least 100 years. This note provides the first published report of the presence of the wheat midge and its parasitoid, Macroglenes penetrans (Kirby), in Montana. Annual surveys were conducted in Daniels, Roosevelt, Sheridan, and Valley counties of northeastern Montana for 5 years (2000–2004) using a systematic soil sampling method to collect overwintering wheat midge larvae. In addition, in 2004, infested wheat heads were collected from 10 fields in Sheridan County, and wheat midges and parasitoids were reared. The wheat midge occurred in all four counties, though at relatively low levels. Densities fluctuated across years and locations, with the highest densities (>200 midge larvae/m2) occurring in Sheridan and Roosevelt counties. Macroglenes penetrans was found at all 10 sample sites and constituted up to 52% of the emerged adults (midges + parasitoids).

Because the detectability of host eggs is low, egg parasitoids rely on infochemicals other than those from the host egg itself, such as host plant synomones (Nordlund 1994; Meiners et al. 2000) and adult host kairomones (Nordlund et al. 1983; Nordlund 1994; Colazza et al. 1999; Meiners et al. 2000). Egg kairomones are used only in the final stages of host selection (Kainoh et al. 1982; Strand and Vinson 1982, 1983; Nordlund et al. 1987; Meiners et al. 2000; Takasu and Nordlund 2001).

Pitfall traps containing a preservative have become the standard method of sampling for epigeal invertebrates such as carabid beetles and cursorial spiders. However, they often result in high levels of mortality for small mammals and amphibians. We compared the carabid, spider, and vertebrate captures within five pitfall trap types (conventional trap, funnel trap, shallow trap, Nordlander trap, and the ramp trap) to determine the trap type that would reduce vertebrate incidental catch without compromising the capture of invertebrates. We also examined the effect of a mesh screen over pitfall traps on carabid beetle and vertebrate catches. All modifications to the conventional trap design resulted in a reduction in both small mammal and amphibian captures. The shallow pitfall trap and the funnel trap captured a carabid beetle and spider fauna similar to that captured by the conventional trap. The species compositions of the ramp trap and the Nordlander trap were different from those of the other trap types, but these traps were more efficient, capturing more species per individual captured. The ramp trap appeared to be the method of choice for sampling epigeal spiders. Thus, the choice among trap designs for invertebrates depends on the objectives of the study. However, an alternative to the conventional trap design should always be considered to reduce small mammal mortality.

Pitfall traps provide an easy and inexpensive way to sample ground-dwelling arthropods (Spence and Niemela 1994; Spence et al. 1997; Abildsnes and Tommeras 2000) and have been used exclusively in many studies of the abundance and diversity of ground beetles (Coleoptera: Carabidae). Despite the popularity of this trapping technique, pitfall traps have many disadvantages. For example, they often fail to collect both small (Spence and Niemela 1994) and “trap-shy” species (Benest 1989), eventually deplete the local carabid population (Digweed et al. 1995), require a species to be ground-dwelling in order to be captured (Liebherr and Mahar 1979), and produce different results depending on trap diameter and material, type of preservative used, and trap placement (Greenslade 1964; Luff 1975; Work et al. 2002).