Pissodes terminalis Hopping attacks the current year's leader growth of lodgepole pine, Pinus contorta var. latifolia Engelmann (Pinaceae), causing its death or defects such as crooks, forks, and multiple leaders (Maher 1982). In southern British Columbia, the duration of the growing season can vary greatly among ecosystems as evidenced by the presence of several biogeoclimatic zones and subzones (Lloyd et al. 1990). In most of these zones, P. terminalis overwinters as fourth instar larva and adult emergence occurs the following season, thus requiring more than 1 year to complete its life cycle. However, in warmer ecosystems and in some silviculturally manipulated stands, its life cycle can be univoltine (Maclauchlan 1992; Cameron and Stark 1989). Knowledge of laboratory temperature requirements for P. terminalis development would enable future comparisons with field temperature accumulations and insect development.

A larval population of spruce budworm, Choristoneura fumiferana (Clemens), was monitored for 5 d following aerial application of a commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki to investigate dose acquisition and expression (larval mortality, recovery, feeding, and growth) in relation to spray deposition and persistence of spray deposits. The main objective was to test if previous laboratory observations on how B. thuringiensis affects feeding and dose ingestion by spruce budworm larvae hold true under field conditions. About 40% of the treated population ingested a lethal dose within 1 d after spray application. Lethally dosed larvae died without further feeding upon transfer from treated foliage to (untreated) artificial diet. Resumption of feeding by larvae that survived the treatment was delayed relative to larvae from the control population during 3 d following spray application; during that time, normal feeding activity and larval weight gain were suppressed. Inhibited feeding by survivors appeared to prevent further dose uptake because the proportion of lethally dosed larvae in daily collections did not increase despite significant residual spray deposits in budworm feeding sites. Restoration of "normal" recovery times by the fourth day coincided with a 65–85% reduction in persistence of the pathogen on the foliage and did not result in further lethal dose acquisition, as treatment-induced mortality dropped to about 20% on the 4th and 5th days. The observations are consistent with previous laboratory observations of how B. thuringiensis affects larval feeding and with the hypothesis that feeding inhibition may be a limiting factor in the acquisition of a lethal dose.

A survey of nine populations of the European earwig, Forficula auricularia L., species complex from eastern North America revealed the presence of the two sibling species recently identified as species A and B. A mitochondrial analysis, based on restriction polymorphism observed on the 16S rRNA and the cytochrome oxydase regions, proved to be a rapid method to identify and distinguish these two species. Furthermore, consistency between these mitochondrial data and a biological diagnosis, based on the dates and number of oviposition periods in each population, revealed that species A and B occupy different habitats. These observations are consistent with the hypothesis of multiple introductions of the two species on the Atlantic coast of North America, followed by a selection of the most adapted species to each habitat.

Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae) multiple nucleopolyhedrovirus (CfMNPV) expressing green fluorescent protein was used to study aspects of nucleopolyhedrovirus infection in the spruce budworm. The temporal and spatial distribution of fluorescence indicated that the virus infected the midgut, entered the tracheal system, and traveled to the epidermis, fat body, and muscles. In contrast to Autographa californica (Speyer) (Lepidoptera: Noctuidae) multiple nucleopolyhedrovirus (AcMNPV) infection, hemocytes from infected C. fumiferana did not exhibit fluorescence until after CfMNPV had passed from the midgut into the tracheae. Therefore the role of hemocytes may be limited during CfMNPV infection. Also the fluorescence pattern spread from the tracheolar cells to tracheal epithelial cells throughout the tracheal system. Our results indicate that the temporal and spatial events involved in CfMNPV infection of C. fumiferana larvae are consistent with those observed in other lepidopteran hosts infected with AcMNPV Minor deviations between these two systems may be attributed to differences in virulence, infection rate, and possibly host range of the virus.

The female-produced sex pheromone blend of the pandora moth, Coloradia pandora pandora Blake, a pest responsible for periodic defoliation of pine forests in the western United States, has been identified. The pheromone consisted of a mixture of E10,Z12-hexadecadienal, E10,Z12-hexadecadienyl acetate, and E10,E12-hexadecadienyl acetate. All three components were essential for optimal attraction. E10,Z12-Hexadecadienol, tentatively identified in trace amounts in pheromone gland extracts, elicited strong responses from male antennae in coupled gas chromatography – electroantennogram analyses but had no apparent effect as a pheromone component at physiologically relevant levels. Hexadecanal, octadecanal, and hexadecyl acetate also were identified in extracts of female pheromone glands but elicited no responses from male antennae, nor did they appear to be components of the attractant blend. In field trials, each trap baited with the optimized three-component blend of E10,Z12-hexadecadienal, E10,Z12-hexadecadienyl acetate, and E10,E12-hexadecadienyl acetate captured an average of more than 40 male moths per night.

Esterase banding patterns in native polyacrylamide gel electrophoresis, squash silver leaf (SSL) induction, and tomato yellow leaf curl begomovirus-Sardinia (TYLCV-Sar) transmission capability were investigated to evaluate variations among populations of Bemisia tabaci (Gennadius) from Italy and to relate their distribution to their geographic origin. Adults of the B biotype, adults of the Q-like biotype (which is similar to a Spanish biotype), and adults without esterase bands were found. The B biotype has been found in Italy since 1989. Two populations, including mainly B and Q-like biotypes, showed similar TYLCV-Sar transmission efficiency, independent of esterase banding pattern. Only populations from Liguria and Sardinia, which contained almost exclusively B-biotype individuals, were able to induce SSL. We observed that adults of the B biotype are widespread in greenhouses of northern Italy and Sardinia, whereas those of the Q-like biotype are present only in fields of southern Italy. These results suggest that the B biotype of B. tabaci was introduced into Italy likely while trading ornamental plants, whereas the Q-like biotype is native to the Mediterranean region.

Two deer fly species, Chrysops mitis Osten Sacken and Chrysops excitans Walker, were collected by sweep-netting around human bait on five collection dates in Algonquin Provincial Park, Ontario. Distribution patterns of the two species at two sites (abandoned airfield and Davies bog), in two habitats (open and forest edge), and at two times of day (morning and afternoon) are analysed. Chrysops excitans was more frequently collected than C. mitis. Regardless of site, both species are more common in the morning than the afternoon collections and both are more common in the open than the forest-edge habitats. Chrysops excitans was the larger species (based on wing length measurements) and its size was constant regardless of site, habitat, and time of day. In contrast, afternoon-collected C. mitis were larger than morning-collected flies at the Davies bog site. The crop contents of 241 flies were identified using thin-layer chromatography. Using melezitose and stachyose as honeydew-indicator sugars, the relative importance of homopteran honeydew and floral nectar as carbohydrate sources for these flies was determined. We found no significant differences among species, sites, habitats, or times of day. Overall, 52.8% of C. excitans and 51.1% of C. mitis had recently fed on homopteran-derived honeydew sugars, underscoring the importance of this carbohydrate source for the haematophagous Diptera.

Cultivars of winter wheat, Triticum aestivum L., previously identified as possible sources of resistance to wheat midge, Sitodiplosis mosellana (Géhin), were crossed with spring wheat to produce lines with a spring growth habit and assure synchrony between insect and plant. Many of the lines showed low levels of infestation by wheat midge in the field, and 21 of these were tested for resistance in the laboratory. All test lines exhibited resistance, ranging from 58 to 100% suppression of larvae and 70 to 100% suppression of seed damage, compared with a susceptible line. Larval development was delayed and survival was reduced on all lines. This antibiosis was associated with a hypersensitive reaction in the seed surface. The hypersensitive reaction, or feeding damage by young larvae before they died, reduced the biomass of some infested resistant seeds by 28% compared with over 60% for infested susceptible seeds. Some lines also reduced the level of infestation either through oviposition deterrence or a resistance which prevented newly hatched larvae from establishing on the seed surface. A few lines also reduced the hatching rate of wheat midge eggs. The resistance was equally effective in field trials during two consecutive summers in Manitoba and Saskatchewan, with at least a 20-times difference in the level of infestation between susceptible and resistant wheats. No larvae could develop to maturity on some resistant lines. Large plots of one resistant line produced less than 1% as many larvae as a typical susceptible wheat, and the larvae that did survive produced few, small adults. This resistance is the first documented case of a high level of true resistance to wheat midge in spring wheat, distinct from asynchrony between the insect and susceptible stage of the plant. The antibiosis component of the resistance is currently being incorporated in cultivars suitable for production in western Canada.

The aim of this study was to characterize polypeptide components of the capture net spun by trichopteran larvae Hydropsyche slossonae (Banks) (Trichoptera: Hydropsychidae). Thirty-one polypeptide bands were identified by SDS – polyacrylamide gel electrophoresis (SDS–PAGE) from extracted net material, with molecular weights ranging from 8500 to 179 000. Comparison with published data on Bombyx mori (L.) (Lepidoptera: Bombycidae) silk, treated under similar denaturing conditions, shows that six low molecular weight polypeptides ranging between 8500 and 18 800 in the silk of H. slossonae are absent from that of B. mori; furthermore, two high molecular weight polypeptides (210 000 and 220 000) detected in the silk of B. mori are not present in that of H. slossonae. Differences between both groups are probably related to their mode of living and to the specific use of silk (in air versus under water). Our findings are consistent with the current trend in the literature that silk spun by aquatic and terrestrial insects, as well as those spun by different species, is apparently made of different biopolymers according to the protein constituents. Hence, the polypeptide characterization of silk, combined with sequence data and (or) antibodies cross-reactivity data, could represent a potential tool for taxonomic classification improvement of aquatic insects. These results could eventually be used to characterize hydropsychid capture net anomalies induced by environmental pollution.

Third-instar larvae of Phyllophaga (s.str.) ilhuicaminai Morón and Phyllophaga (Listrochelus) cuicateca Morón and Aragón are described. Larvae of P. ilhuicaminai were taken only from the roots of Limonium sinuatum (L.) Miller (Plumbaginaceae), an ornamental herb growing in fields near Atlixco, Puebla, Mexico. Larvae of P. cuicateca were found only on roots of Amaranthus hypocondriacus L. (Amaranthaceae) in fields near Altepexi, Puebla, Mexico. These larvae cause damage to the root system of both plant species under culture. Illustrations of diagnostic structures, a brief discussion on the differences between these larvae and other Phyllophaga Harris larvae, and a key to the Mexican larvae of the genus are included.

Larvae of the wheat midge, Sitodiplosis mosellana (Géhin), feed on developing seeds of common and durum wheats, Triticum aestivum L. and Triticum durum L. (Graminae). The trophic relationships between insect and plant were quantified as biomass gains or losses using plants infested artificially in the laboratory and naturally in plots and commercial fields. The biomass of seeds from different parts of a wheat spike varied, but seeds in all parts of a spike were infested, independently of their potential biomass. Most infested seeds had 1–3 larvae, but at least 11 larvae could mature on a single seed without reducing larval biomass. When larvae finished feeding and seeds attained about one third of their biomass, specific impact varied from 4.1 to 8.5 mg of seed biomass lost for each milligram of biomass gained by a larva, with the impact declining as the number of larvae per seed increased. Specific impact rose to 100 mg/mg as seeds of T. aestivum and a primitive wheat, Triticum monococcum L., matured, and higher still for T. durum. Wheat plants did not compensate for wheat midge damage, and no indirect damage to uninfested seeds was detected. The distribution of biomass for infested seeds was bimodal, with over 40% less than 8 mg when hand harvested, whereas infested seeds harvested mechanically had a unimodal distribution, with nearly all of the most severely damaged seeds removed during harvest. A visual rating system of six damage categories was related to the biomass of the seeds. The germination and early growth rate of infested seeds were reduced compared with those of uninfested seeds. Based on the biomass relationships for the insect–plant interaction and the visual rating of damage, high-protein number 1 grade common and durum wheat and number 1 grade durum wheat can tolerate up to 6% of the seeds being infested by larvae, before downgrading is likely. For other grades, the economic threshold is 10% of the seeds infested, based on yield loss. Seed growers can adopt the threshold for number 1 wheat (6% infestation) to prevent downgrading, which would also reduce the effects of infestation on seed germination to an acceptable level.

Three white spruces, Picea glauca (Moench) Voss (30–35 cm diameter at breast height), felled in central Alberta, were colonized by Ips perturbatus (Eichhoff) beginning in late May 1999. The mean (±SE) density of breeding galleries on the trees was 217 ± 23/m2 (n = 30). Harem size ranged from one to four females per gallery, with a mean of 2.1 ± 0.6 (n = 90). Tunnel excavation and oviposition occurred primarily during the first 3 weeks after gallery initiation. Individual females laid 48.9 ± 2.5 eggs (n = 30) in galleries that reached 10.0 ± 0.3 cm in length (n = 45). Males assisted their mates by removing frass and woody debris from the tunnels. Males remained in their galleries for at least 1 week, although there was gradual attrition such that < 15% of males remained after 6 weeks. Large males abandoned their galleries sooner than small males. In contrast, females were present in almost half of the oviposition tunnels examined after 6 weeks, and there was no significant relationship between female size and residence time. Mortality from egg to adult was high (98%) during this 1-year study, likely a result of the intense crowding of galleries. Adult offspring were found beneath the bark in mid-July, although the main emergence did not begin until mid-September. Because such late emergence would be too late for these individuals to reproduce before winter, I conclude that I. perturbatus has only one generation per year in central Alberta.

The effect of semiochemical interruptants was examined for Ips latidens (LeConte) and Ips pini (Say) using artificial trees (tall-traps) consisting of an array of seven Lindgren multiple-funnel traps suspended vertically on a rope ladder. S-(+)-Ipsdienol reduced the numbers of I. latidens captured in (±)-ipsenol-baited funnel traps relative to funnel traps immediately above them and to control tall-traps. The combination of (±)-exo-brevicomin and cis- and trans-verbenol reduced the numbers of I. pini captured in (±)-ipsdienol-baited funnel traps relative to funnel traps immediately above them and to control tall-traps. These results provide support for semiochemical-based pest-management tactics that utilize a point source of interruptant at the base of a tree while noting limitations in behavioural effects and efficacy.

Random deviations from perfect symmetry in bilateral traits, fluctuating asymmetry, are thought to reflect developmental stability: the ability of an individual to buffer against genetic and (or) environmental stress during development (Palmer and Strobeck 1986). Fluctuating asymmetry is often regarded as an indicator of individual quality or fitness (Møller and Swaddle 1997); however, factors underlying fluctuating asymmetry are not well understood (Markow 1995). It has been suggested that heterozygosity, ploidy, and genomic coadaptation (hybridization) are genetic factors affecting the magnitude of fluctuating asymmetry (Palmer and Strobeck 1986; Markow 1995; Møller and Swaddle 1997). Insects having a haplodiploid sex-determining mechanism present opportunities to examine the relationship between ploidy and fluctuating asymmetry. In hymenopterans, females are diploid and males haploid. Thus the effects of ploidy can be investigated by contrasting males and females within a population (e.g., Clarke 1997). Diploid females, in which deleterious recessives reducing developmental stability could be masked, may be expected to have smaller asymmetry than haploid males (e.g., Brückner 1976; Smith et al. 1997). In this paper, we compare the level of fluctuating asymmetry in forewing venation of males to that of females in the carpenter bee Xylocopa appendiculata circumvolans Smith.

We examined the influence of temperature and release density on the root-boring moth, Agapeta zoegana L., a biological control agent of diffuse knapweed, Centaurea diffusa Lam., and spotted knapweed, Centaurea maculosa Lam. Moths were released at six densities (1, 2, 4, 8, 16, and 32 adult male–female pairs) in each of 2 years (1992 and 1993 cohorts) into outdoor, caged plots containing spotted knapweed. Air temperature, larval establishment and mass, and adult emergence, mass, and body dimensions were measured. Larval production increased linearly with adult release density in both cohorts. Larval survival ranged from 0 to 100% and was not correlated with release density or accumulated degree-days in either year. Date of first emergence occurred earlier as both release density and larvae per plant increased, but only for the 1992 cohort. Declining resources or increased contact among the larvae may induce early pupation. Peak emergence rate increased with release density in both cohorts. First emergence was related more closely to calendar date than accumulated degree-days. In contrast, peak emergence rates were more consistent with degree-day accumulations between cohorts than calendar date. Adult production increased with parental release density in both cohorts. Females were heavier, wider, and longer than males. Optimal A. zoegana production will be achieved with releases of greater than 1.6 male–female adult pairs per spotted knapweed plant.

The toxicity of dicofol, pyridaben, formetanate HCl, and abamectin to European red mite, Panonychus ulmi (Koch), was determined using either a Petri dish or leaf dip bioassay (as potential field assay procedures) and was compared with results from a standard laboratory procedure that requires a Potter spray tower to treat leaf disks. Abamectin and pyridaben were the most toxic acaricides tested, and dicofol and pyridaben were more toxic when applied to Petri dishes than to leaf disks. Formetanate HCl was the least toxic acaricide tested by either leaf disk or leaf dip procedures. Diagnostic concentrations of pyridaben were determined as 5 mg active ingredient per litre (a.i./L) with the Petri dish assay and 15 mg a.i./L with the leaf disk assay. Mortality of European red mites to pyridaben at diagnostic concentrations was consistently 100% with the leaf disk assay and > 90% with the Petri dish assay. Residues of pyridaben on Petri dishes stored at 4 °C in a refrigerator were stable for at least 21 d. For dicofol, both leaf disk and Petri dish assays gave similar results, and 25 mg a.i./L, previously used as the diagnostic concentration in the Petri dish assay, resulted in > 99% mortality of the standard susceptible strain. This technique identified resistant individuals in all of the field populations tested. Abamectin applied at 2 mg a.i./L to leaf disks consistently gave 98–100% mortality, but results at 2 mg a.i./L with the Petri dish assay gave variable results and this was not a reliable technique for monitoring resistance. Concentrations of formetanate HCl required for the leaf dip assay were too high to be useful in field assays; however, all populations of European red mite tested using the leaf disk assay appeared susceptible. For the ovicide, clofentezine, mortality of eggs tested by the leaf disk assay at 100 or 500 mg a.i./L ranged from 89 to 100%. Results with the leaf dip procedure, using a 350 mg a.i./L suspension consistently resulted in > 96% mortality of eggs from susceptible field populations. These procedures are a useful tool in the development of resistance management programs for acaricides used in integrated pest management (IPM) systems for tree fruits.

A two-choice feeding bioassay was used to investigate the effects of larval source (colony versus wild larvae) and rearing medium (artificial versus foliar diet) on the feeding-deterrent activity of the oral exudate of the spruce budworm and the western spruce budworm, Choristoneura fumiferana (Clem.) and Choristoneura occidentalis Free., respectively. Feeding by both wild and colony larvae was deterred by conspecific oral exudate. Larvae reared on artificial diet responded to exudate from both diet- and foliage-reared larvae, whereas the foliage-reared larvae responded only to exudate from other foliage-reared larvae. These results suggest that differences exist between artificial diet- and foliage-reared larvae in the composition of oral exudate, in the concentrations of its biologically active constituents, or in differential sensitivity of diet- and foliage-reared larvae to exudate from foliage-reared larvae.

Susceptibility of many insects to baculoviruses decreases with host development (Hochberg 1991), whereas the time required for infected hosts to die increases with larval age (Boucias et al. 1980; Bucher and Turnock 1983; Smits and Vlak 1988). The actual mechanism of this phenomenon, however, has not been established in many cases. The present study was undertaken to investigate the effect of larval age on the susceptibility of Spodoptera litura Fabricius to nuclear polyhedrosis virus (NPV) through oral and intrahaemocoelic routes of infection.

Dusky wireworms, Agriotes obscurus (L.), aggregated at rows of wheat, Triticum aestivum L., spaced 1 m apart within 6 d of seeding. Wireworms also aggregated at rows of newly planted strawberries, Fragaria × ananassa Duchesne, resulting in 43% plant mortality. Wheat rows planted 8 d in advance of intercropped rows of strawberries aggregated wireworms at the wheat rows rather than at the strawberry rows. Mortality of strawberry plants protected by the previously planted wheat rows was only 5.3%. Strawberry seedlings planted 14 d before intercropping with wheat rows incurred 29.6% mortality. These data show that trap crops of wheat planted 1 week in advance of planting strawberries can effectively reduce wireworm feeding and plant mortality and can be used as an inexpensive pest management method.

Bark beetles were trapped for two summers in a mature stand of lodgepole pine, Pinus contorta var. latifolia Engelmann (Pinaceae), infested by mountain pine beetle, Dendroctonus ponderosae Hopkins, near Princeton, British Columbia. Columns of flight-barrier traps were suspended next to uninfested live trees and from dead brood trees containing new adult beetles. The brood trees had been treated in the previous year with mountain pine beetle pheromone bait alone or in combination with Ips pini Say (Coleoptera: Scolytidae) pheromone bait and subsequently killed by mountain pine beetles. A total of 3376 individuals from 30 species of Scolytidae were captured in the traps. Most of the species for which lodgepole pine is a nonhost or occasional host were captured in low numbers (one or two specimens). The most abundant species (> 30 individuals) were D. ponderosae, I. pini, Hylurgops porosus LeConte, Pityogenes knechteli Swaine, and Trypodendron lineatum Olivier. The treatments affected captures of mountain pine beetles and I. pini but only in the year when trees were either unbaited or baited simultaneously for mountain pine beetle and I. pini. There were significant differences among the five most abundant species in the mean heights and mean Julian dates of capture. In addition to host condition requirements, these differences reflected partitioning of the food and habitat resource and competitive interactions among species. There was no interaction between treatment and trap height, indicating that treatment did not affect the height distribution of flying beetles.