The wheat midge, Sitodiplosis mosellana (Géhin), infests wheat, Triticum aestivum L., heads only up to anthesis when pollination occurs. The termination of infestation might be due to a deterrence of oviposition or to a suppression of larval growth on developing seeds. These hypotheses were tested in the laboratory by measuring oviposition preference, larval development, and larval preference for plants at different growth stages. Females showed no preference for ovipositing on heads at any stage from the onset of heading up to and including anthesis, and continued to lay eggs at a reduced rate 10 days after anthesis. Survival of newly hatched larvae was reduced on seeds 3–1 days after anthesis and survival and development was greatly reduced on seeds 5 or 6 days after anthesis. Larvae moved away from older seeds and fed on younger seeds in a choice test. Given a hatching time of 5–6 days, a failure to infest wheat after anthesis is not due to oviposition deterrence at anthesis, but to suppression of larval growth and development which begins soon after anthesis.

Using alternating patches of weeds and crop [broccoli, Brassica oleracea (L.) (Brassicaceae)], vegetation composition and the spatial scale at which the vegetation was fragmented were manipulated in a factorial design field experiment. The effects of these manipulations were different for two common agroecosystem predators sampled. Sevenspotted lady beetles, Coccinella septempunctata (L.), were unaffected by vegetation-composition treatments but responded strongly to fragmentation-scale manipulations. The beetle Pterostichus melanarius (Illiger) was unaffected by both fragmentation-scale and vegetation-composition manipulations. These findings highlight the challenge of developing a predictive theory of the effects of vegetation diversification on assemblages of predators in agroecosystems.

The wheat midge Sitodiplosis mosellana (Géhin) occurred in all wheat-growing areas of Manitoba during 1993–1997, with 95% of spring wheat fields having some seeds infested by larvae. The level of infestation varied, but each year in excess of 20% of seeds were infested in some fields. Infestation levels in adjacent fields were more similar than in fields separated by a few kilometres. Within fields, the infestation was similar at the edge and near the centre. Wheat midge larvae also overwintered in, and adults emerged from, fields in all wheat-growing areas of Manitoba. Adults emerged from the end of June to the end of July most years, and the peak period for adult flight was mid-July, about 1 month later than in parts of Europe where winter wheat predominates. The timing of the emergence was similar from place to place and year to year. Females constituted 95% of insects caught in a flight trap. The first 10% and 50% of the flight occurred on 9 and 16 July, respectively, and the timing of the flight was not related to growing degree-days. In early August, mature larvae began dropping from wheat heads. The timing of infestation of spring wheat was variable among years because of differences in timing between midge flights and the susceptible heading stage of the crop. Nevertheless, the wheat midge flight usually coincided with the susceptible stage of the spring wheat crop.

Extraction of DNA from whole aphids, in combination with random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) (Williams et al. 1990) markers can detect interspecific and intraspecific genetic variation (Black et al. 1992; Cenis et al. 1993). However, these techniques entail destructive sampling of fresh or preserved specimens. To allow experimental replication from a single sample while preserving the same aphid for morphometrical or karyotyping analyses, we describe a technique for RAPD-PCR using DNA from single aphid embryos. We evaluated the usefulness and reliability of single-embryo analysis, using four species of our laboratory colonies, namely Acyrthosiphon pisum (Harris), Aphis fabae Scopoli, Aphis frangulae group, and Aphis gossypii Glover.

Larvae of the hemlock looper, Lambdina fiscellaria fiscellaria (Guenée) (Lepidoptere: Geometridae), consume both new and old foliage within the crowns of their host, balsam fir, Abies balsamea (L.) Miller (Pinaceae), despite the poor nutritional quality generally ascribed to old tissues. Laboratory studies evaluated whether the consumption of old foliage by hemlock looper larvae could be an adaptation to the relative paucity of new versus old foliage, and to the limited temporal window during which young foliage remains high in nutritional quality. Access to new foliage was critical to hemlock looper survival; 55% of larvae fed an exclusive diet of new foliage survived, whereas only 5% and 0% of larvae fed exclusively 1-or 2-year-old foliage survived, respectively. Moreover, larvae reared on branches in synchrony with bud flush were more than twice as likely to survive than those whose emergence was delayed by 2 weeks. Despite the reliance by the hemlock looper upon new foliage for survival, larvae given access to both new and old foliage survived better and were heavier than those restricted to new foliage. By incorporating older foliage into their diet, the hemlock looper can circumvent the limited availability of new foliage, thereby gaining access to more abundant tissues.

A 2-year field study was carried out to determine densities and stage-specific survival of eggs, second- and third-instar larvae, prepupae, pupae, and adults of Strobilomyia appalachensis Michelsen in a black spruce, Picea mariana (Mill.) B.S.P. (Pinaceae), seed orchard located in New Brunswick, Canada. Trends in stage-specific survival were similar for both years. Most individuals died during the second-instar stage, we suspect mostly because of failure to establish. The lowest stage survival occurred during the prepupal and pupal stages, due primarily to predation by ground-dwelling invertebrates.

A laboratory experiment was conducted to identify the overwintering stage of the fir coneworm, Dioryctria abietivorella (Grote), in eastern Canada and determine the influence of photoperiod on diapause induction. In another experiment, different developmental stages were exposed to field conditions to evaluate their capacity to survive the overwintering period. Insects were either placed in the duff or exposed to ambient (above ground) conditions to assess the importance of overwintering site on winter survival. Exposure of the fir coneworm to constant short-days or a daily decreasing photoperiod during larval development induced almost all insects to initiate diapause at the fifth instar. Third-, fourth-, and fifth-instar larvae survived the overwintering period when placed in the duff. Because the fir coneworm must leave its host tree and drop to the ground to avoid rigorous winter conditions, we concluded that only fifth-instar larvae could resume development in spring using such a strategy.

(E)-9-Dodecenyl acetate (E9-12:OAc) and (Z)-9-dodecenyl acetate (Z9-12:OAc) are major components of the sex pheromone of the cherry bark tortrix (CBT), Enarmonia formosana (Scopoli), in British Columbia. The compounds were identified in extracts of female pheromone glands by coupled gas chromatographic – electroantennographic detection (GC–EAD) and coupled GC – mass spectrometry. In field experiments, traps baited with E9-12:OAc or Z9-12:OAc singly were unattractive to male CBT, but in combination at ratios of 50:50 or 40:60 captured numerous males. Increasing quantities of this two-component pheromone blend resulted in increasing captures of male CBT. This binary blend at a 10-mg dose caught more CBT males that did caged virgin CBT females. Eight other EAD-active acetates identified in extracts of pheromone glands failed to enhance attractiveness of the pheromone blend. These compounds may serve to reduce cross-attraction of heterospecific male moths or may play a role in courtship behaviour. Formulations of synthetic pheromone are being evaluated for management of the CBT using mass trapping or disorientation of male CBT moths.

Dendrocerus carpenteri (Curtis) was reared in the laboratory on prepupae of Aphidius ervi Haliday (Hymenoptera: Braconidae, Aphidiinae) developing in pea aphid, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). To test alternative hypotheses about host-marking behaviour and discrimination, we transferred unparasitized and previously parasitized A. ervi prepupae from donor to recipient mummies, which were either "unparasitized" or "parasitized." Females accepted already parasitized hosts within unparasitized mummies, but they rejected unparasitized hosts within previously parasitized mummies. Host discrimination was not influenced by self and conspecific parasitism. Eggs were frequently placed directly on the mummy shell, rather than on the primary parasitoid, or on dummies made from dental wax. Prepupae removed from their mummy shell were not accepted for oviposition. We propose that the "search template" of D. carpenteri is defined, primarily, by the aphid mummy, which is being marked with a contact pheromone after oviposition.

Fourteen species of parasitoids (13 hymenopterans, 1 dipteran) were reared from larvae or pupae of the obliquebanded leafroller, Choristoneura rosaceana (Harris), collected from commercial raspberry fields in the Fraser Valley, British Columbia, Canada, over 3 years. Levels of parasitism ranged from 5 to 15%. Among these 14 species, five represent new host records. A polyembryonic wasp, Macrocentrus nigridorsis Viereck (Hymenoptera: Braconidae), was the most abundant parasitoid. External feeding on the final host instar is obligatory for M. nigridorsis to complete development. On average, each parasitized host larva produced about 36 M. nigridorsis, in either unisexual or mixed-gender groups. Overall male to female sex ratio was 1:4. Head capsules of mature parasitized host larvae were significantly larger than those of unparasitized ones, suggesting that C. rosaceana larvae parasitized by M. nigridorsis might have an extra larval stage.

A study was undertaken to determine aspects of the life history, behaviour, and host plant feeding preferences of Ceutorhynchus neglectus Blatchley, a minor pest of canola, Brassica napus L. and Brassica rapa L., in western Canada. The final-instar larva was described for the first time. Ceutorhynchus neglectus was univoltine, with adults first occurring on host plants in early June. Mating occurred throughout June and July, and eggs were laid into the distal ends of developing siliques of flixweed, Descurainia sophia (L.) Webb (Brassicaceae). Mate guarding behaviour was observed for males of C. neglectus, which remained attached to females long after copulation was completed and, if necessary, struggled with rival males to prevent them from fertilizing their mates. Larvae fed upon developing seeds and, when mature, bored through the pods, dropped to the soil, and constructed earthen cells approximately 2 cm beneath the soil surface where they pupated. Results from laboratory host preference studies were consistent with field observations which indicated that among selected species of Brassicaceae, leaves and siliques of D. sophia were preferred by adults of C. neglectus as feeding sites. In contrast to flea beetles, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), which fed indiscriminantly over the entire cotyledon surfaces of canola seedlings, adults of C. neglectus caused less cotyledon damage per individual and tended to feed on cotyledon edges. Because of its biology and host plant preferences, C. neglectus should remain a minor pest of canola, and can only be expected to invade the crop when its preferred host (flixweed) is unavailable.

The forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), is subject to a variety of naturally occurring infectious diseases, including a nuclear polyhedrosis virus (MdNPV) which has been observed to reach epizootic proportions (Stairs 1966; Myers 1993).

Because MdNPV is currently available only in limited quantities for small-scale experimentation, production scale-up is vital to it's potential as a biological control agent against the forest tent caterpillar. Viruses replicate only in living cells, therefore it is necessary to produce viral insecticides either in host insect larvae (in vivo) or in susceptible cell cultures (in vitro). Insect cell cultures have not yet been developed so that large-scale production of baculoviruses are feasible (Cunningham 1995), thus in vivo production must be used. To plan for the scale-up of NPV production, it is necessary to establish the yield of occlusion bodies (OBs) from M. disstria larvae. We report here the yield of OBs from four larval instars inoculated with MdNPV, the time to mortality, head capsule widths, and body weights, and recommend larval instars suitable for further research toward commercial-scale production.

Variation in bark beetle attack following spacing of mature lodgepole pine stands in the East Kootenays of British Columbia was analyzed in relation to stand location (site), spacing treatment, and harvesting injury. Observations were made on three sites, each having three treatments: 4 × 4 m spacing, 5 × 5 m spacing, and untreated control. There was no statistically significant difference in the numbers of attacked trees among sites or treatments. However, in the spaced plots 94.3% of the attacked trees sustained harvesting injury or were located adjacent to skid trails. Dendroctonus valens LeConte was the dominant species attacking trees on the two drier sites, and Dendroctonus murrayanae Hopkins was the dominant species on the third site. There was no statistically significant variation in the percentage of attacked stumps among sites or spacing treatments. On average, 80.7% of the stumps were attacked; attacked stumps had larger diameters than unattacked stumps. Thirteen species of bark beetles were found attacking stumps. Hylurgops porosus LeConte was the most numerous species at all three sites. Based on the fit of the Michaelis–Menten equations to species accumulation curves, an estimated 76–90% of the number of species attacking stumps at the three sites were observed in bark samples. Margalef’s index of diversity for the two drier sites (Cranbrook = 1.15, Parson = 1.13) was nearly identical and higher than at the moist site (Elkford = 0.89). Pairs of sites had five to six species in common, and the Sorensen coefficient of similarity ranged from 0.52 to 0.71, indicating moderate similarity in species composition. The abundance versus species rank relationship was fitted by three models: the MacArthur broken stick model, the geometric series, and the Zeta distribution. The latter gave good fit to data from two sites, but none of the fitted models gave satisfactory fit to data from the third site, mainly because of the high abundance of the second ranked species (Orthotomicus caelatus Eichhoff). Our results indicated that stand characteristics affected species assemblages and abundances of bark beetle species that attacked stumps. Management practices that minimize injury to trees during the spacing operations are emphasized to reduce attack by bark beetles.

The parasitoid Sinophorus megalodontis Sanborne is a univoltine endoparasitoid that attacks larvae of the pine false webworm, Acantholyda erythrocephala (L.). The morphologies of the egg, instar 1, and cocoon are described. Adult-emergence and Malaise traps were used to examine the patterns of adult activity in Ontario. Adults emerged from the soil over 17 d, in late May and early June, and the median emergence of males preceded that of females by 3.5 d. The sex ratio of emerging adults was approximately 1:1. Malaise traps collected more adults than did emergence traps and also provided information on adult flight period, but collections were biased towards captures of males. Dissections indicated that S. megalodontis oviposited in all instars of the host and that temporal and spatial variations occurred in coincidence with host instars. Encapsulation and superparasitism limited effectiveness of the parasitoids in reducing host populations. At the end of the larval period, the parasitism rate was 17.1%, but encapsulation reduced the effective rate to 9.0%. Superparasitism was observed in 4.8% of the host larvae. There was some indication that parasitism resulted in retardation of host development. Later-dropping host larvae had a significantly greater incidence of parasitism. The host is an introduced insect from Europe, whereas the parasitoid is likely endemic to North America. Few North American parasitoids attack this introduced species, and S. megalodontis appears limited in its ability to reduce the size of pine false webworm populations. Consequently, pine false webworm is a suitable candidate for classical biological control attempts with introduced parasitoids from Europe.

The suitability of three potential host plants, Solidago canadensis L. var. canadensis (Asteraceae), Solidago graminifolia (L.) Salisb., and Aster lateriflorus L. (Asteraceae), for the goldenrod beetle, Trirhabda virgata LeConte was determined by measuring several fitness components during the T. virgata life cycle. Neonate larvae were collected from S. canadensis plants and transplanted onto S. canadensis, S. graminifolia, and A. lateriflorus and maintained in field enclosures until the last instar was reached. Once brought into the laboratory, larvae were fed their assigned host plant until pupation. Following emergence, adults were weighed and separated into mating pairs to record oviposition and longevity. Eggs were kept in the laboratory until the following spring, when first instar larvae were taken into the field and re-established on their assigned host, and the experiment was repeated for 2 years. Larval survival and rate of development was not affected by the host plant. Mean weight of adults at emergence was greater on S. canadensis than on either S. graminifolia or A. lateriflorus. Two components of adult fitness, postmating longevity and realized fecundity, were measured. Longevity of adult female T. virgata was not affected by the host plant. Fecundity of T. virgata reared on A. lateriflorus and S. graminifolia was lower than the fecundity of females reared on S. canadensis. These results are consistent with the hypothesis that both intrinsic plant quality and the mobility of the foraging stage are important in the evolution of host range in T. virgata. These experiments were repeated over a 3-year period, using offspring from the survivors of the previous year for the 2nd and 3rd years. Over this time, individuals experienced "laboratory adaptation," and both accepted and increased their performance on previously unacceptable food plants.

Natural mortality of gypsy moth [Lymantria dispar (L.) (Lepidoptera: Lymantriidae)] eggs, larvae, and pupae was examined at several locations along a gradient of infestation in Ontario, Canada. Most mortality of eggs was the result of exposure to winter weather. This mortality was mitigated in egg masses located near ground level where they benefited from snow cover. At least six species of parasitoids were found attacking gypsy moth larvae and pupae. The most common species were present in the same rank order of abundance at all sites. Identified pathogens were also present in most sites but their relative abundance varied greatly. The mycopathogen Entomophaga maimaiga Humber, Shimazu & Soper (Zygomycetes: Entomophthorales) was found at all sites and usually was responsible for the highest levels of observed, single-source mortality at the site.

At Alexandra Fiord, Ellesmere Island, the diving beetles Hydroporus morio Aubé and Hydroporus polaris Fall occur in a series of shallow ponds. Detailed habitat measurements of a temporary and a permanent pond revealed a more complex and extensive organic substrate and vegetation community, longer developmental time, and greater thermal budget in the permanent pond. Hydroporus polaris was most abundant in the temporary pond, but occurred in both; this species oviposited in the absence of macrophytic vegetation, completed larval development quickly, and pupated in the drying pond substrate, and adults dispersed in fall to moister overwintering sites. Hydroporus morio was restricted to the single permanent pond; this species took longer to complete larval development, pupated in wet moss, and overwintered as adults encased in ice on the vertical pond edge. We hypothesize that H. morio is excluded from temporary ponds in the arctic by its requirement for a relatively long development time. Alternatively, H. morio may require sheltered overwintering sites that temporary ponds do not offer.

The potential for pheromone-mediated mating disruption of the cherry bark tortrix (CBT), Enarmonia formosana (Scopoli), was evaluated by attaching PVC tube dispensers to the trunks of mature (> 40 cm diameter at breast height) ornamental cherry trees, Prunus cvs., lining suburban streets of New Westminster and Vancouver, British Columbia. Dispensers released either a blend of (E)-9-dodecenyl acetate (E9-12:OAc, 49.5%), (Z)-9-dodecenyl acetate (Z9-12:OAc, 49.5%), and (Z)-7-decenyl acetate (Z7-10:OAc, 1%) at a rate of 29 mg/day (Exp. 1), or E9-12:OAc alone at 27 mg/day (Exp. 2), 4 mg/day (Exp. 3), or 0.5 mg/day (Exp. 4). A sticky Delta trap baited with a grey rubber septum impregnated with CBT pheromone components E9-12:OAc (40 μg), Z9-12:AOc (60 μg), and Z7-10:OAc (1 μg) was placed in each tree. Captures of male CBTs in treatment trees were significantly reduced compared with control trees in all experiments. Results suggest that disruption of pheromone-based communication in CBT around individual cherry trees is feasible with a pheromone blend or with E9-12:OAc alone, and could become part of an integrated management strategy for CBT in urban environments.

Cyphocleonus achates (Fahraeus) is a weevil used for the biological control of diffuse knapweed, Centaurea diffusa Monnet Del La Marck, and spotted knapweed, Centaurea maculosa Monnet Del La Marck, in North America. This research provided specific information on the biology of this insect in British Columbia. Adult weevils were released at six densities (1, 2, 4, 8, 16, and 32 male–female pairs) in each of 2 years into plots containing spotted knapweed. Larvae per plant, larval mass, larval survival, adult emergence, and air temperature were measured. Larval production increased with the release density of weevils in both the 1992 cohort and the 1993 cohort. Larval mass did not differ between years. Larval mass also did not vary with the release density of adults or the number of larvae per root. Larval survival of the 1993 cohort ranged from 17 to 48%, whereas that of the 1994 cohort ranged from 0 to 91%. Adult emergence began after the accumulation of 726–1144 degree-days. For both cohorts the date of first emergence occurred earlier, as the average number of larvae per plant increased for both cohorts. Increasing competition for food or space in the roots can induce early emergence. Sex ratios did not vary with date of emergence or release density of adult weevils. Adult emergence increased with the release density in the 1992 cohort, suggesting the average larval densities did not exceed the carrying capacity of the roots. The peak emergence rate increased with the release density in the 1992 cohort, but not in the 1993 cohort because of lower larval survival.

The research objective of this study was to develop a pheromone-based detection system for the nun moth, Lymantria monacha (Linnaeus), an important defoliator of spruce, Picea A. Dietrich, and pine, Pinus Linnaeus (Pinaceae), forests in central Europe. In northeastern Germany, comparative analyses of rubber- and polyurethane-based dispensers impregnated with a 20:20:1 blend of (±)-disparlure (cis-7,8-epoxy-2-methyloctadecane), (±)-monachalure (cis-7,8-epoxy-octadecane), and 2-methyl-Z7-octadecene revealed that polyurethane-based dispensers afforded higher captures of male L. monacha. Species specificity and optimal dose of the pheromone dispenser were tested in deciduous rather than coniferous forests in central Europe to better reflect nonhabitat settings, such as North American ports, in which detection surveys would be conducted. Baiting Unitraps with 2, 20, 200, or 2000 μg [based on (±)-disparlure] of the L. monacha volatile blend resulted in increasing, species-specific captures of male L. monacha with increasing volatile dose. (±)-Disparlure, previously used for detection of L. monacha, tested at the same four doses indiscriminately attracted male L. monacha and male Lymantria dispar (Linnaeus). Polyurethane-based dispensers loaded with at least 200 μg of the L. monacha volatile blend are recommended for sensitive detection surveys of L. monacha in North America.