Vesicas of the following tortricid and other small lepidopterous species are described and illustrated: Tortricidae: Orthotaenia undulana (Denis and Schiffermüller), Apotomisfrigidana (Packard), Olethreutes appendiced (Zeller), Evora hemidesma (Zeller), Epinotia nanana (Treitschke), Corticivora clarki Clarke, Atchips packardiana (Fernald), Pandemis limitata (Robinson), and Aethes rutilana (Hübner); Oecophoridae: Psilocorsis quercicella Clemens; Gelechiidae: Dichomeris flavocostella (Clemens); and Nepticulidae: Obrussa ochrefasciella (Chambers).The injection and chemical induction techniques of eversion of vesicas of tortricid moths and other Lepidoptera are described.

The life history, behaviour, and mortality of the western ash bark beetle, Hylesinus californicus (Swaine), was investigated in green ash, Fraxinus pennsylvanicus var. subintergerrima (Vahl) Fern., in Calgary, Alberta. This species is univoltine with an apparent obligate diapause in the adult (overwintering) stage. Adults emerge from overwintering sites in the bases of ash boles from mid-April to mid-May and fly or walk up the bole to the crown where maturation feeding, mating, and reproduction occur. Eggs are present by late April, larvae by early May, pupae by mid-July, and new adults by late July. There are three larval instars. Beetles emerge from larval galleries in August and enter fresh phloem in uninfested parts of branches to feed for up to 6 weeks. Beetles leave feeding galleries from mid-September to early November and migrate by walking, falling, and flying to overwintering sites in the base of ash boles. Total mortality from egg to eclosed brood adult was 80.6%. Disease, parasitoids, and dehydration were the main causes of mortality. Eight hymenopterous parasitoid species were identified; the pteromalid wasp Rhaphitelus maculatus Walker was the most abundant. Tree hazard rating, maintenance of tree health, removal of susceptible and infested host material, and application of pesticides are suggested for management of western ash bark beetle populations.

A 4-year field cage study was conducted to determine what effects feeding of alfalfa plant bug, Adelphocoris lineolatus (Goeze), late in the season had on alfalfa seed yields. When zero, one, two, or four alfalfa plant bugs were placed in sleeve cages containing stems of alfalfa at the green pod stage of growth, there was a significant decrease in the number of pods per cage and per raceme, the number of healthy seeds, and the weight of seeds with two or four bugs per cage. Increasing the duration of infestation resulted in significant increases in the number of damaged seeds per cage. An insecticide field trial was conducted in north central Saskatchewan in 1988 to determine what effects the occurrence of plant bugs had on seed yields of alfalfa. Alfalfa plant bug, lygus bug (Lygus spp.), pea aphid [Acyrthosiphon pisum (Harris)], and beneficial arthropod populations were monitored from 23 June to 1 September 1988. Seed yields were significantly greater in plots that were treated with trichlorfon in June and in June and August than in plots that were treated in August alone. The implications of a large alfalfa plant bug population late in the season to alfalfa seed production in the area are discussed.

Microplitis mediator (Haliday), a braconid parasitoid reared on the bertha armyworm, Mamestra configurata (Walker), entered diapause at 16 °C and a 12L:12D (100%) or 14L:10D photoperiod (99%) but not at 16 °C or 21 °C under a 16L:8D photoperiod or at 21 °C and a 12L:12D photoperiod. Diapause development was accelerated by cold treatment; adults emerged from diapause more rapidly with increasing duration of cold exposure at least up to 120 days. The main pupation site was found to be on senescent canola leaves which formed a leaf litter on or near the plants. Nearly all unparasitized fourth-instar hosts (98–100%) were found on host plants, whether the conditions induced diapause or not. Only 16–23 and 0% of parasitoids pupated on host plants under conditions of non-diapause or diapause induction, respectively. Because the pupation site of the parasitoid depends on movement of the host, these results suggest that mature parasitoid larvae modify movement of their host.

Populations of the lesser clover leaf weevil, Hypera nigrirostris (Fabr.), on red clover, Trifolium pratense L., in northeastern Saskatchewan were sampled weekly from May to August 1986 and 1987. Adults overwintered in red clover fields, and began to feed, mate, and oviposit in late April and early May. Eggs were laid subepidermally in stipules, shoots, and leaves from early May to mid-July. Larvae were located on red clover stipules, buds, and fiowerheads and developed through four instars Larvae were collected from early June until mid-August. Spatial distributions of eggs and larvae were aggregated, though the degree of aggregation decreased with succeeding developmental stages. Pupae were collected on shoots and in debris from late June until August. New-season adults first occurred in mid-July; large increases in adult densities corresponded to the appearance of these adults.

Initially, fenvalerate and permethrin tags at two tags per animal and one tag for every other animal nearly eliminated horn flies [Haematobia irritons (L.)] at Glenlea Research Station, Manitoba. However, fly numbers increased 8 weeks post-treatment in 1987 and 6 weeks post-treatment in 1988. LC50 values of the flies to fenvalerate and permethrin increased toward the end of each season but the slope of regression lines decreased in 1987. In 1988, initial LC50 values were lower compared with those observed at the end of the 1987 season. When tags were applied in 1988, LC50 values increased from 0.42 to 3.14 μg per cm2 for fenvalerate and from 2.06 to 10.76 μg per cm2 for permethrin. Mortality observed at discriminating concentrations of fenvalerate (0.625 μg per cm2) and permethrin (5 μg per cm2) during the season decreased from 67.9 to 2.8% and from 66.8 to 5.7%, respectively. Cattle at Glenlea and in a second herd at Libau were not treated in 1989; susceptibility of flies resistant to pyrethroids did not change significantly during the season in these herds. Discontinuing use of pyrethroid-impregnated ear tags for one season was not long enough for substantial reduction in resistance to occur.

North American members of the Oreodyies alaskanus clade are revised. The species O. productotruncatus (Hatch) and O. recticollis (Fall) are recognized as valid and those names are removed from junior synonymy with O. alaskanus (Fall.). Oreodytes leechi Zimmerman is considered a new junior subjective synonym of O. recticollis. Lectotype designations are provided for O. alaskanus and O. recticollis. Palaearctic O. dauricus (Motschulsky) is included within the O. alaskanus clade whose members are characterized by the protibia having the inner margin sinuate and strongly narrowed proximally, Oreodytes kanoi Kamiya, from Japan, is suggested as the sister-group of members of the O. alaskanus clade based on the shared presence in the female of a last abdominal sternite with an emargination at the apex.

Pterin accumulation in response to temperature and time was studied in male and female stable flies Stomoxys calcitrans (L.). Pterins accumulated as a function of temperature integrated over time. The threshold for pterin accumulation was estimated at 6.5 °C. The relationship between pterin content (RF/mm head capsule width) and accumulated degree-days above 6.5 °C (DD6.5) was determined to be RF/mm = 38,06 + 1.258*DD6.5 for females and RF/mm = 37.65 + 1.765*DD6.5 for males. Ovarian development, measured by follicle length and degree of vitellogenesis, was also related to DD6.5 and pterin concentration. The relationship between y1 = follicle length (mm) and x = DD6.5/200 was y1 = 0.11 + 0.78* [1−exp(− 18.34*x)]**99.86 and between vitellogenic stage (y2) and x was y2 = 0.04 + 3.96*[1−exp(− 11.48*x)]**6.67. Stable flies had a temperature threshold of 8 °C for oviposition.

Increased seed yields often result when alfalfa fields are burned in spring. The main pollinator of seed alfalfa in Alberta is the alfalfa leafcutter bee, Megachile rotundata (F.), that cuts pieces of leaves to build thimble-like cells. One hypothesis for increased seed yield is that alfalfa leaves from burned fields may be easier for the bees to cut. Cutting of leaf pieces causes progressive wear to the mandibles, which could decrease bee efficiency, resulting in reduced pollination and lower seed yields. An image analysis method was used to measure the mandibular wear of leafcutter bees from burned and unburned alfalfa fields. No consistent difference in the amount of wear between bees foraging in burned or unburned fields was found.

Adult Calosoma sycophanta L. (Carabidae: Coleoptera) male and female pairs in a laboratory arena were observed for up to 30 days with a video recorder. Beetles were visible (i.e. not hiding) or in soil (i.e. female ovipositing) especially during night hours. Feeding on gypsy moth larvae occurred any time of the day or night. Male and female beetles were most active during the time when female beetles were ovipositing. Females spent more time eating and staying in soil than did males, but males tended to move around the arena more than did females. Based on results from this study, it is expected that, in the forest, C. sycophanta females will spend most of their time hidden in leaf litter or ovipositing. Males are more likely to be seen because they spend more time moving about, probably seeking mates.

A method of assessing susceptibility of white fir, Abies concolor (Gord. and Glend.) Lindl., by fungal inoculation was tested during an outbreak of the fir engraver beetle, Scolytus ventralis LeC., at Lake Tahoe, California, in 1987 through 1989. A total of 592 firs growing in six forest stands containing trees infested by the beetle were inoculated with the mutualistic fungus, Trichosporium symbioticum Wright. Six weeks later, reaction wounds were characterized by vertical length and resin concentration. After 2 years, 196 (33.1%) of the test firs had been killed by the beetle. Reaction lengths tended to be greater and resin concentrations lower in test firs that died than in those that survived, but predictive accuracy of the wound variables was inadequate on either an individual tree or a stand basis. On an individual tree basis, discriminant functions using either or both of these reaction wound variables as predictors produced overall percentages of correct classification little higher than would be obtained by predicting that all test firs would survive. On a stand basis, regression models using stand means for the wound variables and white fir basal area as predictors statistically explained more than 95% of observed variation in basal area of white fir killed, but another model using only basal area of white fir as a predictor performed nearly as well.

Laboratory experiments were conducted to determine the effect of wounding the cotyledons of Sinapis alba L. cv. Ochre, Brassica napus L. cv. Westar, B. rapa L. cv. Tobin, and C8711, a selection from Tobin, on subsequent feeding damage by the flea beetle, Phyllotreta cruciferae (Goeze). Cotyledons of 7-day-old seedlings were wounded either by puncturing them with needles (mechanical wounding) or by exposing them to flea beetles. One, 2, or 9 days following wounding, the wounded and unwounded seedlings were exposed to flea beetles and the feeding damage was estimated as a measure of antixenosis. Mechanical wounding of one of the cotyledons with 96 needle punctures induced a significant reduction in the damage of the unwounded cotyledons of S. alba, 1 or 2 days following wounding. True leaves of the wounded seedlings also showed consistently less damage than unwounded controls, 9 days following wounding. In S. alba, all three levels of mechanical wounding (i.e. 6, 24, or 96 punctures per cotyledon) reduced subsequent flea beetle damage to a similar extent. Wrapping a cotyledon of S. alba with a plastic film produced an effect similar to wounding it with needles. As with mechanical wounding, flea beetle wounding also reduced subsequent flea beetle damage in S. alba. Other plant species (B. napus and B. rapa) tested showed no measurable induced effects on subsequent feeding damage.

The discovery of the European dandelion leaf-gall midge, Cystiphora taraxaci (Kieffer, 1888) (Diptera: Cecidomyiidae), in north-central Saskatchewan, Canada, on dandelion, Taraxacum officinale Weber (Asteraceae), is reported. This is the first record of this insect in North America. Cystiphora taraxaci is similar to Cystiphora canadensis Felt which produces galls on rattlesnake-root, Prenanthes spp., and is known only from females. Separation of the two species was achieved by demonstrating that C. taraxaci produced galls on dandelion but not on Prenanthes spp. The identity of C. taraxaci was confirmed by comparison of specimens collected in Saskatchewan with those in Europe. In Saskatchewan, C. taraxaci occurs over at least 12 000 km2 and is parasitized by Aprostocetus sp. near atticus Graham and Crysonotomyia spp. (Hymenoptera: Eulophidae).

Individual variability in the flight potential of Ips sexdentatus Boern. was investigated using flight mill experiments. Non-flyer status and flight durations were studied in relation to day of emergence, sex, pronotum width, dried body weight (after lipid ether extraction), and lipid content estimate. Lipid content estimation was determined in beetles reared on the same trees and under identical conditions as the flight test insects.The four flight-tested cohorts showed that approximately one-third were non-flyers. The distribution of individual flight durations was described by a log-normal curve. Consequently, the dispersal variability within the population could be fitted to a linear model on a log-probit scale. The concept of FD50 (flight duration 50), defined as the flight duration of 50% of a sample population, was used to describe population flight potential.There was no significant correlation between the individual flight duration and the day of emergence, sex, body size or weight, or lipid content estimate. A significant positive correlation was recorded between the different classes of flyer (i.e. non-, short, long, and very long flyers) and the average lipid content estimate. It was hypothesized that (1) a minimum threshold fuel supply was necessary to initiate the dispersal flight and (2) fuel supply could result in dispersal tendencies representing a specific response to habitat constraints.

The family Acroceridae (Insecta: Diptera; "Small Headed Flies") are a seldom seen yet cosmopolitan group of endoparasitoids of spiders. Recent host and distribution records are presented here for six species of acrocerids: Ogcodes borealis Cole, 1919; Ogcodes pallidipennis (Loew, 1866); Opcodes sp.; Acrocera bimaculata Loew, 1866; Turbopsebius sulphuripes (Loew, 1869); and Exetasis eickstedtae Schlinger, 1972. New hosts for each fly species are; O. borealis—Schizocosa rovneri Uetz and Dondale, 1979, Pardosa spp.; O. pallidipennis—Schizocosa rovneri, Schizocosa spp.; OgcodesSp.—Anyphaena californica (Banks, 1904); Acrocera bimaculata—Coras montanus (Emerton, 1890b); T. sulphuripes—C. montanus.Detailed field measurements and behavioral observations of host spiders and fly development are described and compared with known data. Examination of these comparisons suggests that host–parasitoid relationships follow spider guild associations (i.e. ground/surface dwelling hosts or those building webs in close contact with surfaces), especially with the spider family Agelenidae. These affiliations probably result from a combination of the spider’s web building, web maintenance, hunting behaviors, and fly oviposition activities, which dispose spiders exhibiting these behaviors to greater chances for parasitoidism. These factors act in concert to increase probabilities for host–parasitoid interactions. Compiled data indicate duration of pupation may be related to ambient temperature. Evidence is presented that acrocerid larvae may alter their hosts’ behavior to increase the parasitoids’ probability of survival.

Thermal responses and temperature-dependent development of laboratory- and field-overwintered eggs of the fruittree leafroller, Archips argyrospilus (Walker), were described using data from constant-temperature laboratory experiments. The time required for completion of hatch of overwintering eggs declined throughout winter until the end of January, after which increasing exposure to natural or artificial cold conditions had minimal effect on median hatching time. There was little year to year variation in response to cold treatments, and thus it was concluded that diapause is terminated by 1 February. Time to hatch decreased with increasing temperature. Distributions of hatch times were near normal, with mean and median development times similar at any given temperature. Development time (days ± SD) at a mean temperature of 20 °C was similar under constant (10.7 ± 1.1) and fluctuating (9.1 ± 1.4) temperature regimes. A nonlinear, six-parameter, biophysical model, fitted (r2 = 0.99) to median hatching rates at 11 temperatures (0.5–30 °C) indicated development was nonlinear below 10 °C, increased linearly between 10 and 25 °C, was maximal at 27.5 °C, and decreased above 27.5 °C. The lower developmental threshold (± SE), estimated to be 4.95 ± 0.54 °C by linear regression (r2 = 0.98) and the x-intercept method, was used to construct a degree-day (DD) model for predicting egg hatch. Median egg development required 154 DD above 4.95 °C. Observed median egg hatch in two different field sites and years was within ± 3 days of the predicted date, using max–min air temperatures, a base temperature of 5 °C, and a starting date of 1 February for accumulating DD. This model should prove useful for scheduling management actions against fruittree leafroller on apples and pears.

We evaluated host discrimination and oviposition restraint in the wasp Praon pequodorum Viereck, a solitary parasitoid of the pea aphid, Acyrthosiphon pisum (Harris). In dichotomous preference tests, wasps attacked more unparasitized than equally available parasitized aphids, and more self-parasitized aphids than aphids parasitized by conspecific females. The conditional probability of a female laying an egg into an attacked aphid was independent of the host type. Host discrimination apparently involves a volatile and individual-specific pheromone marker. Females expecting to compete with other (conspecific) wasps for a limited host supply may ensure possession of the host by self superparasitism. Because host examination requires considerably more time than oviposition in P. pequodorum (and eggs contain few resources), it may be adaptive for a female to lay an egg in an examined host regardless of variations in host quality.

New records for non-indigenous species of Hemiptera: Heteroptera continue to be reported from Canada. Schwartz et al. (1991) reported the microphysid Loricula bipunctata (Perris) from Saanichton, British Columbia, and Larivière (1992) reported the occurrence of the nabid Himacerus apterous (Fabricius) from the vicinity of Halifax, Nova Scotia.

Asquith and Lattin (1990) recorded the European anthocorid Brachysteles parvicornis (Costa) from New York, and Noodline, New Jersey. Lattin and Asquith (1991) reported additional material of the species from Maine on Picea glauca (Moench) and from Massachusetts on Pinus rigida Mill. With the latter specimens, the oribatid mite Humerobates rostrolamellatus Grandjean was beaten from the trees along with the bug. This is a cosmopolitan mite that occurs on trees and is found in Europe. Pericart (1972), citing Carayon, stated that Brachysteles parvicornis fed upon oribatid mites found on trees. Pericart provided a detailed account of this species of anthocorid in Europe. Little is known of its habits in North America except that it appears to be found on conifers and seems to be associated with the oribatid mite mentioned above. Pericart (1972) reported other hosts in Europe so the bug may be found on non-conifer hosts as well. There is a brachypterous form but, thus far, only fully winged adults have been collected in North America.

Effective management of the interactions within the mite community is critical to biological control of economically damaging phytophagous mites such as Panonychus ulmi Koch (Tetranychidae) (Clements and Harmsen 1990). Although much is known about the potential role of phytoseiid mites in controlling P. ulmi (Dover et al. 1979), mites from at least seven other families may be present in apple orchards (Thistlewood 1991). Stigmaeid mites are predators which may play a beneficial role in biological control in conjunction with phytoseiids (Clements and Harmsen 1992). Eriophyid mites are phytophagous but seldom cause economic damage, and may compete with tetranychids and provide alternative food for predators of tetranychids (Croft and Hoying 1977).

Western flower thrips, Frankliniella occidentalis (Pergande), originally distributed throughout western North America (Bryan and Smith 1956), have since spread to greenhouses in the eastern United States and Canada, and to many other parts of the world (Brodsgaard 1989). Populations have established outdoors in the southeastern United States (Chamberlin et al. 1992) and in several other warm regions of the world (Brodsgaard 1993). but have failed to establish in Ontario (Broadbent and Hunt 1991) and the northern parts of Europe (Brodsgaard 1993). We have not found reports of western flower thrips overwintering outdoors in the northeastern United States.