The European bark beetle, Ips sexdentatus Boerner, carries fungi in puncture pits located on the proximal part of each mandible, the sides of the pronotum, and the elytra.

On the pronotum, each mycangium corresponds to the cup-shaped depression surrounding each seta. Several type III gland cells are associated with each mycangium. The general organization of these cells, commonly found in the epidermis, corresponds to those described by other authors. Their finely granular secretions probably protect the fungi, assure spore adhesion, and also may temporarily inhibit their germination. Similar gland cells were scattered under unspecialized pronotal integument where fungi were not detected.

Thus, it appears that this beetle has evolved a mechanism for the protection or dissemination, or both, of yeasts and fungi such as Ceratocystis sp. This relatively simple system seems to be as efficient as the more evolved mycangia of other species.

Korscheltellus gracilis (Grote) is a pest of red spruce and balsam fir roots in the forests of the northeastern United States and southeastern Canada. The larvae feed below ground on woody and non-woody plant tissues for 2 years before maturing. It was found at 18 localities across New England and Nova Scotia during the summers of 1987 and 1988. On Whiteface Mt., New York, and Mt. Moosilauke, New Hampshire, larvae were absent to uncommon at low (500 m) and high (1300 m) altitudes, but common to abundant in red spruce – balsam fir associations at 700, 900, and 1100 m. During September 1987, larval populations were estimated at 56 000 and 312 000 per hectare in soils at 900 m on Whiteface and Moosilauke, respectively. Dense populations occurred locally, e.g. 27 larvae were recovered from a single 0.25-m2 soil pit at 900 m on Moosilauke. By June 1988, larval numbers on Whiteface and Moosilauke had declined by 51% and 72%, respectively. Seedlings and mature trees of both spruce and fir were damaged by larval feeding on bark and cambium. Seedlings were girdled; mature trees had wounds paralleling the root axes.

Pathogenicity of the microsporidium Nosema fumiferanae (Thomson) in the obliquebanded leafroller, Choristoneura rosaceana (Harris), was evaluated in laboratory bio-assays. When consumed by first-, fourth-, or fifth-instar obliquebanded leafroller larvae, Nosema spores primarily infected the gut and Malpighian tubules. When 2000 spores per square millimetre diet surface were consumed by neonate, fourth-, or fifth-instar larvae, the N. fumiferanae caused 91, 24, and 5% mortality, respectively. Infection by N. fumiferanae had a delayed impact on the older larvae. Large numbers of spores were retained to the adult stage by obliquebanded leafrollers treated as fourth- or fifth-instar larvae.

Relationships among catches of corn earworm moths, Helicoverpa (= Heliothis) zea (Boddie), in pheromone traps, numbers of corn earworm eggs, and corn ears with fresh silks were investigated in eight corn fields during a 2-year period in Brazos River Valley, Texas. Cross-correlation analysis indicated that the catches of corn earworm moths in pheromone traps were closely associated with egg numbers in seven of eight fields with a time differential varying between −1 to +2 days. Cross-correlation peaks for new silks versus eggs occurred with time differentials being mostly positive, indicating that corn earworm egg numbers reached a maximum after corn produced large numbers of fresh silks on ears.

There was a weak but significant linear relationship between egg numbers and corn earworm catches in pheromone traps when corn was in the whorl stage of growth. A stepwise regression model of the form: log (eggs/ha + 1) = 3.71 + 0.22*log(S + 1)*log(T + 1) − 0.3*log(S + 1), where S = numbers of corn ears with new silks per hectare, and T = mean corn earworm moths per trap, explained 52.5% of the variance. These results emphasize the mediating effects of fresh silks on corn earworm oviposition on corn.

Bumble bees rely on stored nectar to maintain high colony temperatures. This study examines some of the costs associated with exhausting stored nectar for a day in confined colonies of Bombus occidentalis Greene and B. melanopygus Nylander. Workers from energy-deprived colonies ceased incubating and allowed brood temperatures to drop to ambient levels. Workers from energy-rich colonies responded to a simulated vertebrate predator by actively moving about and buzzing loudly (apparently searching for the source of disturbance), but those from energy-depleted colonies mostly remained stationary on the comb. Workers from energy-rich colonies responded to an intruding social parasite (a Psithyrus insularis Smith queen) by chasing and attacking it, whereas those from energy-depleted colonies adopted stationary threat postures. In both cases, the more successful defensive strategy of simultaneous attack by several workers was not employed by nectar-depleted colonies. Cooling of final-instar larvae and pupae added to their development times (disproportionately so in the case of pupae), but low temperature per se did not affect their probability of survival. Hence, the costs of short-term energy shortfall include increased susceptibility to predators and parasites and a lengthened period of development. These costs probably relate to energy stores in a nonlinear manner, providing the foundation upon which risk-sensitive foraging decisions can be based.

Enzymes were investigated, by electrophoresis, in a population of Glossina fuscipes fuscipes Newstead collected from Rusinga Island in Lake Victoria, Western Kenya.

The following enzymes were tested: glucose phosphate isomerase, glucose-6-phosphate dehydrogenase (G6PDH), hexokinase. isocitrate dehydrogenase (IDH), malate-dehydrogenase (MDH), phosphoglucomutase, and xanthine dehydrogenase (XDH).

Single monomorphic bands were stained by the following enzymes apparently under the control of single loci: G6PDH, MDH, and XDH. The enzyme IDH showed two bands with very close mobilities and no variation among individuals in the population. Hence IDH was considered as representing a single locus. Glucose phosphate isomerase manifested three alleles and apparently six genotypes. Phosphoglucomutase manifested a double-banded pattern representing an autosomal locus.

Three field tests were conducted in which fresh lodgepole pine (Pinus contorta Douglas var. latifolia Engl.) material, namely bolts with and without bark, bark only, and freshly tapped resin, were placed in beetle-excluding “greenhouse” cages; empty cages served as controls. Two “window” flight traps per cage, at right angles to each other, caught mountain pine beetles (Dendroctonus ponderosae Hopkins) arriving at the cages. Significantly more mountain pine beetles were trapped at cages baited with bolts and wood only than at empty control cages. Primary attraction in the mountain pine beetle is thus established, in the absence of pheromones and normal visual cues (tree stem silhouette). More beetles were trapped at cages baited with bark only and with resin than at empty control cages, but differences were not significant at p = 0.05. The sex ratio of trapped beetles (4.83 females: 1 male) was more than twice as high as the reported sex ratios of free-flying and emerging beetles.

The species composition, diversity, and phenology of a community of water beetles (Dytiscidae) were studied over a 4-year period at George Lake, Alta. There was a pronounced trend of decreasing diversity between years due to the loss of several rarer species. In any year, there were distinct seasonal assemblages of different species, as well as a group of permanent residents. There were few differences in species composition between various microhabitats in the lake. The decline in diversity is attributed to habitat stability and competitive success of one species.

A fungal outbreak of Pandora neoaphidis (Remaudière and Hennebert) Humber (Zygomycetes, Entomophthorales, Entomophthoraceae) caused maximum daily mortality of 6 and 34%, respectively, in sympatric populations of Acyrthosiphon kondoi Shinji and Acyrthosiphon pisum Harris (Homoptera, Aphididae). This epidemic suppressed the A. pisum population but not the A. kondoi population. The results suggest that low level infections in A. kondoi may greatly increase the inoculum available for transmission to the highly susceptible A. pisum.

The efficacies of registered and unregistered foliar sprays against the tuber flea beetle, Epitrix tuberis Gentner, were compared in 1987, 1988, and 1989 at Abbotsford, B.C. Beetles were released serially in treatment plots and visually counted after each release to determine the effectiveness and longevity of residual control. In 1989, emergence cages placed over previously treated plants measured the effect of sprays on the next generation of beetles. Pyrethroids generally resulted in beetle mortality for longer periods of time than did the nonpyrethroids carbaryl, endosulfan, chlorpyrifos, and methamidophos. Several pyrethroids provided residual beetle control for up to 7 days after application. In 1989, bifenthrin, cyfluthrin, cypermethrin, and deltamethrin were as effective in suppressing emergence of the next generation of beetles as was granular phorate applied at seeding. These studies demonstrated that foliar sprays can be a key component of E. tuberis management programs, especially those operating on soil types where the use of granular insecticides is restricted.

Six systemic and two nonsystemic granular insecticides were evaluated by application in the furrow at planting for control of overwintered tuber flea beetles, Epitrix tuberis Gentner. Studies were conducted from 1986 to 1988 in three soil types in the lower Fraser Valley of British Columbia. Of the registered systemic insecticides tested, phorate and aldicarb gave rapid and consistent control of overwintered adults released on the foliage 24–30 days after planting, whereas disulfoton and carbofuran were either less effective or more variable in their control. Terbufos and cloethocarb, not registered for use on potatoes, gave control of adult beetles similar to that of phorate and aldicarb. Mortality of overwintered generation adults resulting from these systemic insecticides was correlated with numbers of beetles emerging in the summer adult generation. Neither fonofos nor chlorpyrifos, the nonsystemic granular insecticides, gave effective control of overwintered flea beetles. Only fonofos significantly reduced the emergence of beetles of the summer generation, but the control was inconsistent between years. When beetles were released on the foliage 56 and 65 days after planting, the fewest beetles emerged from the phorate and terbufos plots. All treatments were less effective in highly organic soils than in mineral soils. The advantages of using granular systemic insecticides for controlling overwintered E. tuberis, and strategies for improving control in association with integrated pest management programs are discussed.

The relationship between temperature and ovarian development rates, as well as the cumulative probability of a female becoming gravid, were determined for the house fly, Musca domestica (L.), based on previously published information. These relationships were combined to form a model that simulates oviposition of house fly populations using average daily temperatures, eggs per cycle, and daily survival as input. Simulation results were compared with observed oviposition in three caged populations of house flies exposed to field temperatures. A high correlation occurred between simulated and observed eggs laid (r = 0.88), as well as between simulated and observed lxmx (r = 0.91). The model overestimated the onset of oviposition for one population, but closely simulated the timing of oviposition for the other two. The model also tended to overestimate the reproductive contribution of flies during the second and subsequent ovarian cycles.

Natural nests of the Africanized honey bee near Tapachula, Chiapas, Mexico, were examined during March and April 1988, approximately 18 months after initial colonization. Most were in hollow trees, but open nests and nests in arboreal termite nests occurred. All nests were less than 6 months old and most less than 2 months. The modal cavity volume was 10–20 L. No brood diseases were seen. Colony density was estimated to be about six per square kilometre, higher than the density of man-kept hives.

Twenty species of Tabanidae in three genera [Hybomitra (15 spp.), Tabanus (four spp.), Haematopota (one sp.)] were caught in Manitoba horse fly traps from mid-May to mid-July in 1987, and from mid-May to mid-August in 1988. Hybomitra lurida (Fallen) and H. nitidifrons nuda (McDunnough) peaked in abundance in late May to early June; H. illota (Osten Sacken) and H. lasiophthalma (Macquart) in early June; H. affinis (Kirby), H. arpadi (Szilady), and H. zonalis (Kirby) in mid-June; H. epistates (Osten Sacken) and H. pechumani Teskey and Thomas in late June to early July. Abundance of H. trepida (McDunnough) peaked twice, in late June and early August. Tabanid density and diversity were greatest during June; few flies were present at the site after mid-July. For most species, at the beginning of the flight season, 80–100% of flies dissected were nulliparous. After approximately 1 month of flight activity, parity in all but three species reached levels approaching 100%, and remained high thereafter. Hybomitra lurida and H. nitidifrons nuda were 100% parous within 2 weeks of their first appearance in traps. Parity of H. trepida increased to 100% after 4 weeks, declined to 40% 2 weeks later, and returned to 100% after another 2 weeks.

Daily patterns of host-seeking activity by female tabanids were determined by hourly trapping (0530–2230 hours) with Manitoba horse fly traps at Seven Sisters, Man., 4 days a week, throughout the summer of 1988. Hybomitra epistates (Osten Sacken) and H. pechumani Teskey and Thomas were most active during late morning or mid-day; H. arpadi (Szilady) and H. zonalis (Kirby) in early afternoon; H. affinis (Kirby), H. illota (O.S.), and H. lasiophthalma (Macquart) in late afternoon; H. nitidifrons nuda (McDunnough) and H. lurida (Fallen) in early evening.

The morning onset of tabanid flight activity usually was related to temperature, but the cessation of activity in the evening was related either to temperature or light, depending on which was first to fall below threshold levels. Tabanid flight activity was generally low at temperatures below 20°C, although H. lasiophthalma and H. affinis occasionally were caught at 12°C. Little flight activity occurred at light intensity levels below 1000 lx regardless of temperature. At Churchill, Man., where tabanids were trapped hourly from 27 July to 15 August in 1988, H. affinis and H. frontalis (Walker) activity was low below 14°C, although some activity occurred at 6°C.

A spruce budmoth population reduction of 82%, as measured by moth emergence, was realized after a foliar spray in which Futura®, a commercial Bacillus thuringiensis Berliner (B.t.) formulation, was added to a suspension of Steinernema carpocapsae (Weiser). The nematode suspension, which took advantage of the wetting and spreading agents in the formulation, was applied to runoff at the rate of 9785 viable infective juvenile nematodes per litre. Mortality was attributed to the nematodes; B.t. was not available to the cryptic larvae. Soil drench treatments were encouraging, and suggested that applications of nematodes to the soil may be feasible.

Combinations of Bacillus thuringiensis Berliner subspecies kurstaki and Beauveria bassiana (Balsamo) Vuillimen formulated on granules were applied separately and in combination to field corn to suppress larval populations of the European corn borer, Ostrinia nubilalis (Hübner). Research was conducted in 2 separate years. Laboratory-reared O. nubilalis eggs or larvae were placed on the plant during either the whorl stage (V6) or the pollen-shedding stage (R1) to simulate first- and second-generation O. nubilalis oviposition periods, respectively. Efficacy was determined by measuring the length of European corn borer tunnels in the corn stalk at harvest time. In the 1st year, first generation, and second generation (of 2nd year) B. thuringiensis and B. bassiana alone and in combination caused significant reductions in tunneling compared with that in the check populations. There were no significant differences in tunneling between any treatments in the second-generation study of year 1. Bacillus thuringiensis and B. bassiana were independent of each other in their suppression of insects. Tunneling by the naturally occurring second-generation larvae (year 2) was recorded to determine if B. thuringiensis and B. bassiana applied in the V6 stage persisted in the plant. Pith samples were excised from nodal plates 7–10 of the corn stalk to determine the incidence of B. bassiana. There was a significant correlation (r = −0.376) (P≤0.05) between the occurrence of B. bassiana in the corn plant and tunneling by second-generation larvae. These data indicate that B. bassiana placed in the whorl of the corn plant may provide season-long suppression of O. nubilalis.

Allozyme and morphological variation were investigated for mountain pine beetle populations in limber pine and lodgepole pine in Alberta and British Columbia. Fourteen gene loci, five of which were polymorphic, were studied. Heterozygote deficiencies were detected at the ME locus for 13 of the 16 groups of beetles sampled. Selection against heterozygotes appears to be the most plausible explanation. There was no significant difference in heterozygosity between beetles from lodgepole pine and those from limber pine. Relatively high levels of genetic differentiation, in terms of allele frequency, were observed among beetles from different sites, host species, seasons, and individual conspecific trees within a site. Low levels of differentiation were observed between beetle generations at a site and between sexes. We attribute significant host-associated genetic differentiation to differential survival in hosts rather than to differential host preference of beetle genotypes. Standardized discriminant function analysis of 12 morphological characters indicated significant differences in beetle shape between sexes, host species, and among sites. Overall, there was little evidence of preferential host selection by beetles which would imply substructuring of Dendroctonus ponderosae Hopkins populations along host lines.

Agapeta zoegana L. (Lepidoptera: Cochylidae) is a Eurasian root-mining moth introduced into North America for control of spotted knapweed, Centaurea maculosa Larnarck. The biology and host specificity of the moth were described by Müller et al. (1988, 1989). Early-instar larvae mine the epidermal tissues of the root crown. Older larvae mine the root cortex and endodermis and cause considerable damage, especially to small plants or when several larvae infest a single large plant. Larvae can migrate below ground to a new host plant if the initial knapweed plant has been destroyed. The moth overwinters as a larva in the root and emerges as an adult in June through August. Several generations per year may occur.

First detection of the Russian wheat aphid, Diuraphis noxia (Mordvilko), in the United States occurred in March 1986 in the Texas panhandle. Within 3 years, this aphid pest was found in 15 western states and three provinces in Canada. Each year since 1986, Russian wheat aphid has been responsible for millions of dollars in grain loss and insecticide treatment costs (Anonymous 1988, 1989). Physiological responses of the plants to the aphid include chlorotic streaking, rolled leaves, entrapment of developing seedheads, stunting, reduced tiller production, and reduced yields (Hewitt et al. 1984; Johnson et al. 1988; unpublished data).