An evolutionary model was constructed for the white pine weevil (Pissodes strobi Peck). This weevil attacks Sitka spruce [Picea sitchensis (Bongard) Carriere], and Sitka spruce trees have two forms, one being susceptible to the insect attacks and the other being resistant to attack. There is a fear that insects may develop tolerance to the resistant trees. The strategy of interplanting susceptible and resistant trees to minimize the likelihood of the insects developing tolerance mechanisms to circumvent the resistance is examined. It is found that if only one gene locus is involved, the development of tolerance occurs more quickly than if resistance is governed by two independent loci. The rate of evolution of tolerance to tree resistance is retarded by increased adult survivorship, the degree of recessiveness of the gene, preferential attack of susceptible trees, redistribution of intolerant insects from resistant to susceptible trees, and the immigration of wild-type insects.

We here give Echinocoleus new ranking as a subgenus of Ptomaphagus. Ptomaphagus (Echinocoleus) acutus sp.nov. is described from the southeastern United States (Alabama, Georgia, Florida). It is the most plesiotypic member of a group in which all other species live in the western United States and (probably) adjacent Mexico. All are myrmecophilous with Pogonomyrmex and Aphaenogaster (= Novomessor) harvester ants. A phylogenetic analysis is given for the subgenus. The main synapomorphies of Echinocoleus, which are mostly interrelated with myrmecophily, are reduction of body length and broadening of elytra, reduction of antennal length, verticalization of mesocoxal insertion, reduction of mesosternal carina, body with a golden pubescense, and a pointed projection at the end of the spermatheca.

From 1985 through 1995, burlap flaps were stapled to 100 trees in a 10 by 10 grid in a 4-ha forest plot. Each year, the number of fourth- to six-instar larvae of gypsy moth, Lymantria dispar L., under each burlap flap was recorded at least weekly in June and into July. From 1987 through 1990,100 000–120 000 hatching gypsy moth larvae were released near the center of this plot in early May at the time of natural hatch. In the 4 years that releases occurred, there was a distinct, single cluster of large larvae under the burlap flaps near the center of the plot. This pattern did not occur in other years. Results are interpreted to mean that total dispersal of larvae from first to ultimate instar is limited, even though first instars are readily dispersed by wind.

An extract from seeds of the neem tree, Azadirachta indica A. Juss, enriched with azadirachtin, was evaluated in three experiments for control of the spruce aphid, Elatobium abietinum (Walker), on potted spruce trees in a greenhouse. The extract in Exps. 1 and 2 was first applied in February 1993 when spruce aphid populations were initially low; populations were observed weekly for 15 weeks. In Exp. 1, foliar applications to the runoff point of 150 ppm azadirachtin applied three times (biweekly) held populations below 5.3 aphids per 6-cm twig samples; populations on trees treated at 75 ppm, or with emulsifier only, reached 32.2 and 26.9 aphids per sample, respectively. With five weekly applications (Exp. 2), suppression to < 14 aphids per sample was achieved with both 150- and 75-ppm treatments; populations on control trees peaked at 36.8 aphids per sample. The extract at 150 ppm in Exp. 3 significantly reduced the number of aphids on trees that initially had high populations. The results indicate that neem has potential for operational use against aphids in conifer seed orchards.

The nine species of the endemic North American Agabus seriatus-group are revised. All species occur west of the Rocky Mountains with A. lugens LeConte also occurring on the Great Plains and A. seriatus (Say) transcontinental in mid-latitudes. The species are placed in four subgroups, namely the seriates-subgroup with A. seriatus, A. lugens, and A. perplexus Sharp; the brevicollis-subgroup with A. brevicollis LeConte, A. pandurus Leech, and A. roguus new species; the ilybiiformis-subgroup with the single species A. ilybiiformis Zimmermann; and the regularis-subgroup with A. regularis LeConte and A. minnesotensis Wallis. Geographical variation in A. seriatus is analyzed and it is concluded that recognition of subspecies of A. seriatus is not warranted and A. s. intersectus (Crotch), NEW SYNONYMY, is relegated to a synonym of A. seriatus. For each species the following is provided: synonymy; description and illustration of taxonomically useful characters; notes on relationships, variation, distribution, and ecology; and a map of collection localities. A key to species is provided and lectotypes designated for A. brevicollis LeConte, A. lugens LeConte, A. perplexus Sharp, Gaurodytes suturalis Crotch (= A. lugens), and Ilybius regularis LeConte.

Diplolepis nodulosa (Beutenmüller) induces small, monothalamous, prosoplasmic galls in stem tissues of Rosa blanda Aiton. Adults and galls are redescribed and notes on distribution, host records, morphological variation, and a comparison with related species are presented. Galls are commonly attacked by the inquiline Periclistus pirata (Osten Sacken). Data on life history and mortality of inducers and inquilines, along with seasonal variation in gall density, were obtained from a study site near Sudbury. Ontario, in 1993 and 1994. Inquilines killed 55% of the inducer population in 1993 and 65% in 1994. The abundance and density of galls fluctuated over the 2 years; however, the proportion of galls modified by inquilines remained constant. Six species of parasitoids caused an additional 17% inducer mortality. Aprostocetus sp. was the dominant parasitoid of D. nodulosa, whereas the other five species were incidental. The assemblage of parasitoids associated with galls modified by P. pirata caused 13% inquiline mortality and include seven species, of which Eurytoma spp. and Caenacis sp. were dominant. The unique aspects of the D. nodulosa gall system are discussed.

The commercial feeding stimulant Pheast® was tested in the laboratory to determine its attractive and phagostimulatory effects on larval Choristoneura rosaceana (Harris). In choice experiments, larvae were attracted initially to filter paper discs treated with Pheast, but did not remain on or near treated discs. Larvae were not attracted initially to raspberry leaf discs treated with Pheast, but were more likely to stay near treated leaf discs than water-dipped ones. Larvae were neither attracted to nor arrested on whole raspberry leaves treated with Pheast. In no-choice experiments, larvae fed Pheast-treated leaves consumed more leaf tissue than, and grew almost twice as quickly as, larvae fed leaves dipped in water. When larvae were fed leaves treated with Dipel WP (Bacillus thuringiensis var. kurstaki) plus 5% Pheast, the mortality was 93% greater than that of larvae fed leaves treated with Dipel WP alone. These results suggest that Pheast has potential to enhance efficacy of B. thuringiensis against C. rosaceana on raspberries in the field.

The wide distribution of obligate thelytoky in oribatid mites (Acari: Oribatida) raises the question of the mechanisms that allowed genetic diversity to be maintained or even promoted in these taxa. We tested whether or not endosymbiotic bacteria Wolbachia are associated with thelytoky in eight species of oribatid mites (as it is for most thelytokous parasitic Hymenoptera studied so far) by using a polymerase chain reaction assay. Our negative results in the selective amplification of Wolbachia DNA suggest that these bacteria are not responsible for the thelytokous mode of reproduction of oribatid mites. On the basis of known or suspected cytogenetic mechanisms in oribatid mites (automictic thelytoky, inverted meiosis), we discuss an alternative hypothesis for the inducement of thelytoky, and its relevance to the observed diversification of thelytokous oribatid mites over evolutionary time.

Resistance was documented in 1995 to commonly used organophosphorus, carbamate, and pyrethroid insecticides in populations of western flower thrips, Frankliniella occidentalis (Pergande), from six commercial greenhouses in Ontario. Adult female thrips were placed in glass vials treated with technical-grade insecticides and mortality at 18 h was compared with a single discriminating concentration, the computed LC99 of a reference laboratory population. Baseline dose–response regressions for insecticides commonly used in Ontario greenhouses were obtained for the laboratory population of western flower thrips. The organophosphorus compounds chlorpyrifos and malathion and the carbamates methomyl and bendiocarb were the most toxic materials tested; whereas the pyrethroid deltamethrin and a phosphoroamidate acephate were the least toxic. The addition of piperonyl butoxide to solutions of deltamethrin was highly synergistic. The mixture of deltamethrin and endosulfan (1:1) was moderately synergistic. Populations of western flower thrips from commercial greenhouses were resistant to deltamethrin, but deltamethrin mixed with piperonyl butoxide or endosulfan was synergistic in all cases. None of the populations were resistant to all of the insecticides tested. Recommendations are presented for the development of a resistance-management strategy for western flower thrips.

Two new species of Diapheromera, D. kevani and D. petita, are described from Mexico, the first record of these species and of the genus from Baja California. They were found while studying the stick insects (Phasmatoptera) of the Baja California Peninsula.

The oribatid fauna of commercial balsam fir [Abies balsamea (L.)] forests of western Newfoundland were surveyed through Berlese funnel extraction of samples taken from soil and various forest microhabitats. A total of 83 species or species complexes representing 39 families was collected. Fourteen genera and 36 species are new records for Newfoundland. One genus, Haplozetes Willmann, 1935, is a new record for Canada. For each species, notes on abundance in soil samples and distribution among microhabitats are provided and for the more abundant species, seasonal variation in abundance of immature and adult stages is plotted.

Eight species are recognized within the New World fauna of the tribe Pogonini: Thalassotrechus barbarae (Horn, 1892), Ochtozetus bicolor (Brullé, 1843), Ochtozetus inexspectatus sp.nov. (type locality: Santa Isabel, Mato Grosso, Brazil), Diplochaetus rutilus (Chevrolat, 1863), Diplochaetus megacephalus sp.nov. (type locality: Bottomless Lakes State Park, New Mexico), Diplochaetus emaciatus Bates, 1891, Diplochaetus planatus (Horn, 1876) [new combination] and Pogonus texanus Chaudoir, 1868. Two names are listed for the first time in synonymy: Pogonus parallelus LeConte, 1874 (= Pogonus lecontei Horn, 1876) with Diplochaetus rutilus (Chevrolat, 1863) and Diplochaetus desertus Van Dyke, 1953 with Diplochaetus emaciatus (Bates, 1891). Lectotypes are selected for Trechus barbarae Horn, 1892, Pogonus emaciatus Bates, 1891 and Pogonus depressus LeConte, 1874. A key to the species, illustrations of the most important characters and distributional maps of most species are included.

During a study on the importance of spiders as predators of the cabbage butterfly Artogeia rapae L. (Lepidoptera: Pieridae) in cultivated cruciferous fields in Quebec, 209 specimens (114 were immatures riding on the back of a female) of Trochosa ruricola (DeGeer) (Lycosidae), 21 specimens of Ostearius melanopygius (O. Pickard-Cambridge) (Linyphiidae), and one specimen of Dictyna decaprini Kaston (Dictynidae) were found by pitfall traps and aspirator at L'Acadie, Quebec (45°20'N, 73°20'W) in cabbage, Brussels sprouts, and broccoli plots. This is the first record of these species in Canada.

Cyphocleonus achates (Fahaeus) is a Eurasian, root-feeding weevil introduced into North America for the biological control of spotted knapweed, Centaurea maculosa Lamarck. Stinson et al. (1994) reported that C. achates is one of the most damaging root-feeding insects on knapweed in Eurasia and should be a valuable addition to the biocontrol effort in North America. The biology, host specificity, and potential impact of the weevil were described by Stinson et al. (1994). Larvae mine into the root cortex where they induce formation of a conspicuous root gall. Feeding by older larvae causes much damage, especially to small plants or plants containing several larvae. The weevil overwinters as a larva in the root and emerges as an adult from mid-July to October. Adult weevils are large (14 mm long) and flightless, and feed on knapweed foliage. The weevil has one generation per year.

The efficacy of two production batches of conidia of Beauveria bassiana (Balsamo) Vuillemin that showed differential field efficacy in 1992 (GHA 92) and 1994 (GHA 94) were compared against grasshoppers in the laboratory and field. Conidia of GHA 92 and GHA 94 exhibited good germination (> 92%) by 24 h, but the rate of germination was slower for GHA 94 than for GHA 92. Although both conidial batches were highly virulent (LD50 < 6 × 103 conidia per nymph) against nymphs of Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae) in the laboratory, GHA 92 was slightly more virulent than GHA 94. Conidia were applied to field populations of grasshoppers in a 1.5% emulsifiable oil-emulsion amended with 4% clay at a volume of 112 L/ha. There were no differences between GHA 92 and GHA 94 in the deposition of spray droplets on water-sensitive papers or of conidia on leaves and coverslips (2.4 × 10 to 4.1 × 10 cfu/cm2). All grasshopper nymphs collected from plots sprayed with conidia of GHA 92 and GHA 94 were equally infested with B. bassiana; conidial populations averaged 3.5 × 103 to 4.3 × 103 cfu/nymph. Conditions were hot, dry, and sunny, and regardless of the batch, persistence of conidia was equally short on both leaves and grasshoppers. Neither treatment of B. bassiana significantly reduced field populations nor did either impact differentially on specific grasshopper taxa. However, among grasshoppers collected immediately after conidial application and maintained in cages in the greenhouse, over 80% died of infection with B. bassiana. For both conidial treatments, the prevalence of disease in caged grasshoppers decreased with the sampling date but the onset of mycosis always occurred 3–4 days after collection. This study indicates that environmental conditions in the field and not pathogen virulence or targeting were responsible for the poor efficacy of B. bassiana against grasshoppers.

Although Amphiagrion abbreviatum (Selys) and Argia vivida Hagen often occur at the same geothermally heated springs in western Canada and the United States, they differ markedly in their abundance at any particular site. There is no relationship between crude data on water temperature, conductivity, or aquatic vegetation and the relative abundance of the two species, but there is a striking correlation with presence or absence of trees. The absence of A. abbreviatum from heavily treed areas is associated with the paucity of suitable daytime perching sites, and there may be competitive pressure exerted by A. vivida for the perching sites that are available. Argia vivida does not live at open sites because it requires trees for night-time roosts. Argia vivida roosted higher than A. abbreviatum in cages and held the body at a greater angle from the cage wall. The roosting posture of A. vivida is probably related to interception of solar radiation in the morning, and the body positions of both species possibly provide defence against predation.

In a laboratory experiment on the decision rule underlying the avoidance of flower revisitation by foraging bumble bees (Bombus impatiens), artificial flowers were arranged in two rows. For each flower visited, the choice was either to travel straight ahead onto a flower in the same row or to change direction and choose a flower in the other row. The distance between rows was manipulated to be smaller than, equal to, or greater than the distance between flowers in the same row. When the distances between adjacent flowers within a row and between rows were equal, a significant tendency to travel straight ahead was observed. This tendency was sensitive to changes in distance between rows, even when the distances between rows far exceeded the distance between flowers within a row. The tendency was abolished when the distance between rows was smaller than the distance between flowers within a row. A significant alternation of the bumble bee between rows (zigzag path) was observed in only one condition: when not only the distance between rows was much smaller than the distance between flowers in the same row, but also when the rows were staggered such that the bee could alternate between rows while still travelling in an almost straight line. These results show that the two variables of distance and angle are integrated, and that the choices made by bumble bees do not reflect a simple rule. Future research on tradeoffs is suggested.

In two-choice laboratory feeding trials in Petri dishes, adult carabid beetles, Pterostichus corvus (Leconte) and Pterostichus femoralis (Kirby), ate a higher percentage of grasshopper eggs, Melanoplus bivittatus (Say), than of cat food. Pterostichus corvus ate more eggs than did P. femoralis. Grasshopper eggs buried in soil in terraria were eaten by P. corvus adults at more than twice the rate of eggs exposed on the soil surface; predation rates at depths of 2.5 and 5 cm were the same. In plant-propagation trays, predation by P. corvus of buried grasshopper eggs was studied under three types of ground cover: Nicotiana seedlings, with rosette-form growth habit; barley seedlings, which exhibited upright growth; and bare ground. A significantly higher percentage of eggs was eaten under the Nicotiana than beneath the other types of ground cover, and predation rates did not differ between the barley and bare-ground treatments. Pterostichus corvus appears to be a suitable candidate for enhancement of natural biological control of grasshopper eggs, and manipulation of vegetation cover in grasshopper egg beds may be an effective technique for enhancing predation rates.

The carrot weevil, Listronotus oregonensis (LeConte), was monitored at 11 research or commercial carrot plantings at Holland Marsh, Kettleby, Ontario, using three methods, i.e. wooden plate (Boivin) traps to capture adults, carrot root sections placed in the soil to detect oviposition, and recording the numbers of adults present on carrot root sections. All three methods provided similar records of the seasonal pattern of adult activity. At most sites, thresholds used to determine the need for insecticide applications were reached or exceeded soon after the beginning of monitoring.

There were significant linear relationships among the seasonal activity parameters generated by the three methods and between those parameters and percentage injury at harvest. Control programs that would have resulted from the use of each method are discussed.

A redescription of Myzocallis (Lineomyzocallis) melanocera Boudreaux & Tissot is given, and Myzocallis (Lineomyzocallis) neoborealis sp.nov. and Myzocallis (Lineomyzocallis) atropunctatus sp.nov. are described. Lectotypes for M. (L.) melanocera and Myzocallis (Lineomyzocallis) walshii (Monell) were designated. Myzocallis (Lineomyzocallis) occultas Richards is declared a new synonym of M. (L.) walshii. The taxonomic affinities of these aphids are discussed.