Carabid beetles were collected using pitfall traps and tree bands in forest stands in southwestern Pennsylvania subjected to defoliation by gypsy moth for the first time. Some of the stands were treated aerially with Bacillus thuringiensis Berliner (B.t.). The guts of all carabids collected were tested for the presence of gypsy moth proteins using the ELISA technique. Twenty-seven of the 33 species (82%) collected from pitfall traps, and four of the seven species (57%) collected under tree bands, tested positive. Of the 1142 individuals from pitfall traps and 73 individuals from tree bands, the percentages positive were 45 and 38%, respectively. Calosoma frigidum Kirby had the highest percentage positive (78%) of any species. Statistically significant differences in percentages positive between B.t.-treated and untreated plots were found only for Pterostichus mutus Say and P. coracinus Newm., and when all species were combined. The presence of nucleopolyhedrosis virus in the gypsy moth population was unanticipated and may have influenced these results through increased feeding on carrion.

The Nearctic species of the subgenus Anomophagus Reitter of the genus Rhizophagus Herbst are revised. Four taxa are recognized: R. brunneus brunneus Horn 1879, R. brunneus fenyesi Méquignon 1913a, R. pseudobrunneus sp.nov., and R. galbus sp.nov.

For the other Nearctic species of the genus, a diagnosis, a type material section, and distributional notes are provided. Two new taxa are described, R. minutus rotundicollis and R. pusillus. Seven specific names are treated as new junior synonyms, namely (with the valid name in parentheses): R. longiceps Casey 1916 and R. rectus Casey 1916 (= R. cylindricus LeConte 1866); R. minutus quadriguttatus Méquignon 1913b (= R. minutus minutus Mmnerheim 1853); R. remotus luteus Méquignon 1913b (= R. remotus LeConte 1866); R. sculpturatus horni Méquignon 1913b (= R. sculpturatus Mannerheim 1852); R. dimidiatus testaceus Méquignon 1913b and R. dimidiatus assimilis Méquignon 1913b (= R. dimidiatus Mannerheim 1843). The subgenera name Syringobidia Casey 1916 (type species: R. cylindricus LeConte 1866) is treated as a new junior subjective synonym of Rhizophagus s.str. A key to all Nearctic species of Rhizophagus is provided with distribution maps of the species.

We propose a sequential sampling plan for adult tuber flea beetles, Epitrix tuberis Gent., in potato fields, which is based on a confidence interval calculated around a critical density value (Iwao 1975) and which uses Taylor’s Power Law (Taylor 1961) to estimate the variance. Because of the highly edge-biased gradients of density displayed by this insect, separate sequential expressions have been calculated for densities at the edges and centers of fields.

In a survey of 12 commercial potato fields, spring-generation E. tuberis densities in centers of fields were always far below the threshold level of one beetle per 10 plants employed at the time of sampling. The survey also indicated that fields that have been sown with potatoes for 2 consecutive years have higher beetle densities than fields sown with potatoes for a 1st year. Edge:center density ratios, however, were the same for the two categories of fields.

The solitary aphid parasitoid Ephedrus californicus Baker is able to discriminate between unparasitized and parasitized third-instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris). Superparasitism varied with the number of mature eggs (which is age-dependent) present in the ovaries as well as with the number and the quality of any hosts encountered. Conspecific superparasitism varied with wasp age; older females, with a large egg supply, accepted hosts parasitized by a conspecific female if unparasitized aphids were unavailable. Self superparasitism occurred at all ages; it was the least likely behaviour compared with egg deposition in unparasitized and conspecific-parasitized hosts. Prior experience (learning) was not necessary for host discrimination, but it did influence the search rate, which was higher in inexperienced than experienced females. In choice experiments, wasps preferred conspecific- over self-parasitized aphids and thus were able to distinguish between them. It is suggested that oviposition markers vary among conspecific females. The data are discussed with reference to theories about oviposition decisions and progeny allocation in solitary hymenopteran parasitoids.

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), the major hydroxamic acid present in corn root, was studied for its effects on western corn rootworm, Diabrotica virgifera virgifera (LeConte). Exogenously applied DIMBOA caused mortality in western corn rootworm larvae feeding on fresh corn roots. The LC50 (lethal concentration for 50% mortality) value (fiducial limits) was 153 ppm (108–209) and the LC90 value was 917 ppm (560–2297). The deleterious effects of DIMBOA on western corn rootworm larvae possibly are due to both feeding deterrence and toxicity. In a replicated pot trial during two growing seasons, two corn lines developed by Agriculture Canada from CIMMYT collections, ITR 3872 with high DIMBOA content in roots, and NTR-2 Ger. 4042 with low DIMBOA content in roots, were evaluated for resistance to western corn rootworm larvae. The results indicated that the high DIMBOA line (but not the low DIMBOA line) stressed western corn rootworm larvae to produce inferior adults based on the measurement of adult emergence number, adult weight, and adult head-capsule width. The effect of western corn rootworm on both corn lines with different DIMBOA levels was measured based on plant growth parameters including plant height, stem thickness, plant fresh weight, root fresh weight, plant dry weight, and root dry weight. ITR 3872 (high DIMBOA) showed significantly less damage than NTR-2 Ger. 4042 (low DIMBOA) in almost all plant parameters measured. The results suggest that DIMBOA may in some instances contribute to the resistance of corn to western corn rootworm larvae.

A soil-dwelling predatory mite, Geolaelaps sp. nr. aculeifer (Canestrini), introduced inundatively at a rate of 6000 mites per plant to the sawdust substrate of hydroponically grown, greenhouse cucumbers significantly reduced numbers of fungus gnat, Bradysia spp., larvae and adults over a 10-week period. Inundative introductions of 1600 mites per plant reduced emergence of western flower thrips, Frankliniella occidentalis (Pergande), adults to about 30% of that in the controls over a 40-day trial. An inoculative introduction of 125 mites per plant to cucumber plants in selected rows in a commercial greenhouse reduced peak fungus gnat numbers to about 20% of those in untreated rows. These results suggest that a single inoculative introduction of Geolaelaps sp. nr. aculeifer, early in the crop cycle, would maintain control of fungus gnat populations in greenhouse cucumber crops at an acceptable level. This predator would also contribute to biological control of western flower thrips by reducing emergence of adults.

Centroptilum infrequens McDunnough, 1924 was found to be widespread in Canada and was described in detail at the 5th International Ephemeroptera Conference, Marysville, Australia, 1987 (Lowen and Flannagan 1989). At that time, similarities between C. infrequens and published accounts of Pseudocentroptilum pennulatum (Eaton 1870) were noted and it was suggested that these species are conspecific. We have recently compared specimens of C. infrequens with specimens of P. pennulatum from western Europe, and have noted no discernable differences at any life stage. We therefore conclude that Centroptilum infrequens McDumough, 1924 is a junior synonym of Pseudocentroptilum pennulatum (Eaton) 1870. This is the first record of Pseudocentroptilum in North America and the first record of a holarctic Pseudocentroptilum species, as P. pennulatum is also known from the arctic Ural and Pacific Coast regions of the Soviet Union.

Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), were found on the underside of needles of western hemlock, Tsuga heterophylla (Raf.) Sarg., with higher densities in the mid-crown area toward the outer tips of branches. Fringe and dominant trees were preferred oviposition sites over trees in lower crown classes or shaded positions. Vertical differences in needle density were considerable and led to high variability in insect densities when expressed on a per branch basis. When densities of eggs were based on a fresh branch weight basis there was a significant decrease in sample bias caused by the uneven distribution of foliage over the crowns.

A systematic analysis of larvae of 11 Nearctic species of Hygrotus Stephens was undertaken. The larvae are described and characterized; a key for their discrimination and illustrations of structural features of representatives of first- and third-instar larvae are provided. Many structural features, especially detailed variations in the chaetotaxy of cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi, were found to be useful for systematic and phylogenetic comparisons. Based on 21 larval characters, a cladistic analysis of the species studied was developed. A sister-group relationship between H. laccophilinus (LeConte) and the remaining available species is suggested. The less derived species, i.e. those without natatory setae on the legs, appear phylogenetically more closely related to the larvae of Hydroporus s.str. Hygrotus masculinus (Crotch) is the most derived species of the genus and, for many characters, seems more closely related to Hyphydrini. According to larval morphology, it is hypothesized that the genus Hygrotus diverged posteriorly to the genus Hydroporus Clairville.

Exposure of adult rusty grain beetles, Cryptolestes ferrugineus (Stephens), saw-toothed grain beetles, Oryzaephilus surinamensis (L.), and red flour beetles, Tribolium castaneum (Herbst), to filter papers treated with the organophosphorus insecticides malathion or chlorpyrifos-methyl often affected offspring production in survivors. Groups of five male and five female survivors were placed on ground wheat at 30°C and C. ferrugineus and O. surinamensis adults produced fewer offspring with prolonged exposure to chlorpyrifos-methyl; malathion had no effect. Tribolium castaneum adults produced significantly more offspring with increasing exposure to both malathion and chlorpyrifos-methyl indicating stimulation of oviposition or a selection for increased fitness in survivors.

Females of the solitary parasitoid Aphelinus asychis Walker discriminated between unparasitized and parasitized second-instar nymphs of the pea aphid, Acyrthosiphon pisum (Harris). Wasps normally avoided superparasitism, except when they were confined with few hosts for a long time. Parasitoid females did not need previous experience with unparasitized aphids (learning) in order to discriminate. They probed with the ovipositor any aphids encountered, a behaviour suggesting that host acceptance and rejection were determined by internal cues. Prolonged ovipositor insertion (>80 s) was correlated with host acceptance and egg deposition, but short insertion times (≤80 s) generally indicated host rejection. Females tended to reject both self- and conspecific-parasitized aphids when provided with two of each kind. We consider hypotheses mat conspecific superparasitism may be adaptive and give examples to show exceptions. We propose that, in egg-limited parasitoid species such as A. asychis, a reproductive strategy based on the regulation of egg production and on oosorption can explain the equal avoidance of self and conspecific superparasitism.

A two by two factorial experiment in a randomized complete block design tested single and combined effects of tree felling and semiochemical baiting on the attractiveness of spruce (Picea spp.) trees treated with monosodium methanearsenate (MSMA) to Dendroctonus rufipennis (Kirby) in British Columbia and Alaska. In British Columbia, tree felling and semiochemical baiting had significant effects on attack density, but in Alaska only tree felling had a significant effect. Semiochemical baiting had a significant effect on within-tree attack distribution in British Columbia but cot in Alaska, regardless of the felling treatment. The felled treatment captured more beetles than the not-felled treatment regardless of the baiting treatment in British Columbia, but only in the absence of a semiochemical bait in Alaska. The differences between the two locations may have been caused by lower temperatures and beetle population density in Alaska. Effective spruce beetle management with MSMA-treated trees requires tree felling, and beetle capture can be improved with the use of a semiochemical bait.

A comparison of the effects of infestation by known numbers of pea aphids, Acyrthosiphon pisum (Harris), on six field pea cultivars was made in field cage tests. The largest population of aphids developed on the cultivar Trapper and the smallest on the cultivar Century, with differences in aphid numbers between these cultivars significant for mature plants. Infested plants of Trapper had a significantly lower number of pods per plant, and infested plants of all cultivars had decreased seed weights, both per metre row and of 250 seeds, when compared with control plants. In all cultivars except Trapper, the most severely affected yield component was weight of 250 seeds.

Eggs of western blackheaded budworm, Acleris gloverana (Walsingham), are laid on the lower surface of western hemlock, Tsuga heterophylla (Raf.) Sarg., needles. A comparison was made of the following measures of sample branch size as a basis for expressing egg density: fresh branch weight, branch area, total twig length, branch volume, and number of buds. The criteria for selection of these measures were as follows: correlations of branch size with dry needle weight, variances of egg density and their relative contribution to sample size, and ease of measurement. Fresh branch weight was the best choice. A sequential sampling system was developed on this basis and was related to a scale of predicted defoliation. In addition, a transformation was provided for use in data analysis.

The Colorado potato beetle is a major worldwide pest of potato and several other solanaceous plants. Insecticidal resistance is a serious problem in the northeastern and mid-Atlantic regions of the United States and a developing problem in other potato production areas of the United States and Canada (Forgash 1985; Johnson and Sandvol 1986; Boiteau et al. 1987). In the northwestern United States, insecticides applied to control the green peach aphid also control Colorado potato beetle, but these insecticides are likely to become ineffective due to the development of resistance or unavailable because of restricted use and environmental concerns. Biologically based management strategies are needed to reduce dependency on insecticides; these strategies require new basic knowledge including understanding prolonged diapause in populations of the Colorado potato beetle. Krysan et al. (1986) established that the occurrence of prolonged or repeated diapause can influence management strategies for insects, especially with respect to crop rotation.

Four different types of insect viruses have been isolated from the eastern spruce budworm, Choristoneura fumiferana (Clem.), but most research efforts have been concentrated on developing the nuclear polyhedrosis virus (NPV) as a viable control agent (Cunningham 1985). There are no published reports of LD50 values for this important forest pest. Recently, a LC50 of 483 viral polyhedra per square millimetre of diet surface for fifth-instar budworm larvae was determined using surface contamination feeding techniques (Cunningham et al. 1983). Because the dosages used in efficacy trials are derived from laboratory LD50 values, experiments were conducted to determine the virulence of this NPV to eastern spruce budworm. Bioassays were conducted with all feeding instars. Reported here are values for the LD50 dosages for third-, fourth-, fifth-, and sixth-instar spruce budworm larvae.

Promoresia elegans (LeConte), Optioservus fastiditus (LeConte), and Stenelmis nr. bicarinata LeConte coexist in Duffin Creek, Ont., making up 3.78–23.92% of the riffle fauna present.

Promoresia elegans and O. fastiditus appeared to have semi-voltine life histories. Stenelmis nr. bicarinata appeared to be univoltine but with overlapping generations and slow recruitment occurring from late summer to fall; growth was slow in winter but fast in spring and summer.

Based on the index of relative importance (Pinkas et al. 1971), detritus was identified as the most important food source for all size classes and all species throughout the year. Microinorganics ranked second, with diatoms, fungal hyphae, and vascular plant material being the least important food sources. There was no indication of ontogenic food switching in any of the species.

The Schoener (1970) niche overlap index indicated almost complete dietary overlap (Cxy = 0.78–0.97) among the three species throughout the year and the Hurlbert (1978) niche overlap index similarly indicated a convergence of diets (L = 1.31–3.54).

Niche breadth values were found to be high for all species on the rock surfaces (generalist diet) but were lower in the hyporheic zone indicating a higher degree of specialization there.

The alfalfa leafcutting bee, Megachile rotundata (Fab.), is an important pollinator of alfalfa in western Canada and is widely utilized for alfalfa seed production (Richards 1984). As a beneficial insect, the alfalfa leafcutting bee must be considered, along with the honey bee, Apis mellifera L., as a non-target organism of importance in evaluations of potential microbial control agents for use against major insect pest species on the Canadian prairies.

Pea aphids, Acyrthosiphon pisum (Harris), were sampled weekly or biweekly over the summers of 1985 and 1986 in a total of 15 commercial plantings of Century, Trapper, or Triumph field peas across Manitoba. Pea aphid populations rose more quickly in fields of Trapper than in Century or Triumph fields. The owners of all Trapper fields sampled initiated aerial application of insecticide for pea aphid control; at the time of spraying in 1985, plants in Trapper fields had significantly greater numbers of aphids in sweep samples than such samples from Century or Triumph fields. In 1986, Triumph plants supported greater numbers of aphids than Century or Trapper plants. Triumph plants remained green longer than plants of the other cultivais; in 1985 pea aphid numbers on this cultivar were highest on the last date sampled.

Yield components were measured in sprayed and unsprayed plots within the commercial fields. When data were averaged for each cultivar, there were no significant differences in yield per area or in 1000 seed weight between sprayed and unsprayed plots. Data indicated that existing economic thresholds are too low for Trapper peas. However, one of the fields of Trapper peas that we sampled had significantly reduced numbers of pods per plant, yield per square metre, and weight of 1000 seeds in the unsprayed plot; this field had the largest population of pea aphids of any field sampled, with aphid numbers peaking at 48.5 ± 9.2 (SE) per plant lip during pod formation and filling. Significant yield losses also occurred in unsprayed plots of a Triumph field, which had a peak aphid population of 4.8 ± 1.6 per plant stem at pod maturation.