Morphological, life history, and distributional data are presented for North American species of the subgenus Stygomomonia (sensu stricto) Szalay, 1943. Adults of the seven previously recognized species are redescribed, and deutonymphs of five of these species are described for the first time. Two species, S. (s.s.) neomexicana Cook and S. (s.s.) occidentalis Cook are substantially revised on the basis of an examination of the types and extensive series of newly collected specimens. Three new species are described, S. (s.s.) californiensis on the basis of deutonymphs and adults, and S. (s.s.) imamurai and S. (s.s.) cooki on the basis of adults. A new diagnosis of the subgenus is proposed and discussed, the relationships of the various species are discussed, and a key to deutonymphs and adults of North American species is presented. New distributional data are presented for all species, and dispersal patterns from Pleistocene refugia are discussed.

The within-cone distribution of Megastigmus spermotrophus Wachtl (Hymenoptera: Torymidae), the Douglas-fir seed chalcid, infesting Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] cones from north-central France was compared with that in samples from California. Results indicate that the mid-region of cones was more intensively utilized by seed chalcids in France than in California, whereas in the northwestern United States the mid-region is characteristically occupied by dipteran and lepidopteran species. This difference in distribution may explain the large discrepancy in infestation rates on the two continents. The potential impact of this finding on pest management strategies is discussed.

Cones were measured and dissected or X-rayed to determine seed chalcid infestation levels. Analysis of covariance performed on data from cones that were collected in 1986 and dissected showed cone diameter at maturity to be a highly significant factor in attack rate, although slopes were different among clones. Between-tree variation was also significant, but clonal source was not. Cone diameter, clonal source, and between-tree variation constituted 87.1% of the variation in rate of attack by the seed chalcid. Although clone was not a significant factor in data from dissected cones, X-rayed cones showed significant differences in attack rates for some clones.

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.

Conspecific host discrimination and larval competition in two aphid parasitoid species were studied in the laboratory using the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), as a host. Aphidius ervi Haliday (Hymenoptera: Aphidiidae) used internal host cues to discriminate between unparasitized and conspecific parasitized hosts. When only parasitized hosts were available, females oviposited into recently parasitized ones where their progeny had a good chance to survive, but rejected those parasitized ≥24 h earlier where their offspring normally died. Competitions occurred only after both eggs had hatched. Larvae eliminated supernumeraries by means of physical combat and physiological suppression. In Aphelinus asychis Walker (Hymenoptera: Aphelinidae), factors, or changes in host internal condition, associated with hatching of the first egg resulted in suppression of conspecific competitors which could be in either larval or egg stage. The older larvae always won competitions through physiological means. A wasp’s oviposition decision is shown to be influenced by the probability of its progeny’s survival. Species that have different reproductive strategies may respond differently to identical host conditions.

Sixteen species of parasitoids were found attacking outbreak and collapsing populations of the jack pine budworm, Choristoneura pinus pinus Free. (Lepidoptera: Tortricidae), in several plots in northeastern and northwestern Ontario. The patterns of parasitism were similar among widely separated plots with only a few species consistently dominating the parasitoid fauna. The greatest difference in the pattern of parasitism was between sustained and collapsing infestations. Collapsing populations of jack pine bud-worm were associated with relatively high levels of parasitism by Meteorus trachynotus Vier. (Hymenoptera: Braconidae) and Lypha setifacies (West.) (Diptera: Tachinidae) which attacked the late larval stages of the budworm. The results are discussed in comparison with other jack pine budworm studies and with spruce budworm population studies.

The effects of root damage by larval cabbage maggots, Delia radicum (L.), on yield of canola, Brassica campestris L., were examined in laboratory experiments. Inoculations of eggs or first-instar larvae resulted in significant root damage. Damage that exceeded 50% of taproot surface area resulted in fewer racemes, fewer productive seed pods on axillary racemes, lower total biomass, and reduced yield of seed. Despite the latter effect, damage that restricts the number of flowering racemes and induces abortion of seed on axillary racemes may increase the efficiency of yield in canola, which flowers indeterminately over a short growing season.

A new species of Proteremaeus, P. nebaikini, is described from Khabarovsk District, Soviet Far East, on the basis of adults. Evidence is presented for considering Sibiremaetts Ryabinin and Krivolutsky. 1975 as a junior synonym of Proteremaeus Piffl, 1965 A key is given to adults of the eight known species of Proteremaeus. Extant members of this genus are known only from the Palaearctic. Thus, a recently discovered fossil specimen of this genus from the late Tertiary, from Ellesmere Island, Canada, has important biogeographic implications which are discussed.

A study was conducted in Butte County of western South Dakota to determine the relationships between habitat characteristics and spatial and temporal changes in community structure of grasshoppers on mixed-grass rangeland. Detrended correspondence analysis (DCA) of 29 undisturbed grasshopper communities and correlation analysis of DCA axis values and habitat variables denned specific spatial gradients underlying the community structure of grasshoppers. Results indicated that grasshopper communities changed along a primary gradient of percentage of coverage of grasses, particularly Buchloe dactyloides (Nutt.) Engelm., and a secondary gradient of percentage composition of clay and sand in the soil.

DCA of 24 grasshopper communities sampled in 1986 and 1987, multiple regression analysis, and factor analysis were used to determine the relationships between specific habitat characteristics and changes in communities of grasshoppers treated with either a nonselective insecticidal spray (malathion) or a selective insecticidal bait (bran bait with carbaryl). Results indicated that between-year change in community composition, or the difference between post-treatment communities in 1986 and 1987, was positively correlated with percentage of coverage of total grasses and forbs. Community malleability, defined as the tendency of a community to return to its predisturbed state, was greater in habitats with high coverages of Agropyron smithii Rydb. and Carex spp., low coverage of Bouteloua gracilis (H.B.K.) Lag. ex Steud., and low species richness of grasses. Our results emphasize the importance of habitat characteristics in structuring undisturbed grasshopper communities and in community change after perturbation with insecticides.

The species of the genus Spilomicrus in America north of Mexico are revised. A generic diagnosis of Spilomicrus, key to genera of Nearctic Spilomicrini, and key to Spilomicrus species in America north of Mexico are given. Four species-groups are defined, viz. distinctus, exul, formosus, and stigmaticalis. Character states, variation, distribution, and relationships of each species are discussed. Twelve of 21 species are recognized as new: S. boweni, S. crassicornis, S. distinctus, S. exul, S. inornatus, S. palustris, S. pumilio, S. robustus, S. sanbornei, S. stepheni, S. superbus, and S. sylvicola. Nine previously known species are redescribed: S. antennatus (Jurine), S. atriclavus Ashmead, S. bifoveatus Kieffer, S. brevicornis (Ashmead), S. flavicornis Ashmead, S. formosus Jansson, S. ruficornis (Provancher), S. stigmaticalis Westwood, and S. virginicus Fouts. The males of S. brevicornis and S. virginicus, as well as the females of S. flavicornis and S. ruficornis, are described for the first time. The following new synonymies are proposed: S. antennatus (= Basalys californica Ashmead), S. atriclavus (= S. foutsi Masner, S. kiefferi Fouts), and S. stigmaticalis (= S. armatus Ashmead).

Two new species of the mite family Erythraeidae (Acari: Prostigmata: Parasitengona) found associated with the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), in Maine are described. Larvae of Leptus treati sp.nov. parasitize spruce budworm adults; L. treati is the first member of the genus to have both larval and postlarval instars described. Adults of Balaustium kendalli sp.nov. prey on spruce budworm eggs; B. kendalli is only the second member of the genus to have both larval and postlarval instars described.

North American species of Agabus Leach of the elongatus-, zetterstedti-, and confinis-groups, as defined by Larson (1989), are revised. Study of character state distribution indicates that the elongatus- and zetterstedti-groups are clades within the confinis-group but the names are retained in this paper to maintain consistency. Twenty species belonging to this complex occur in North America, namely: elongatus-group with A. elongatus Gyllenhal and A. inexspectatus Nilsson; zetterstedti-group with A. zetterstedti Thomson; and the confinis-group with A. thomsoni (J. Sahlberg), A. moestus (Curtis), A. clypealis (Thomson), A. phaeopterus (Kirby), A. immaturus sp.nov. (Great Lakes and Maritime Provinces regions), A. canadensis Fall, A. audeni Wallis, A. mackenziensis sp.nov. (northwestern Canada), A. bicolor (Kirby), A. subfuscatus Sharp, A. discolor (Harris), A. approximate Fall, A. kootenai sp.nov. (southwestern Canada and northwestern United States), A. inscriptus (Crotch), A. smithi Brown, A. sasquatch sp.nov. (alpine areas of California and Nevada), and A. confinis (Gyllenhal). For each species the following information is provided: synonymy; description and illustration of taxonomically useful characters; notes on relationships, variation, distribution, and ecology; and a map of North American collection localities. A key to the North American species of the confinis-group is presented. Lectotypes are designated for A. subfuscatus Sharp, Gaurodytes inscriptus Crotch, G. ovoideus Crotch, and G. longulus LeConte.

The probing behavior of the potato aphid, Macrosiphum euphorbiae (Thomas), is significantly different on potato than on tobacco plants. The higher frequency of short-duration probes, ideal for the transmission of nonpersistent viruses, is the apparent cause for the higher rate of potato virus Y° (PVY°) transmission on tobacco than on potato. However, experimental augmentation of short inoculation probes by M. euphorbiae on potato and tobacco failed to increase PVY° transmission on either. These results demonstrate the absence of a causal relationship between variations in probing behavior of M. euphorbiae and variations in the transmissibility of PVY° by this vector on tobacco and potato.

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.

Adult female Tarsonemus ascitus Delfinado mites are recorded for the first time as phoretic on the grain-inhabiting lathridiid beetles Cartodere constricta (Gyllenhal) and Enicmus fictus Fall, and the rhizophagid beetle Monotoma picipes Herbst. The mites preferred to attach to the lateral and undersides of the prothorax of the beetles. The spatial distribution of T. ascitus on C. constricta in suction traps was determined as a guide to the numbers of beetles that would have to be collected to obtain reliable estimates of numbers of mites found per beetle. The mean numbers of mites per beetle was always smaller than the variance, and the spatial distribution of the mites followed a negative binomial distribution. The numbers of beetles required to be collected to provide a predetermined measure of the precision of the numbers of mites per beetle were calculated.

Temperature-dependent development of the egg, larval, and pupal life-stages of the mountain pine beetle (Dendroctonus ponderosae Hopkins) was described using data from constant-temperature laboratory experiments. A phenology model describing the effect of temperature on the temporal distribution of the life-stages was developed using these data. Phloem temperatures recorded in a beetle-infested lodgepole pine (Pinus contorta Douglas) were used as input to run the model. Results from model simulations suggest that inherent temperature thresholds in each life-stage help to synchronize population dynamics with seasonal climatic changes. This basic phenological information and the developed model will facilitate both research and management endeavors aimed at reducing losses in lodgepole pine stands caused by mountain pine beetle infestations.

Six new species of Mucroseius having adult females phoretic on adult sawyer beetles of the genus Monochamus are described: Mucroseius nipponensis and Mucroseius squamosus from Monochamus alternatus Hope in Japan, Mucroseius algonquian from three species of Monochamus in eastern Canada and eastern United States, Mucroseius disparisetus from Monochamus titillator (Fabricius) in southeastern United States, Mucroseius Californicus from Monochamus clamator (LeConte) in California, and Mucroseius mexicanus from Monochamus rubigineus (Bates) in Mexico. Mucroseius aciculatus (Ishikawa, 1968), new combination, from Mecynippus pubicornis Bates in Japan, and the type-species, Mucroseius monochami Lindquist, 1962, from several species of Monochamus widely distributed in North America, are redescribed. Misidentifications of these species in the Japanese and North American literature are noted, and a key is given for these eight species. One adult female of an undescribed species found on a sawyer, Monochamus sutor Linnaeus, from Europe, is noted as possibly belonging to Mucroseius.

The taxon Mucroseius is redescribed, and its problematic status as a genus is reviewed. The phylogenetic position of Mucroseius, which appears to be derived within the genus Proctolaelaps, is discussed. Previous observations on biological and ecological aspects of Mucroseius mites, including those published in Japanese, are critically reviewed, with new data added for host ranges and specificities, distribution, phoretic behavior, occurrence in sawyer gallery systems, mode of reproduction, and their association with the pine wood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle. Cheliceral structure and speculations on the feeding habits of these mites are discussed; however, feeding preferences have not been clarified.

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.

The effects of Bacillus thuringiensis var. israelensis de Barjac (B.t.i.) on the feeding habits of two black fly predators, Nigronia serricornis (Say) and Acroneuria lycorias (Newman), and a detritivore, Prostoia completa (Walker), were examined. We assessed whether B.t.i.-killed and hot water-killed black fly larvae were less or more desirable to these consumers than live larvae. Nigronia larvae showed no significant differences in predation on larvae within the three categories. Acroneuria nymphs consumed more live than dead prey. Experiments with the detritivore, Prostoia, showed that they preferred dead black fly larvae to live ones. Bacillus thuringiensis var. israelensis treatment may have little direct effect on nontarget organisms, but these studies indicate that there still may be consequences for predators and detritivores when a viable population of larval black flies is transformed into dead organic matter.

Mistblower applications of permethrin at 70 g AI per hectare to individual white spruce trees near the onset of the hatching period reduced spruce budmoth, Zeiraphera canadensis Mut. and Free., larval populations by 90% and damage to leaders to a very acceptable index of 0.49. A dosage of 35 g AI per hectare was less effective but did provide acceptable leader protection (damage index: 0.93). Further mistblower trials, designed to determine the optimum time to spray with permethrin, demonstrated that at 70 g AI per hectare, effective control (87–94%) and acceptable protection (damage indices: 0.87–1.13) were obtained during a 9-day period before the onset of hatch. An earlier treatment. 11 days before hatch, did not provide as effective control (58%) or acceptable protection (damage index: 1.60). Two later treatments, 3 and 4 days after the onset of hatch, gave less effective control (75–79%) but did provide acceptable leader protection (indices: 0.83–1.17).

Siculaphis vittoriensis gen.nov., sp.nov., Myzocallis (Hoplocallis) microsiphon sp.nov., and M. (Agrioaphis) cocciferina sp.nov. are described. The new taxa have a Mediterranean distribution, and Quercus calliprinos Webb is their main host. Accounts are given of their morphology, taxonomic position, and ecology. A key is presented for the four species in the subgenus Hoplocallis.