Chironomus riparius was used to determine whether an increased frequency of chromosome aberrations could be detected in the progeny of an aquatic organism reared in tritiated water (HTO). An increased frequency was detected in larvae whose progenitors had developed either in 250 or 500 μCi/ml of HTO (2500 to 5000 times MPC for occupational exposure). The radiosensitivity of C. riparius to acute gamma radiation was determined and compared with the results obtained with tritiated water. The frequency of aberrations produced by incorporated tritium was approximately the same as the frequency produced by an equivalent dose of chronic gamma irradiation.

The potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), is a host-alternating species and an important pest of Canadian flax. Populations of this aphid are highest in flax when the weather is warm and dry in July. Field-plot studies show that populations of the potato aphid increase rapidly in late July and early August and decline rapidly in mid-August. In some years potato aphids die because of a fungal epizootic or drought-induced senescence of the crop, but usually these factors do not account for the population decline. Field cage studies show that the potato aphid emigrates from the crop in mid-August. The photoperiodic response of the potato aphid and resulting emigration explain the population decline in flax, which occurs in mid-August each year regardless of the growth stage of the crop, population density, or average temperature at the time of the photoperiodic cue. Male and mating female potato aphids, born at the end of August, have time to develop, mate, and lay eggs before temperatures drop below the developmental threshold. The population decline assures that farmers need not sample or control the potato aphid in flax after mid-August.

Below-ground herbivores have been poorly studied regardless of their importance for the establishment and composition of plant communities. In a subalpine grassland associated with a 3200-m-elevation pine forest in central Mexico, the composition and vertical and horizontal distribution of the macroarthropod root-feeding community was studied for 14 months. The root-feeding community included six species of Coleoptera and one species of Diptera. The dominant species were Phyllophaga spp. (subgenus Phytallus, "macrophylla" group) and Trachyploeomimus aff. spurcus Champion. Mean density and biomass of this community were 101 individuals and 3 g per square metre, respectively. These values were low when compared with those reported for other communities. Species were most abundant in the first 10 cm of the soil all year around. Dominant species showed a clumped horizontal distribution most of the year.

The taxonomy, distribution, and ecology of the Holarctic species of Agabus (Coleoptera: Dytiscidae) are reviewed. Seventeen species occur in both the Nearctic and Palaearctic regions. The following new synonymy is proposed (valid name given last): A. solus Leech = A. adpressus Aubé; A. sharpi Jacobson and A. pseudoconfertus Wallis = A. opacus Aubé; A. kenaiensis Fall = A. wasastjernae (Sahlberg) and A. hudsonicus Leech = A. zaitzewi Poppius, thus each of these species is recognized for the first time as being Holarctic. The Nearctic species A. ontarionis Fall is reduced in status to a subspecies of A. fuscipennis (Payk.). Agabus congener (Thunb.) is redefined and Nearctic specimens formerly placed in the species are assigned to A. thomsoni (J. Sahlberg). The reports of Palaearctic occurrence of A. approximates Fall and A. discolor (Harris) are considered to be in error, the records referring to A. levanderi Hellén.

Females of Eupteromalus dubius (Ashm.) oviposit on pupae of cyclorrhaphous Diptera and the larvae develop gregariously as ectoparasites. Details of the life history of E. dubius are described. A progressively lower percentage of female progeny of E. dubius matures as the parasite:host ratio increases. Three mechanisms that may cause this sex ratio change are examined and discussed.

A larval population of spruce budworm, Choristoneura fumiferana (Clemens), was monitored for 5 d following aerial application of a commercial formulation of Bacillus thuringiensis Berliner subsp. kurstaki to investigate dose acquisition and expression (larval mortality, recovery, feeding, and growth) in relation to spray deposition and persistence of spray deposits. The main objective was to test if previous laboratory observations on how B. thuringiensis affects feeding and dose ingestion by spruce budworm larvae hold true under field conditions. About 40% of the treated population ingested a lethal dose within 1 d after spray application. Lethally dosed larvae died without further feeding upon transfer from treated foliage to (untreated) artificial diet. Resumption of feeding by larvae that survived the treatment was delayed relative to larvae from the control population during 3 d following spray application; during that time, normal feeding activity and larval weight gain were suppressed. Inhibited feeding by survivors appeared to prevent further dose uptake because the proportion of lethally dosed larvae in daily collections did not increase despite significant residual spray deposits in budworm feeding sites. Restoration of "normal" recovery times by the fourth day coincided with a 65–85% reduction in persistence of the pathogen on the foliage and did not result in further lethal dose acquisition, as treatment-induced mortality dropped to about 20% on the 4th and 5th days. The observations are consistent with previous laboratory observations of how B. thuringiensis affects larval feeding and with the hypothesis that feeding inhibition may be a limiting factor in the acquisition of a lethal dose.

A cattle-baited (C-B) trap and a Trueman–McIver (T-M) segregating CO2 trap provided information on seasonal abundance, host-seeking activity, and blood-feeding of biting-flies near St. John's, Newfoundland. A total of 19 682 biting-flies (26 species) were collected (C-B trap = 11 407; T-M trap = 8275) from 26 May to 16 September 1982. Black-flies (Simuliidae) comprised 94.1% of the total sample (C-B trap = 10 747; T-M trap = 7773). Mosquitoes (Culicidae), biting midges (Ceratopogonidae), and tabanids (Tabanidae) comprised the remainder. Blood-fed flies represented 54.7% of the total catch in the C-B trap, but the proportion varied considerably among species. Black-fly activity was concentrated in June and July, though flies were also collected in May, August, and September. Prosimulium mixtum was the predominant species in June and Simulium venustum/verecundum complex was the major pest in July. Prosimulium mixtum was most active from mid-morning to late-afternoon, with little evening activity. Simulium venustum/verecundum complex showed 2 peaks of activity, one in the morning and another in the early evening. A few P. mixtum and S. venustum/verecundum complex were active after dark. Captures from the T-M and C-B traps were compared to test the reliability of the T-M trap as an indicator of activity of biting-flies attracted to cattle. Significant correlations (P < 0.001) between the number of flies collected in the 2 traps were found for P. mixtum and S. venustum/verecundum complex. Remaining species were taken in numbers too low for analysis.

All Cardiophorus species found in Canada and the United States of America east of the Rocky Mountains are keyed and all but those with the majority of their ranges west of the Rocky Mountains are revised. Eleven species are recognized, three of which are new to science (C. catskillensissp. nov., C. destinensissp. nov., and C. panamapolissp. nov.). Cardiophorus floridae Candèze and C. angustatus Blanchard are synonymized under C. convexus (Say). All 11 are described and taxonomically important characters are presented. Distribution maps are presented for each species. The following lectotypes are designated for species that were described from more than one specimen without former holotype designation: C. angustatus, C. floridae, C. erythropus Erichson, C. gagates Erichson, C. togatus Horn, C. robustus LeConte, C. convexulus LeConte, and C. amictus Melsheimer. The following neotypes were designated to replace destroyed type specimens: C. cardisce (Say) and C. convexus.

Ontogeny, interspecific homogeneity, and intraspecific variability of female genitalic and other characters of North American Cybaeus L. Koch spiders are described and used to resolve taxonomic problems in the genus. Ontogenetic changes in spermathecal duct morphology occur as females mature and age. Three distinct ontogenetic stages are described: pre-epigynum/pre-vulva, subadult / teneral adult, and mature adult. Concordant with aspects of sexual selection theory, closely related females may be morphologically indistinguishable. Many Cybaeus species exhibit a wide range of body size. Within single species, ontogenetic stages and outlier size classes have been described as separate species. Species with similar females have been lumped under one name. Based on this, 10 new synonyms are proposed for North American Cybaeus: C. adenoides Schenkel = C. grizzlyi Schenkel; C. chaudius Exline and C. hatchi Exline = C. shoshoneus Chamberlin and Ivie; C. exlineae Chamberlin and Ivie = C. bulbosus Exline; C. hystrix Chamberlin and Ivie = C. cribelloides Chamberlin and Ivie; C. janus Chamberlin and Ivie = C. eutypus Chamberlin and Ivie; C. marinensis Chamberlin and Ivie and C. angelus Chamberlin and Ivie = C. consocius Chamberlin and Ivie; and C. olympiae Exline and C. tius Chamberlin and Ivie = C. reticulatus Simon. In addition, four old synonyms are rejected: C. grizzlyi Schenkel and C. adenoides Schenkel ≠ C. adenes Chamberlin and Ivie; C. patritus Bishop and Crosby and C. silicis Barrows ≠ C. giganteus Banks.

Several resistant lines of wheat, Triticum aestivum (L.) (Poaceae), have been developed to control populations of the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae). We examined the potential effects of D. noxia resistant lines on another aphid, the bird cherry-oat aphid (Rhopalosiphum padi (L.) (Hemiptera: Aphididae)), which commonly co-occurs with D. noxia. Because one type of resistance (mediated by the Dn1 gene) is purported to be induced rather than constitutive, we also determined the degree to which the suitability of resistant and susceptible plants is modified by previous infestation. Although resistant lines were derived from five different sources, we did not detect any differences in the population growth of R. padi on resistant and near-isogenic susceptible plants. The performance of D. noxia was reduced as expected on resistant plants but was unaffected by whether or not plants had been previously infested. In contrast, the performance of R. padi was reduced on plants that had been previously infested but was unaffected by whether plants were resistant or susceptible to D. noxia. Because neither species' performance was especially low on previously infested, resistant plants, there was no evidence that prior aphid feeding induces a higher level of resistance.

Neem seed extract (20, 60, and 180 ppm azadirachtin) applied to the crowns of black spruce trees immediately prior to female reproductive bud flush, resulted in high mortality of early instar spruce budworm larvae. Dose-dependent reductions of 40–93%, as compared with check trees, were observed 2 and 4.5 weeks after treatment. Seed cone protection from grazing damage, however, was moderate; at 60 ppm azadirachtin, the incidence of cone grazing was reduced 29%, and the proportion of severely grazed cones reduced 39%, as compared with check trees. Larval mortality and bud damage observed in the laboratory corroborated field results. High toxicity to second-instar larvae, and performance during adverse weather conditions, supports the potential of neem seed extract for control of spruce budworm defoliation. However, both laboratory and field results indicate that feeding occurs before the effects of neem seed extract manifest, resulting in moderate protection of cones. Whereas foliage can tolerate low levels of feeding, female strobili are damaged significantly. Excellent protection of foliage was achieved from systemic injections of neem seed extract to white and black spruce trees (1.5 g azadirachtin/tree). Neem seed extract, formulated for systemic application, could provide a botanical alternative for control of forest pests in urban environments.

The mating behavior of spruce budworm [Choristoneura fumiferana (Clem.)] moths was studied in a wind tunnel. Of 88 contacts between male and female moths, 64 (73%) resulted in successful copulation. Failures were a result of males losing contact during courtship (11%), and females walking or flying, either when first contacted (7%) or when males attempted copulation (9%). Females showed no overt behavior other than moving away. Removal of the male labial palps had no effect on responses, which indicates that these structures have no role in courtship. Males with antennae completely removed did not respond to airborne pheromone and, therefore, none copulated. Removal of one antenna or half of both antennae of the males did not reduce the numbers of males that located females, but did result in slower responses and fewer matings. It also resulted in changes in male courtship behavior, which suggest that males depend upon their antennae to position themselves appropriately alongside the female when attempting to copulate. Analyses of male response to models of female moths constructed from glass rods with wings of male spruce budworm or male white-marked tussock moth [Orgyia leucostigma (J.E. Smith)] attached showed that males position themselves approximately halfway along me wing length of the model, with no dependance on its wing size or the length of the male’s antennae. Responses were equally high to both spruce budworm and to tussock moth wings, but no males responded to glass rods in the absence of wings.

Dendroctonus rhizophagus sp. n. collected from small pine trees in Mexico is described. Notes on seasonal development and habits are given.

Observations on Malus domestica (Borkh) in central Ontario between 1981 and 1984 revealed that dogwood borer (Synanthedon scitula Harris) larval feeding was primarily associated with burr knots on the above-ground portion of apple rootstocks. Trunk injuries also served as sites of entry. Monitoring with pheromones indicated moth emergence occurred from late June until early August with peak activity occurring near the middle of July. Control of the dogwood borer on apple was obtained with 2 trunk drench sprays of dimethoate, fenvalerate, permethrin plus oil, endosulfan, parathion, chlorpyrifos, or lindane when applied during the period of adult flight activity.

A mathematical model relating mosquito densities and meteorological variables is given. The model is developed from observations on a real mosquito population and forecasts future mosquito densities from information about mosquito densities, amount of rainfall, and temperature at past points in time.

Pieris occidentalis nelsoni W. H. Edwards from Fairbanks, Alaska, was reared under a variety of photoperiod–temperature regimes. The source population is presumably univoltine and monophenic, with a phenotype resembling the vernal one produced by multivoltine, diphenic P. o. occidentalis Reakirt in Colorado and California. Photoperiods of 10 or 15 h produced 100% diapause pupae at 15 °C and circa 65% at 25 °C. Under continuous light 22% diapaused at 15 °C and < 1% at 25 °C. About 20% of non-diapause pupae produced adults resembling the estival phenotype of P. o. occidentalis, which is unknown in wild P. o. nelsoni. Although nelsoni is more likely to diapause than the nominate subspecies from the Sierra Nevada, its potential for direct development and polyphenism is interpreted as evidence that it is derived from a multivoltine ancestor.

Male. Head and thorax shiny black wiith slight brown shading on the pleural sutures. Abdomen dorsally deep black-brown with the anterior portion of segments 4-7 faintly pale, hyaline, and with traces of a broken dark supraspiracular band; ventrally scarcely paler with similar hyaline areas and traces of small black spots in the postero-lateral corners of the middle segments. Legs deep brown Setae dirty white ringed with dark brown. Wings hyaline with pale brown longitudinal veins; the crossveins pale, except in the costo-apical region. Length of body 7 mm.; of wings 7 mm.

The last-instar larvae of 13 species of Loxostege Hbn. are described and a key included to separate them to species. Notes on the life histories and habits have been added where these are available. One, L. sticticalis (L.), the beet webworm, often causes damage in commercial beet fields. The other species involved in this present work are: L. coloradensis (G. & R.), L. chortalis (Grt.), L. pseudobliteralis Capps, L. marculenta (G. &. R.), L. mancalis (Led.), L. helvialis (Wlk.), L. bifidalis (Fabr.), L. rantalis (Gn.), L. allectalis (Grt.), L. cereralis Zell., L. albiceralis (Grt.), and L. floridalis B. & McD.

A growing body of evidence suggests trophic generalism (feeding on resources from more than one trophic level and/or on different resources of the same trophic level) is a widespread feature among ground beetles (Coleoptera: Carabidae). However, it remains unclear whether trophic generalism applies to single individuals, at the intrapopulation or interpopulation level. Here we present stable isotope data (δ15N, δ13C) of seven common European carabid species on an archipelago of 18 lake islands in northeastern Poland. We found strong differences in isotopic ratios between individuals of the same population as well as between different populations, indicating that carabids are opportunistic feeders and that the degree of opportunism differs between habitats and between islands. Trophic niche breadth as assessed by isotopic ratios was influenced by local habitat diversity. We suggest that opportunistic usage of different local resources results in striking differences between local populations and a very broad trophic niche observed at regional level.

Laboratory bioassays were carried out on two species of phytoseiid mites to investigate their resistance to the fungicide mancozeb. Susceptible and suspected resistant strains of Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten were tested. Mancozeb resistance factors were low to moderate: they reached 6.3 and 11.7 for K. aberrans and T. pyri, respectively. Intrinsic toxicity of mancozeb was approximately 5–10-fold more pronounced in females of K. aberrans than in females of T. pyri. The female susceptibility pattern of the most resistant strain of K. aberrans was quite close to that of the most susceptible strain of T. pyri. The LC50 values for the most resistant strains of K. aberrans and T. pyri were 4.6 and 43 times higher, respectively, than the maximum field application rate of mancozeb recommended for control of downy mildew in vineyards. Using a diagnostic concentration, a limited survey in vine plots indicated that most of the K. aberrans strains we tested were susceptible to mancozeb, but a few consisted of both resistant and susceptible individuals. All strains of T. pyri collected in Burgundy were susceptible. Half of the T. pyri strains from Bordeaux were susceptible and the other half were mixed populations of resistant and susceptible individuals.