The foraging behaviour of honey bees (Apis mellifera L.) on inflorescences of staghorn sumac [Rhus hirta Sudworth (ex-typhina L.)] was studied using a “choice table” placed in natural stands of this plant. The choice table consisted of a wooden grid with alternated male and female inflorescences of sumac. Honey bee activity was recorded also on inflorescences of naturally growing plants in which the secretion of nectar was measured and the anther dehiscence recorded. Honey bees were the only common pollinators observed on sumac in the study area. During the morning, both plant sexes secreted little nectar, and pollen was available after the dehiscence of the anthers which took place between 1000 and 1100 hours. Female inflorescences secreted great amounts of nectar during the afternoon, but in male inflorescences there was little secretion. Honey bees seemed to forage according to the circadian availability of resources. Most of their activity concentrated on male inflorescences in the morning and on female ones during the afternoon. Both the occurrence of bees with pollen loads in their corbiculae and the length of the visits to each sex also seemed to be in accordance to the kind of resource exploited at particular times of the day. Most of the bees with pollen loads were observed during the morning and the longest visits to any inflorescences were registered on female ones during the afternoon (by bees foraging for nectar). Despite our results suggesting that the pollination success of staghorn sumac would be impaired by the foraging pattern of honey bees, an explanation is proposed for its reproductive success.

Species in the family Aphidiidae (Hymenoptera) parasitize exclusively ovoviviparous aphids. Females use a variety of information to detect and evaluate suitable hosts. Olfactory cues associated with aphids, or the aphids’ host plant, are important for host location. Visual cues including aphid colour, shape, and movement can be evaluated from a distance without physical contact; aphid movement may act as a releasing stimulus for attack. Contact chemosensory cues (gustatory cues) are evaluated by antennation of the host cuticle and during ovipositor probing. A potential host must conform to the wasp’s response profile and satisfy minimum physiological and dietary requirements for immature development and growth. Host quality is determined in part by attributes specific to each aphid species and in part by each aphid’s individual-specific growth potential. Host quality for male and female progeny may vary as a result of different patterns of resource allocation and sexual size dimorphism. For an encountered aphid to be accepted as a host, its perceived value must exceed the wasp’s response threshold for oviposition. Host value, as opposed to host quality, varies dynamically with parasitoid state variables such as age, egg load, and prior experience. A conceptual model of host choice by aphidiid wasps is presented.

Feeding preferences of the white pine weevil, Pissodes strobi (Peck), for resistant or susceptible Sitka spruce, Picea sitchensis (Bong) Carr., were investigated using three types of laboratory bioassay. In paired-twig bioassays, fall weevils were significantly deterred from feeding up to 80% by resistant clones from four British Columbia provenances: Green Timbers, Cedarvale, Haney, and Big Qualicum. Females showed greater discrimination than males. Spring weevils were deterred from feeding by clones from the Green Timbers and Big Qualicum provenances by up to 60%. Fall males were more consistently deterred than spring males, suggesting that some host selection occurs in the fall. Females were significantly deterred from ovipositing on twigs from one clone from Big Qualicum, and stimulated by clones from Cedarvale when given a choice. Given no choice, however, they were significantly deterred from ovipositing, but not feeding by several resistant clones. In agar-disc bioassays, spring weevils were significantly deterred from feeding by bark from the provenances of Cedarvale and Big Qualicum by up to 86%. Trees from the provenances of Big Qualicum and Green Timbers caused the most consistent feeding or oviposition deterrency and may rely on this in part as a resistance mechanism. Because not all resistant clones and provenances were deterrent, we hypothesize that these trees may employ other resistance mechanisms which could be incorporated along with feeding and oviposition deterrency into breeding for resistance.

Insects are selected for slow development (but relatively fast growth) in spring, but for fast development in summer. These contrasting selection pressures explain five puzzling effects of temperature on insects: growth and development rates increase almost linearly with temperature; genetic variability in development rate is reduced at high (27°C) temperatures; genetic variability in growth rate is reduced at low (15°C) temperatures; development is very slow at the time of emergence after diapause, regardless of the temperature threshold for emergence; and growth is slow at low temperatures, but development is even slower.

Insects use temperature to indicate time-of-season. Different species are geared differently to rising temperatures. Insect predators and parasitoids become more effective at high temperatures; and insect population dynamics are not stable in the conventional sense.

Diets combining the eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) with corn pollen, green snap bean pods, and adult western flower thrips [Frankliniella occidentalis Pergrande (Thysanoptera: Thripidae)] were evaluated for their effects on the predatory anthocorid bug Orius insidiosus (Say). Nymphs fed only corn pollen did not complete development. Fourteen percent of the nymphs fed only green bean pod sections reached the adult stage. Females reared on a diet of bean pod sections did not oviposit. Nymphal survival, adult longevity, and fecundity were greatest for diets containing both E. kuehniella and green bean pods. When diets of bean pod sections and eggs of E. kuehniella were supplemented with pollen, egg production was slightly increased. Adult females provided with thrips were not more fecund than females maintained on a diet of eggs of E. kuehniella. Egg production increased significantly with the number of thrips consumed, demonstrating the importance of adult nutrition.

Oviposition and fecundity of the pine false webworm, Acantholyda erythrocephala (L.), were investigated in the field and in controlled environments in the laboratory. Females mated and began ovipositing soon after emergence from the soil. Most eggs were mature and ready for deposition at female emergence. Potential fecundity of females at emergence from the ground was a linear function of adult wet or dry weight. However, a few eggs matured following emergence of the females from the soil. The amount of defoliation of the host plant caused by the sawfly in the previous year was inversely related to size and potential fecundity of emerging adults.

Realized fecundity was independent of temperature over the range of rearing temperatures examined. Mean realized fecundity at constant temperatures ranged from 32.9 eggs per female at 14.9°C to 42.0 eggs per female at 26.6°C. These differences were not statistically significant. Oviposition and ageing rates were temperature dependent. Average female longevity ranged from 27 days at 14.9°C to 6.6 days at 26.6°C. Females were diurnal and oviposition occurred during daylight hours. Oviposition pattern of the sawfly was described by a model based on temperature-dependent oviposition and ageing-rate functions. The model accurately predicted female survival and egg deposition in an outdoor insectory. However, predicted oviposition pattern of natural populations was delayed when compared with the observed pattern and may have resulted from microclimatic effects or inaccuracy of the model at low temperatures.

Triarthria Stephens is known from two species in the New World. One is T. setipennis (Fallen), introduced into North America from Europe early this century as a biological control agent against its host, the European earwig (Forficula auricularia L.) (Dermaptera: Forficulidae). The second species is T. parva (Townsend), a widely distributed earwig (Doru spp.) parasitoid in the Neotropical region. Triarthria parva was originally described in the monotypic genus Parkerella Townsend; Parkerella is newly synonymized with Triarthria (syn.nov.), and T. parva is a new combination (comb.nov.). The genus Triarthria is diagnosed and the four included species are keyed: T. legeri (Villeneuve) (western Palearctic region), T. tienshanensis Ziegler (Uzbekistan), T. setipennis, and T. parva. The two species in the New World are diagnosed, illustrated, and their known distributions mapped.

In the genus Ephoron of Japan three species are recognized: E. shigae (Takahashi), E. limnobium sp.nov., and E. eophilum sp.nov. This study includes a key to the species, a description of each species, and maps of species distributions.

In a 3-year field study, potted plants of ‘Katepwa’ wheat, Triticum aestivum L., were exposed to ovipositing wheat midge. Sitodiplosis mosellana (Géhin), to determine when spikes are most susceptible to damage. After exposure, plants were maintained under controlled conditions for 4 weeks and examined for wheal midge larvae and damaged kernels, ‘Katepwa’ wheat became susceptible to wheat midge damage shortly after spikes emerged from the boot leaf. Location of larvae and damaged kernels within spikes was influenced by the duration spikelets were exposed to oviposition and pattern of anthesis within spikes. In 1992, frequencies of larvae and damaged kernels were 60–90 times higher in spikes exposed to oviposition during advanced heading (stages 57–59, Zadoks’ code) than in those exposed during flowering (stages 61–69). Kernel damage in spikes exposed to oviposition during stages 57–59, 61–65, and 65–70 was 48.5, 3.2, and 0.2%, respectively, in 1993 and 21.2, 1.0, and 0.6%, respectively, in 1994. Data indicated that susceptibility to midge damage declined 15- to 25-fold between heading and early anthesis and 35- to 240-fold between heading and advanced anthesis. Potential factors contributing to these declines and concomitant reductions in larval frequencies are discussed.

Commercial fields of ‘Katepwa’ wheat should be monitored for ovipositing wheat midge throughout heading (stages 51–59) when spikes are most vulnerable to damage. Larval survival and kernel damage were so low after stage 61 that monitoring during anthesis should be unnecessary. Intensive inspection of fields throughout heading would ensure that chemical treatments are applied when they are necessary and most effective.

Conophthorus radiatae Hopkins, Ernobius punctulatus Fall, and Pityophthorus spp. infest cones and twigs of Monterey pines (Pinus radiata D. Don) and thus may be important vectors of the pitch canker fungus Fusarium subglutinans f. sp. pini in the central coast of California. Fifteen percent of 1st-year Monterey pine conelets infested with C. radiatae prior to August 1990 developed pitch canker by May 1991. Conophthorus radiatae, E. punctulatus, and Pityophthorus spp. were dissected from some of these conelets and found carrying F. s. pini. Between June 1990 and May 1991, 16% of 695 randomly selected uninfested 1st-year conelets from a total of 329 separate cone whorls were infested by at least one of the above beetle species, and F. s. pini was isolated from 42% of the attacked conelets. Average percentage contamination of beetles per conelet was highest for adults of Pityophthorus spp. (38%), followed by adults of C. radiatae (33%), larvae of E. punctulatus (24%), and larvae of Pityophthorus spp. (5%). There were significant associations between conelets that contained contaminated C. radiatae, Pityophthorus spp., and/or E. punctulatus and conelets with F. s. pini.

Under experimental conditions, C. radiatae and E. punctulatus transmitted the fungus to healthy cones. Ernobius punctulatus required an entrance tunnel by C. radiatae to enter and infect the cone. Artificially wounded cones did not develop pitch canker. Intra- and interspecific transmission of F. s. pini was demonstrated among these beetle species. In infested branch tips without cones, interspecific transmission of F. s. pini between E. punctulatus and Pityophthorus spp. was also demonstrated.

The roles of C. radiatae and E. punctulatus as vectors of F. s. pini and of Pityophthorus spp. as potential vectors are discussed in relation to the epidemiology of pitch canker disease. The spread of pitch canker to California’s native pines as well as other conifers may be enhanced by interspecific transmission of F. s. pini between E. punctulatus and C. radiatae in cones and between E. punctulatus and Pityophthorus spp. in branch tips. Ernobius punctulatus provides a pathway for the fungus to potential insect vectors that attack several hosts and a variety of plant parts.

The amount and distribution of foliar feeding injury by adult potato flea beetles, Epitrix cucumeris (Harris), were examined on individually caged potato plants grown in field plots in Manitoba. Plants were either maintained as uninfested controls, or were exposed throughout the growing season to different insect densities that mimicked the natural seasonal pattern of infestation. In 1984, a trial was conducted using cv. ‘Norland’ exposed to four different densities of potato flea beetles. In 1989 and 1990, cv. ‘Russet Burbank’ was exposed to potato flea beetles, and in some treatments, plants were exposed to early summer infestations of Colorado potato beetles, Leptinotarsa decemlineata (Say). In each trial, during the late summer period of high potato flea beetle density, the amount and distribution of flea beetle feeding injury were assessed at weekly intervals. Counts of feeding punctures in single leaflets were made from leaves in the upper, middle, and lower third of each caged plant, and these data were subjected to repeated measures analysis of variance. In each of the 3 years, increasing the number of flea beetles increased the mean number of feeding punctures per leaflet in an approximately linear fashion; however, the number of punctures per beetle varied between cultivars and years. In 1984 and 1990, the number of feeding punctures per leaflet was least in the upper third of the plants, and greater in the lower, or middle and lower, third of plants. However, in 1989, the vertical distribution of feeding punctures was relatively even. Previous feeding by Colorado potato beetles increased the mean number of flea beetle feeding punctures per leaflet and changed the vertical distribution of feeding punctures. Rainfall and temperature were correlated with patterns of flea beetle injury; injury was concentrated on lower leaflets during weeks of greater rainfall, and upper leaflets were injured most during weeks with higher average temperatures. It is concluded that flea beetles exhibit preferences for feeding in specific portions of potato plants, and that these preferences change in response to previous defoliation and are influenced by meteorological conditions. Consequently, counting feeding punctures would not be a reliable method of assessing whether control measures for potato flea beetles are justified.

The life cycle, phenology, and abundance of Epuraea obliquus Hatch was studied near Hinton, Alberta. Most of the life cycle occurs on galls of Endocronartium harknessii (J.P. Moore) Y. Hiratsuka (western gall rust) infecting lodgepole pine (Pinus contorta Dougl. var latifolia Engelm.). Both adults and larvae feed on the spores of the fungus. Individuals of this beetle were found on most galls sampled. Adults overwinter in the soil. They emerge in the spring to seek out and colonize galls. Eggs are laid on the surface of galls, mainly under the periderm, and larvae feed on the fungus, developing through three larval instars. Larvae in the last instar drop from galls to pupate in the soil. Adults leave the soil in late summer and return to feed on inactive galls before overwintering in the soil. The phenology of E. obliquus is closely synchronized with the timing of rust sporulation and the impact of beetle feeding may be an important natural control of western gall rust.

Eggs of blueberry leaftier, Croesia curvalana (Kearfott), were transferred from outdoors at 15-day intervals from 15 November to 1 March and held in the laboratory at 20°C, 16L:8D. Mean hatching time continually decreased with each successive transfer date and was significantly shorter for eggs transferred on 1 March compared with any previous transfer date. Transfer date also had a significant effect on percentage hatch, which generally increased with longer exposure of eggs to outdoor conditions. Mean hatching time was longer under 10L:14D photoperiod than at 13L:11D or 16L:8D conditions at all three temperatures studied. Rate of postdiapause development was linearly related to constant temperatures in the range from 6 to 25°C, but appeared to have deviated from linearity at 30°C. The lower threshold temperature for postdiapause development of eggs was estimated to be 3.4°C. Means of 60, 77, and 97 degree-days above a lower threshold of 3.5°C were required for hatching of the 10th, median, and 90th percentile of eggs under laboratory conditions, respectively. In each of 3 years, eclosion of first-instar larvae occurred over a 10- to 17-day period in late April to mid-May. Degree-day accumulations based on litter temperatures in the field predicted the dates of 10th, 50th and 90th percentile eclosion of first-instar larvae within ±2 days of the observed dates.

We determined variations in selected life-history parameters in a tritrophic system that consisted of a plant (broad bean, Vicia faba L.), an aphid (pea aphid, Acyrthosiphon pisum), and an aphid parasitoid (Ephedras californicus). We manipulated plant and aphid quality by growing bean plants in a high- and a low-quality nutrient solution for three generations. Pea aphids adapted to reduced nutrient availability by differentially allocating resources to somatic and gonadal growth across generations. On low-quality plants, time from birth to adult increased and dry mass decreased. The number of sclerotized embryos was correlated with adult dry mass. By contrast, in E. californicus, variations in dry mass, rate of development, and number of ovarial eggs did not suggest transgenerational adaptations to resource quality as measured by aphid size. The number of mature eggs was dependent on female age. Development time varied with parasitoid sex and was independent of aphid stage at the time of death. In the low-quality treatment, males survived on average longer than females eclosing from the same kinds of hosts.

Aphids and their parasitoids have evolved flexible life-history strategies in response to variations in plant quality. Pea aphids adapted to qualitatively variable resources by optimizing the balance between somatic and gonadal investment across successive generations. But E. californicus responded to low host quality at the level of the individual, rather than across generations; the trade-off pattern was influenced by the host’s growth potential after parasitization.

Nine new species and one subspecies of Palmanura from Mexico and Guatemala are described and illustrated: P. matildae, P. lindquisti, P. schusteri, P. lacandonicus, P. curta, P. pascuali, P. wilsoni, P. normae, P. colotlipa, and P. mirabilis longa. Besides the new taxa, new records and a key for the 12 known species of the genus are given. A brief discussion on the distribution and evolution of this and related genera is included.

The seasonal phenology of the walnut husk fly (WHF), Rhagoletis completa Cresson, was studied in the Willamette Valley of Oregon during a 4-year period (1990–1993). Adult emergence observed in ground emergence cages varied greatly among years. Initial emergence ranged from 29 June to 17 July, and last emergence occurred as early as 17 August or as late as 11 September. The period of adult emergence was constant from year to year (mean 55, range 50–60 days) with the peak between the 3rd week of July and the 1st week of August. The period between first observed appearance of females in ground-level emergence cages and the first oviposition was consistent among the study years, ranging from 20 to 23 days. Peak oviposition occurred in the 2nd and 3rd weeks of August. Mean egg hatch and larval survival were 98 and 80%, respectively. Infestations reached over 95% in unsprayed trees by early to mid September. Mature larvae first exited from husks beginning the 4th week of August and continued through mid October. Larvae penetrated the soil and pupated at a depth of 2.5–7.6 cm with most within the top 2.5 cm of soil.

Impacts of Bacillus thuringiensis var. kurstaki (Btk) and defoliation by gypsy moth [Lymantria dispar (L.)] on native, non-target arthropods were evaluated in eastern West Virginia from 1990 to 1992. Adult and larval arthropods were collected by foliage sampling and light-trapping at 24 20-ha (50-acre) plots, representing six replicates of four treatments: unsprayed, gypsy moth absent (control); unsprayed, gypsy moth present (defoliation); sprayed, gypsy moth absent; and sprayed, gypsy moth present. Pre-treatment data were collected in 1990. In May 1991, one application of Btk was made to 12 plots at a dosage of 14.4 BIU/ha (36 BIU/acre). Post-treatment data were collected in 1991 and 1992. With few exceptions, detectable effects from Btk application were restricted to Lepidoptera. Although abundance and species richness of larval and adult non-target Lepidoptera decreased at all plots between 1990 and 1992, abundance and species richness were reduced at Btk-treated plots relative to untreated plots. Richness and abundance of some larval and adult Lepidoptera declined at defoliation plots. Although the short-term (< 1 year) impacts of Btk application on non-target Lepidoptera are negative, the long-term effects (> 1 year) of reduced abundance of gypsy moth larvae may be beneficial for some native species. Although Btk application and defoliation reduce abundance of native Lepidoptera, environmental conditions such as weather may have a greater influence on population fluctuations.

During 1992 and 1993, we studied the life cycle of Lambdina athasaria (Walker) developing on eastern hemlock, Tsuga canadensis (L.) Carrière, in Connecticut. The geometrid was univoltine, overwintering as a pupa. Adults emerged during 4 weeks in May and June after hemlock budbreak. Males emerged significantly earlier than females, and both sexes emerged earlier in 1993 than in 1992. Males flew for 4–5 weeks annually. Based on measurements of head capsule width, larvae had five or six instars, which fed from June to October. Early instars ate new growth, and older ones fed on old growth. Until mid-August, larval development was more advanced in 1993 than in 1992. Larvae descended from trees in September and October to pupate in the duff beneath trees. Lambdina athasaria can be distinguished from congeneric species that feed on conifers by its overwintering stage, flight period, larval size, and host.

Overwintering pear psylla, Cacopsylla pyricola (Foerster), were misted with water or with one of several dilute solutions of water and surfactant, and then exposed to a range of subzero temperatures for 24 h. Misted psylla had significantly greater mortality than unmisted controls. Increases in mortality occurred at temperatures as warm as −6°C, a temperature well within the range of conditions in the field. At extreme low temperatures (−18°C) there was virtually no mortality in the unmisted controls, whereas mortality approached or reached 100% in several of the misted groups. Temperatures necessary to kill 50% of insects estimated for topically treated psylla ranged between −2.6 and −12.7°C for surfactant-treated insects, and below −18°C for water-treated or control insects. The possibility of using surfactants and water for control of overwintering pear psylla is discussed.

Neothelaxes gen.nov., type-species N. viticola sp.nov., as well as N. parthenocissi sp.nov., are described. The host-plant of the two species is Parthenocissus semicordata. The taxonomic position of the aphids is discussed.